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Wikipedia

LDL receptor

The low-density lipoprotein receptor (LDL-R) is a mosaic protein of 839 amino acids (after removal of 21-amino acid signal peptide)[5] that mediates the endocytosis of cholesterol-rich low-density lipoprotein (LDL). It is a cell-surface receptor that recognizes apolipoprotein B100 (ApoB100), which is embedded in the outer phospholipid layer of very low-density lipoprotein (VLDL), their remnants—i.e. intermediate-density lipoprotein (IDL), and LDL particles. The receptor also recognizes apolipoprotein E (ApoE) which is found in chylomicron remnants and IDL. In humans, the LDL receptor protein is encoded by the LDLR gene on chromosome 19.[6][7][8] It belongs to the low density lipoprotein receptor gene family.[9] It is most significantly expressed in bronchial epithelial cells and adrenal gland and cortex tissue.[10]

LDLR
Available structures
PDBOrtholog search: PDBe RCSB
Identifiers
AliasesLDLR, FH, FHC, LDLCQ2, low density lipoprotein receptor, FHCL1
External IDsOMIM: 606945 MGI: 96765 HomoloGene: 55469 GeneCards: LDLR
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_001252658
NM_001252659
NM_010700

RefSeq (protein)

NP_000518
NP_001182727
NP_001182728
NP_001182729
NP_001182732

NP_001239587
NP_001239588
NP_034830

Location (UCSC)Chr 19: 11.09 – 11.13 MbChr 9: 21.63 – 21.66 Mb
PubMed search[3][4]
Wikidata
View/Edit HumanView/Edit Mouse

Michael S. Brown and Joseph L. Goldstein were awarded the 1985 Nobel Prize in Physiology or Medicine for their identification of LDL-R[11] and its relation to cholesterol metabolism and familial hypercholesterolemia.[12] Disruption of LDL-R can lead to higher LDL-cholesterol as well as increasing the risk of related diseases. Individuals with disruptive mutations (defined as nonsense, splice site, or indel frameshift) in LDLR have an average LDL-cholesterol of 279 mg/dL, compared with 135 mg/dL for individuals with neither disruptive nor deleterious mutations. Disruptive mutations were 13 times more common in individuals with early-onset myocardial infarction or coronary artery disease than in individuals without either disease.[13]

Structure edit

Gene edit

The LDLR gene resides on chromosome 19 at the band 19p13.2 and is split into 18 exons.[8] Exon 1 contains a signal sequence that localises the receptor to the endoplasmic reticulum for transport to the cell surface. Beyond this, exons 2-6 code the ligand binding region; 7-14 code the epidermal growth factor (EGF) domain; 15 codes the oligosaccharide rich region; 16 (and some of 17) code the membrane spanning region; and 18 (with the rest of 17) code the cytosolic domain.

This gene produces 6 isoforms through alternative splicing.[14]

Protein edit

This protein belongs to the LDLR family and is made up of a number of functionally distinct domains, including 3 EGF-like domains, 7 LDL-R class A domains, and 6 LDL-R class B repeats.[14]

The N-terminal domain of the LDL receptor, which is responsible for ligand binding, is composed of seven sequence repeats (~50% identical). Each repeat, referred to as a class A repeat or LDL-A, contains roughly 40 amino acids, including 6 cysteine residues that form disulfide bonds within the repeat. Additionally, each repeat has highly conserved acidic residues which it uses to coordinate a single calcium ion in an octahedral lattice. Both the disulfide bonds and calcium coordination are necessary for the structural integrity of the domain during the receptor's repeated trips to the highly acidic interior of the endosome. The exact mechanism of interaction between the class A repeats and ligand (LDL) is unknown, but it is thought that the repeats act as "grabbers" to hold the LDL. Binding of ApoB requires repeats 2-7 while binding ApoE requires only repeat 5 (thought to be the ancestral repeat).

Next to the ligand binding domain is an EGF precursor homology domain (EGFP domain). This shows approximately 30% homology with the EGF precursor gene. There are three "growth factor" repeats; A, B and C. A and B are closely linked while C is separated by the YWTD repeat region, which adopts a beta-propeller conformation (LDL-R class B domain). It is thought that this region is responsible for the pH-dependent conformational shift that causes bound LDL to be released in the endosome.

A third domain of the protein is rich in O-linked oligosaccharides but appears to show little function. Knockout experiments have confirmed that no significant loss of activity occurs without this domain. It has been speculated that the domain may have ancestrally acted as a spacer to push the receptor beyond the extracellular matrix.

The single transmembrane domain of 22 (mostly) non-polar residues crosses the plasma membrane in a single alpha helix.

The cytosolic C-terminal domain contains ~50 amino acids, including a signal sequence important for localizing the receptors to clathrin-coated pits and for triggering receptor-mediated endocytosis after binding. Portions of the cytosolic sequence have been found in other lipoprotein receptors, as well as in more distant receptor relatives.[15][16][17]

Mutations edit

Loss-of-function mutations in the gene encoding the LDL receptor are known to cause familial hypercholesterolaemia.

There are 5 broad classes of mutation of the LDL receptor:

  • Class 1 mutations affect the synthesis of the receptor in the endoplasmic reticulum (ER).
  • Class 2 mutations prevent proper transport to the Golgi body needed for modifications to the receptor.
    • e.g. a truncation of the receptor protein at residue number 660 leads to domains 3,4 and 5 of the EGF precursor domain being missing. This precludes the movement of the receptor from the ER to the Golgi, and leads to degradation of the receptor protein.
  • Class 3 mutations stop the binding of LDL to the receptor.
    • e.g. repeat 6 of the ligand binding domain (N-terminal, extracellular fluid) is deleted.
  • Class 4 mutations inhibit the internalization of the receptor-ligand complex.
    • e.g. "JD" mutant results from a single point mutation in the NPVY domain (C-terminal, cytosolic; C residue converted to a Y, residue number 807). This domain recruits clathrin and other proteins responsible for the endocytosis of LDL, therefore this mutation inhibits LDL internalization.
  • Class 5 mutations give rise to receptors that cannot recycle properly. This leads to a relatively mild phenotype as receptors are still present on the cell surface (but all must be newly synthesised).[18]

Gain-of-function mutations decrease LDL levels and are a target of research to develop a gene therapy to treat refractory hypercholesterolemia.[19]

Function edit

LDL receptor mediates the endocytosis of cholesterol-rich LDL and thus maintains the plasma level of LDL.[20] This occurs in all nucleated cells, but mainly in the liver which removes ~70% of LDL from the circulation. LDL receptors are clustered in clathrin-coated pits, and coated pits pinch off from the surface to form coated endocytic vesicles that carry LDL into the cell.[21] After internalization, the receptors dissociate from their ligands when they are exposed to lower pH in endosomes. After dissociation, the receptor folds back on itself to obtain a closed conformation and recycles to the cell surface.[22] The rapid recycling of LDL receptors provides an efficient mechanism for delivery of cholesterol to cells.[23][24] It was also reported that by association with lipoprotein in the blood, viruses such as hepatitis C virus, Flaviviridae viruses and bovine viral diarrheal virus could enter cells indirectly via LDLR-mediated endocytosis.[25] LDLR has been identified as the primary mode of entry for the Vesicular stomatitis virus in mice and humans.[26] In addition, LDLR modulation is associated with early atherosclerosis-related lymphatic dysfunction.[27] Synthesis of receptors in the cell is regulated by the level of free intracellular cholesterol; if it is in excess for the needs of the cell then the transcription of the receptor gene will be inhibited.[28] LDL receptors are translated by ribosomes on the endoplasmic reticulum and are modified by the Golgi apparatus before travelling in vesicles to the cell surface.

Clinical significance edit

In humans, LDL is directly involved in the development of atherosclerosis, which is the process responsible for the majority of cardiovascular diseases, due to accumulation of LDL-cholesterol in the blood [citation needed]. Hyperthyroidism may be associated with hypocholesterolemia via upregulation of the LDL receptor, and hypothyroidism with the converse. A vast number of studies have described the relevance of LDL receptors in the pathophysiology of atherosclerosis, metabolic syndrome, and steatohepatitis.[29][30] Previously, rare mutations in LDL-genes have been shown to contribute to myocardial infarction risk in individual families, whereas common variants at more than 45 loci have been associated with myocardial infarction risk in the population. When compared with non-carriers, LDLR mutation carriers had higher plasma LDL cholesterol, whereas APOA5 mutation carriers had higher plasma triglycerides.[31] Recent evidence has connected MI risk with coding-sequence mutations at two genes functionally related to APOA5, namely lipoprotein lipase and apolipoprotein C-III.[32][33] Combined, these observations suggest that, as well as LDL cholesterol, disordered metabolism of triglyceride-rich lipoproteins contributes to MI risk. Overall, LDLR has a high clinical relevance in blood lipids.[34][35]

Clinical marker edit

A multi-locus genetic risk score study based on a combination of 27 loci, including the LDLR gene, identified individuals at increased risk for both incident and recurrent coronary artery disease events, as well as an enhanced clinical benefit from statin therapy. The study was based on a community cohort study (the Malmö Diet and Cancer study) and four additional randomized controlled trials of primary prevention cohorts (JUPITER and ASCOT) and secondary prevention cohorts (CARE and PROVE IT-TIMI 22).[36]

Interactive pathway map edit

Click on genes, proteins and metabolites below to link to respective articles. [§ 1]

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|alt=Statin pathway edit]]
Statin pathway edit
  1. ^ The interactive pathway map can be edited at WikiPathways: "Statin_Pathway_WP430".

References edit

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  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000032193 – Ensembl, May 2017
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  4. ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
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  6. ^ Francke U, Brown MS, Goldstein JL (May 1984). "Assignment of the human gene for the low density lipoprotein receptor to chromosome 19: synteny of a receptor, a ligand, and a genetic disease". Proceedings of the National Academy of Sciences of the United States of America. 81 (9): 2826–30. Bibcode:1984PNAS...81.2826F. doi:10.1073/pnas.81.9.2826. PMC 345163. PMID 6326146.
  7. ^ Lindgren V, Luskey KL, Russell DW, Francke U (December 1985). "Human genes involved in cholesterol metabolism: chromosomal mapping of the loci for the low density lipoprotein receptor and 3-hydroxy-3-methylglutaryl-coenzyme A reductase with cDNA probes". Proceedings of the National Academy of Sciences of the United States of America. 82 (24): 8567–71. Bibcode:1985PNAS...82.8567L. doi:10.1073/pnas.82.24.8567. PMC 390958. PMID 3866240.
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  16. ^ Brown MS, Herz J, Goldstein JL (August 1997). "LDL-receptor structure. Calcium cages, acid baths and recycling receptors". Nature. 388 (6643): 629–30. Bibcode:1997Natur.388..629B. doi:10.1038/41672. PMID 9262394. S2CID 33590160.
  17. ^ Gent J, Braakman I (October 2004). "Low-density lipoprotein receptor structure and folding". Cellular and Molecular Life Sciences. 61 (19–20): 2461–70. doi:10.1007/s00018-004-4090-3. PMID 15526154. S2CID 21235282.
  18. ^ . LOVD v.1.1.0 - Leiden Open Variation Database. Archived from the original on 2016-01-28. Retrieved 2013-10-17.
  19. ^ Srivastava RA (December 2023). "New opportunities in the management and treatment of refractory hypercholesterolemia using in vivo CRISPR-mediated genome/base editing". Nutrition, Metabolism and Cardiovascular Diseases. 33 (12): 2317–2325. doi:10.1016/j.numecd.2023.08.010. PMID 37805309.
  20. ^ Leren TP (November 2014). "Sorting an LDL receptor with bound PCSK9 to intracellular degradation". Atherosclerosis. 237 (1): 76–81. doi:10.1016/j.atherosclerosis.2014.08.038. PMID 25222343.
  21. ^ Goldstein JL, Brown MS (April 2009). "The LDL receptor". Arteriosclerosis, Thrombosis, and Vascular Biology. 29 (4): 431–8. doi:10.1161/ATVBAHA.108.179564. PMC 2740366. PMID 19299327.
  22. ^ Rudenko G, Henry L, Henderson K, Ichtchenko K, Brown MS, Goldstein JL, et al. (December 2002). "Structure of the LDL receptor extracellular domain at endosomal pH". Science. 298 (5602): 2353–8. Bibcode:2002Sci...298.2353R. doi:10.1126/science.1078124. PMID 12459547. S2CID 17712211.
  23. ^ Basu SK, Goldstein JL, Anderson RG, Brown MS (May 1981). "Monensin interrupts the recycling of low density lipoprotein receptors in human fibroblasts". Cell. 24 (2): 493–502. doi:10.1016/0092-8674(81)90340-8. PMID 6263497. S2CID 29553611.
  24. ^ Brown MS, Anderson RG, Goldstein JL (March 1983). "Recycling receptors: the round-trip itinerary of migrant membrane proteins". Cell. 32 (3): 663–7. doi:10.1016/0092-8674(83)90052-1. PMID 6299572. S2CID 34919831.
  25. ^ Agnello V, Abel G, Elfahal M, Knight GB, Zhang QX (October 1999). "Hepatitis C virus and other flaviviridae viruses enter cells via low density lipoprotein receptor". Proceedings of the National Academy of Sciences of the United States of America. 96 (22): 12766–71. Bibcode:1999PNAS...9612766A. doi:10.1073/pnas.96.22.12766. PMC 23090. PMID 10535997.
  26. ^ Finkelshtein D, Werman A, Novick D, Barak S, Rubinstein M (April 2013). "LDL receptor and its family members serve as the cellular receptors for vesicular stomatitis virus". Proceedings of the National Academy of Sciences of the United States of America. 110 (18): 7306–11. Bibcode:2013PNAS..110.7306F. doi:10.1073/pnas.1214441110. PMC 3645523. PMID 23589850.
  27. ^ Milasan A, Dallaire F, Mayer G, Martel C (2016-01-01). "Effects of LDL Receptor Modulation on Lymphatic Function". Scientific Reports. 6: 27862. Bibcode:2016NatSR...627862M. doi:10.1038/srep27862. PMC 4899717. PMID 27279328.
  28. ^ Smith JR, Osborne TF, Goldstein JL, Brown MS (Feb 1990). "Identification of nucleotides responsible for enhancer activity of sterol regulatory element in low density lipoprotein receptor gene". The Journal of Biological Chemistry. 265 (4): 2306–10. doi:10.1016/S0021-9258(19)39976-4. PMID 2298751. S2CID 26062629.
  29. ^ Hsieh J, Koseki M, Molusky MM, Yakushiji E, Ichi I, Westerterp M, et al. (July 2016). "TTC39B deficiency stabilizes LXR reducing both atherosclerosis and steatohepatitis". Nature. 535 (7611): 303–7. Bibcode:2016Natur.535..303H. doi:10.1038/nature18628. PMC 4947007. PMID 27383786.
  30. ^ Walter K, Min JL, Huang J, Crooks L, Memari Y, McCarthy S, et al. (October 2015). "The UK10K project identifies rare variants in health and disease". Nature. 526 (7571): 82–90. Bibcode:2015Natur.526...82T. doi:10.1038/nature14962. PMC 4773891. PMID 26367797.
  31. ^ Rose-Hellekant TA, Schroeder MD, Brockman JL, Zhdankin O, Bolstad R, Chen KS, et al. (August 2007). "Estrogen receptor-positive mammary tumorigenesis in TGFalpha transgenic mice progresses with progesterone receptor loss". Oncogene. 26 (36): 5238–46. doi:10.1038/sj.onc.1210340. PMC 2587149. PMID 17334393.
  32. ^ Crosby J, Peloso GM, Auer PL, Crosslin DR, Stitziel NO, Lange LA, et al. (July 2014). "Loss-of-function mutations in APOC3, triglycerides, and coronary disease". The New England Journal of Medicine. 371 (1): 22–31. doi:10.1056/NEJMoa1307095. PMC 4180269. PMID 24941081.
  33. ^ Jørgensen AB, Frikke-Schmidt R, Nordestgaard BG, Tybjærg-Hansen A (July 2014). "Loss-of-function mutations in APOC3 and risk of ischemic vascular disease". The New England Journal of Medicine. 371 (1): 32–41. doi:10.1056/NEJMoa1308027. PMID 24941082. S2CID 26995834.
  34. ^ Shuldiner AR, Pollin TI (August 2010). "Genomics: Variations in blood lipids". Nature. 466 (7307): 703–4. Bibcode:2010Natur.466..703S. doi:10.1038/466703a. PMID 20686562. S2CID 205057802.
  35. ^ Teslovich TM, Musunuru K, Smith AV, Edmondson AC, Stylianou IM, Koseki M, et al. (August 2010). "Biological, clinical and population relevance of 95 loci for blood lipids". Nature. 466 (7307): 707–13. Bibcode:2010Natur.466..707T. doi:10.1038/nature09270. PMC 3039276. PMID 20686565.
  36. ^ Mega JL, Stitziel NO, Smith JG, Chasman DI, Caulfield MJ, Devlin JJ, et al. (June 2015). "Genetic risk, coronary heart disease events, and the clinical benefit of statin therapy: an analysis of primary and secondary prevention trials". Lancet. 385 (9984): 2264–71. doi:10.1016/S0140-6736(14)61730-X. PMC 4608367. PMID 25748612.

Further reading edit

  • Brown MS, Goldstein JL (July 1979). "Receptor-mediated endocytosis: insights from the lipoprotein receptor system". Proceedings of the National Academy of Sciences of the United States of America. 76 (7): 3330–7. Bibcode:1979PNAS...76.3330B. doi:10.1073/pnas.76.7.3330. PMC 383819. PMID 226968.
  • Hobbs HH, Brown MS, Goldstein JL (1993). "Molecular genetics of the LDL receptor gene in familial hypercholesterolemia". Human Mutation. 1 (6): 445–66. doi:10.1002/humu.1380010602. PMID 1301956. S2CID 5756814.
  • Fogelman AM, Van Lenten BJ, Warden C, Haberland ME, Edwards PA (1989). "Macrophage lipoprotein receptors". Journal of Cell Science. Supplement. 9: 135–49. doi:10.1242/jcs.1988.supplement_9.7. PMID 2855802.
  • Barrett PH, Watts GF (March 2002). "Shifting the LDL-receptor paradigm in familial hypercholesterolemia: novel insights from recent kinetic studies of apolipoprotein B-100 metabolism". Atherosclerosis. Supplements. 2 (3): 1–4. doi:10.1016/S1567-5688(01)00012-5. PMID 11923121.
  • May P, Bock HH, Herz J (April 2003). "Integration of endocytosis and signal transduction by lipoprotein receptors". Science's STKE. 2003 (176): PE12. doi:10.1126/stke.2003.176.pe12. PMID 12671190. S2CID 24468290.
  • Gent J, Braakman I (October 2004). "Low-density lipoprotein receptor structure and folding". Cellular and Molecular Life Sciences. 61 (19–20): 2461–70. doi:10.1007/s00018-004-4090-3. PMID 15526154. S2CID 21235282.

External links edit

  • Description of LDL receptor pathway at the Brown - Goldstein Laboratory webpage
  • LDL+Receptor at the U.S. National Library of Medicine Medical Subject Headings (MeSH)

receptor, density, lipoprotein, receptor, mosaic, protein, amino, acids, after, removal, amino, acid, signal, peptide, that, mediates, endocytosis, cholesterol, rich, density, lipoprotein, cell, surface, receptor, that, recognizes, apolipoprotein, b100, apob10. The low density lipoprotein receptor LDL R is a mosaic protein of 839 amino acids after removal of 21 amino acid signal peptide 5 that mediates the endocytosis of cholesterol rich low density lipoprotein LDL It is a cell surface receptor that recognizes apolipoprotein B100 ApoB100 which is embedded in the outer phospholipid layer of very low density lipoprotein VLDL their remnants i e intermediate density lipoprotein IDL and LDL particles The receptor also recognizes apolipoprotein E ApoE which is found in chylomicron remnants and IDL In humans the LDL receptor protein is encoded by the LDLR gene on chromosome 19 6 7 8 It belongs to the low density lipoprotein receptor gene family 9 It is most significantly expressed in bronchial epithelial cells and adrenal gland and cortex tissue 10 LDLRAvailable structuresPDBOrtholog search PDBe RCSBList of PDB id codes1AJJ 1D2J 1F5Y 1HJ7 1HZ8 1I0U 1IJQ 1LDL 1LDR 1N7D 1XFE 2FCW 2KRI 2LGP 2W2M 2W2N 2W2O 2W2P 2W2Q 3BPS 3GCW 3GCX 3M0C 3SO6 2M7P 2MG9 3P5B 3P5C 4NE9IdentifiersAliasesLDLR FH FHC LDLCQ2 low density lipoprotein receptor FHCL1External IDsOMIM 606945 MGI 96765 HomoloGene 55469 GeneCards LDLRGene location Human Chr Chromosome 19 human 1 Band19p13 2Start11 089 462 bp 1 End11 133 820 bp 1 Gene location Mouse Chr Chromosome 9 mouse 2 Band9 A3 9 7 87 cMStart21 634 779 bp 2 End21 661 215 bp 2 RNA expression patternBgeeHumanMouse ortholog Top expressed inlower lobe of lungright adrenal glandleft adrenal glandstromal cell of endometriumupper lobe of lungupper lobe of left lungmucosa of urinary bladderright lungislet of Langerhansleft uterine tubeTop expressed incumulus cellsciatic nerveascending aortaotic placodeislet of Langerhansadrenal glandleft lobe of liveririsankle jointciliary bodyMore reference expression dataBioGPSMore reference expression dataGene ontologyMolecular functioncalcium ion binding clathrin heavy chain binding virus receptor activity protein binding protease binding identical protein binding very low density lipoprotein particle receptor activity low density lipoprotein particle receptor activity low density lipoprotein particle binding amyloid beta bindingCellular componentintegral component of membrane clathrin coated endocytic vesicle membrane endosome late endosome Golgi apparatus membrane receptor complex plasma membrane apical part of cell integral component of plasma membrane cell surface basolateral plasma membrane early endosome low density lipoprotein particle clathrin coated pit lysosome PCSK9 LDLR complex endosome membrane external side of plasma membrane extracellular space endolysosome membrane sorting endosome intracellular anatomical structure somatodendritic compartmentBiological processpositive regulation of triglyceride biosynthetic process regulation of phosphatidylcholine catabolic process steroid metabolic process lipid transport endocytosis lipid metabolism phospholipid transport cholesterol transport cholesterol metabolic process lipoprotein catabolic process intestinal cholesterol absorption transport viral entry into host cell cholesterol homeostasis viral process positive regulation of gene expression positive regulation of inflammatory response lipoprotein metabolic process cellular response to fatty acid negative regulation of gene expression membrane organization cholesterol import cellular response to low density lipoprotein particle stimulus receptor mediated endocytosis involved in cholesterol transport chylomicron remnant clearance low density lipoprotein particle clearance receptor mediated endocytosis phagocytosis long term memory plasma lipoprotein particle clearance high density lipoprotein particle clearance regulation of protein metabolic process negative regulation of protein metabolic process response to caloric restriction negative regulation of astrocyte activation regulation of cholesterol metabolic process amyloid beta clearance amyloid beta clearance by cellular catabolic process negative regulation of microglial cell activation positive regulation of lysosomal protein catabolic process negative regulation of amyloid fibril formation artery morphogenesisSources Amigo QuickGOOrthologsSpeciesHumanMouseEntrez394916835EnsemblENSG00000130164ENSMUSG00000032193UniProtP01130P35951RefSeq mRNA NM 000527NM 001195798NM 001195799NM 001195800NM 001195802NM 001195803NM 001252658NM 001252659NM 010700RefSeq protein NP 000518NP 001182727NP 001182728NP 001182729NP 001182732NP 001239587NP 001239588NP 034830Location UCSC Chr 19 11 09 11 13 MbChr 9 21 63 21 66 MbPubMed search 3 4 WikidataView Edit HumanView Edit Mouse Michael S Brown and Joseph L Goldstein were awarded the 1985 Nobel Prize in Physiology or Medicine for their identification of LDL R 11 and its relation to cholesterol metabolism and familial hypercholesterolemia 12 Disruption of LDL R can lead to higher LDL cholesterol as well as increasing the risk of related diseases Individuals with disruptive mutations defined as nonsense splice site or indel frameshift in LDLR have an average LDL cholesterol of 279 mg dL compared with 135 mg dL for individuals with neither disruptive nor deleterious mutations Disruptive mutations were 13 times more common in individuals with early onset myocardial infarction or coronary artery disease than in individuals without either disease 13 Contents 1 Structure 1 1 Gene 1 2 Protein 1 3 Mutations 2 Function 3 Clinical significance 3 1 Clinical marker 4 Interactive pathway map 5 References 6 Further reading 7 External linksStructure editGene edit The LDLR gene resides on chromosome 19 at the band 19p13 2 and is split into 18 exons 8 Exon 1 contains a signal sequence that localises the receptor to the endoplasmic reticulum for transport to the cell surface Beyond this exons 2 6 code the ligand binding region 7 14 code the epidermal growth factor EGF domain 15 codes the oligosaccharide rich region 16 and some of 17 code the membrane spanning region and 18 with the rest of 17 code the cytosolic domain This gene produces 6 isoforms through alternative splicing 14 Protein edit This protein belongs to the LDLR family and is made up of a number of functionally distinct domains including 3 EGF like domains 7 LDL R class A domains and 6 LDL R class B repeats 14 The N terminal domain of the LDL receptor which is responsible for ligand binding is composed of seven sequence repeats 50 identical Each repeat referred to as a class A repeat or LDL A contains roughly 40 amino acids including 6 cysteine residues that form disulfide bonds within the repeat Additionally each repeat has highly conserved acidic residues which it uses to coordinate a single calcium ion in an octahedral lattice Both the disulfide bonds and calcium coordination are necessary for the structural integrity of the domain during the receptor s repeated trips to the highly acidic interior of the endosome The exact mechanism of interaction between the class A repeats and ligand LDL is unknown but it is thought that the repeats act as grabbers to hold the LDL Binding of ApoB requires repeats 2 7 while binding ApoE requires only repeat 5 thought to be the ancestral repeat Next to the ligand binding domain is an EGF precursor homology domain EGFP domain This shows approximately 30 homology with the EGF precursor gene There are three growth factor repeats A B and C A and B are closely linked while C is separated by the YWTD repeat region which adopts a beta propeller conformation LDL R class B domain It is thought that this region is responsible for the pH dependent conformational shift that causes bound LDL to be released in the endosome A third domain of the protein is rich in O linked oligosaccharides but appears to show little function Knockout experiments have confirmed that no significant loss of activity occurs without this domain It has been speculated that the domain may have ancestrally acted as a spacer to push the receptor beyond the extracellular matrix The single transmembrane domain of 22 mostly non polar residues crosses the plasma membrane in a single alpha helix The cytosolic C terminal domain contains 50 amino acids including a signal sequence important for localizing the receptors to clathrin coated pits and for triggering receptor mediated endocytosis after binding Portions of the cytosolic sequence have been found in other lipoprotein receptors as well as in more distant receptor relatives 15 16 17 Mutations edit Loss of function mutations in the gene encoding the LDL receptor are known to cause familial hypercholesterolaemia There are 5 broad classes of mutation of the LDL receptor Class 1 mutations affect the synthesis of the receptor in the endoplasmic reticulum ER Class 2 mutations prevent proper transport to the Golgi body needed for modifications to the receptor e g a truncation of the receptor protein at residue number 660 leads to domains 3 4 and 5 of the EGF precursor domain being missing This precludes the movement of the receptor from the ER to the Golgi and leads to degradation of the receptor protein Class 3 mutations stop the binding of LDL to the receptor e g repeat 6 of the ligand binding domain N terminal extracellular fluid is deleted Class 4 mutations inhibit the internalization of the receptor ligand complex e g JD mutant results from a single point mutation in the NPVY domain C terminal cytosolic C residue converted to a Y residue number 807 This domain recruits clathrin and other proteins responsible for the endocytosis of LDL therefore this mutation inhibits LDL internalization Class 5 mutations give rise to receptors that cannot recycle properly This leads to a relatively mild phenotype as receptors are still present on the cell surface but all must be newly synthesised 18 Gain of function mutations decrease LDL levels and are a target of research to develop a gene therapy to treat refractory hypercholesterolemia 19 Function editLDL receptor mediates the endocytosis of cholesterol rich LDL and thus maintains the plasma level of LDL 20 This occurs in all nucleated cells but mainly in the liver which removes 70 of LDL from the circulation LDL receptors are clustered in clathrin coated pits and coated pits pinch off from the surface to form coated endocytic vesicles that carry LDL into the cell 21 After internalization the receptors dissociate from their ligands when they are exposed to lower pH in endosomes After dissociation the receptor folds back on itself to obtain a closed conformation and recycles to the cell surface 22 The rapid recycling of LDL receptors provides an efficient mechanism for delivery of cholesterol to cells 23 24 It was also reported that by association with lipoprotein in the blood viruses such as hepatitis C virus Flaviviridae viruses and bovine viral diarrheal virus could enter cells indirectly via LDLR mediated endocytosis 25 LDLR has been identified as the primary mode of entry for the Vesicular stomatitis virus in mice and humans 26 In addition LDLR modulation is associated with early atherosclerosis related lymphatic dysfunction 27 Synthesis of receptors in the cell is regulated by the level of free intracellular cholesterol if it is in excess for the needs of the cell then the transcription of the receptor gene will be inhibited 28 LDL receptors are translated by ribosomes on the endoplasmic reticulum and are modified by the Golgi apparatus before travelling in vesicles to the cell surface Clinical significance editIn humans LDL is directly involved in the development of atherosclerosis which is the process responsible for the majority of cardiovascular diseases due to accumulation of LDL cholesterol in the blood citation needed Hyperthyroidism may be associated with hypocholesterolemia via upregulation of the LDL receptor and hypothyroidism with the converse A vast number of studies have described the relevance of LDL receptors in the pathophysiology of atherosclerosis metabolic syndrome and steatohepatitis 29 30 Previously rare mutations in LDL genes have been shown to contribute to myocardial infarction risk in individual families whereas common variants at more than 45 loci have been associated with myocardial infarction risk in the population When compared with non carriers LDLR mutation carriers had higher plasma LDL cholesterol whereas APOA5 mutation carriers had higher plasma triglycerides 31 Recent evidence has connected MI risk with coding sequence mutations at two genes functionally related to APOA5 namely lipoprotein lipase and apolipoprotein C III 32 33 Combined these observations suggest that as well as LDL cholesterol disordered metabolism of triglyceride rich lipoproteins contributes to MI risk Overall LDLR has a high clinical relevance in blood lipids 34 35 Clinical marker edit A multi locus genetic risk score study based on a combination of 27 loci including the LDLR gene identified individuals at increased risk for both incident and recurrent coronary artery disease events as well as an enhanced clinical benefit from statin therapy The study was based on a community cohort study the Malmo Diet and Cancer study and four additional randomized controlled trials of primary prevention cohorts JUPITER and ASCOT and secondary prevention cohorts CARE and PROVE IT TIMI 22 36 Interactive pathway map editClick on genes proteins and metabolites below to link to respective articles 1 File nbsp nbsp alt Statin pathway edit Statin pathway edit The interactive pathway map can be edited at WikiPathways Statin Pathway WP430 References edit a b c GRCh38 Ensembl release 89 ENSG00000130164 Ensembl May 2017 a b c GRCm38 Ensembl release 89 ENSMUSG00000032193 Ensembl May 2017 Human PubMed Reference National Center for Biotechnology Information U S National Library of Medicine Mouse PubMed Reference National Center for Biotechnology Information U S National Library of Medicine Sudhof TC Goldstein JL Brown MS Russell DW May 1985 The LDL receptor gene a mosaic of exons shared with different proteins Science 228 4701 815 22 Bibcode 1985Sci 228 815S doi 10 1126 science 2988123 PMC 4450672 PMID 2988123 Francke U Brown MS Goldstein JL May 1984 Assignment of the human gene for the low density lipoprotein receptor to chromosome 19 synteny of a receptor a ligand and a genetic disease Proceedings of the National Academy of Sciences of the United States of America 81 9 2826 30 Bibcode 1984PNAS 81 2826F doi 10 1073 pnas 81 9 2826 PMC 345163 PMID 6326146 Lindgren V Luskey KL Russell DW Francke U December 1985 Human genes involved in cholesterol metabolism chromosomal mapping of the loci for the low density lipoprotein receptor and 3 hydroxy 3 methylglutaryl coenzyme A reductase with cDNA probes Proceedings of the National Academy of Sciences of the United States of America 82 24 8567 71 Bibcode 1985PNAS 82 8567L doi 10 1073 pnas 82 24 8567 PMC 390958 PMID 3866240 a b LDLR low density lipoprotein receptor Homo sapiens human Gene NCBI www ncbi nlm nih gov Retrieved 2016 10 10 Nykjaer A Willnow TE June 2002 The low density lipoprotein receptor gene family a cellular Swiss army knife Trends in Cell Biology 12 6 273 80 doi 10 1016 S0962 8924 02 02282 1 PMID 12074887 BioGPS your Gene Portal System biogps org Retrieved 2016 10 10 The Nobel Prize in Physiology or Medicine 1985 Press release The Royal Swedish Academy of Science 1985 Retrieved 2010 07 01 Brown MS Goldstein JL November 1984 How LDL receptors influence cholesterol and atherosclerosis Scientific American 251 5 58 66 Bibcode 1984SciAm 251c 52K doi 10 1038 scientificamerican0984 52 PMID 6390676 Do R Stitziel NO Won HH Jorgensen AB Duga S Angelica Merlini P et al February 2015 Exome sequencing identifies rare LDLR and APOA5 alleles conferring risk for myocardial infarction Nature 518 7537 102 6 Bibcode 2015Natur 518 102 doi 10 1038 nature13917 PMC 4319990 PMID 25487149 a b LDLR Low density lipoprotein receptor precursor Homo sapiens Human LDLR gene amp protein www uniprot org Retrieved 2016 10 10 Yamamoto T Davis CG Brown MS Schneider WJ Casey ML Goldstein JL et al November 1984 The human LDL receptor a cysteine rich protein with multiple Alu sequences in its mRNA Cell 39 1 27 38 doi 10 1016 0092 8674 84 90188 0 PMID 6091915 S2CID 25822170 Brown MS Herz J Goldstein JL August 1997 LDL receptor structure Calcium cages acid baths and recycling receptors Nature 388 6643 629 30 Bibcode 1997Natur 388 629B doi 10 1038 41672 PMID 9262394 S2CID 33590160 Gent J Braakman I October 2004 Low density lipoprotein receptor structure and folding Cellular and Molecular Life Sciences 61 19 20 2461 70 doi 10 1007 s00018 004 4090 3 PMID 15526154 S2CID 21235282 Low Density Lipoprotein Receptor LOVD v 1 1 0 Leiden Open Variation Database Archived from the original on 2016 01 28 Retrieved 2013 10 17 Srivastava RA December 2023 New opportunities in the management and treatment of refractory hypercholesterolemia using in vivo CRISPR mediated genome base editing Nutrition Metabolism and Cardiovascular Diseases 33 12 2317 2325 doi 10 1016 j numecd 2023 08 010 PMID 37805309 Leren TP November 2014 Sorting an LDL receptor with bound PCSK9 to intracellular degradation Atherosclerosis 237 1 76 81 doi 10 1016 j atherosclerosis 2014 08 038 PMID 25222343 Goldstein JL Brown MS April 2009 The LDL receptor Arteriosclerosis Thrombosis and Vascular Biology 29 4 431 8 doi 10 1161 ATVBAHA 108 179564 PMC 2740366 PMID 19299327 Rudenko G Henry L Henderson K Ichtchenko K Brown MS Goldstein JL et al December 2002 Structure of the LDL receptor extracellular domain at endosomal pH Science 298 5602 2353 8 Bibcode 2002Sci 298 2353R doi 10 1126 science 1078124 PMID 12459547 S2CID 17712211 Basu SK Goldstein JL Anderson RG Brown MS May 1981 Monensin interrupts the recycling of low density lipoprotein receptors in human fibroblasts Cell 24 2 493 502 doi 10 1016 0092 8674 81 90340 8 PMID 6263497 S2CID 29553611 Brown MS Anderson RG Goldstein JL March 1983 Recycling receptors the round trip itinerary of migrant membrane proteins Cell 32 3 663 7 doi 10 1016 0092 8674 83 90052 1 PMID 6299572 S2CID 34919831 Agnello V Abel G Elfahal M Knight GB Zhang QX October 1999 Hepatitis C virus and other flaviviridae viruses enter cells via low density lipoprotein receptor Proceedings of the National Academy of Sciences of the United States of America 96 22 12766 71 Bibcode 1999PNAS 9612766A doi 10 1073 pnas 96 22 12766 PMC 23090 PMID 10535997 Finkelshtein D Werman A Novick D Barak S Rubinstein M April 2013 LDL receptor and its family members serve as the cellular receptors for vesicular stomatitis virus Proceedings of the National Academy of Sciences of the United States of America 110 18 7306 11 Bibcode 2013PNAS 110 7306F doi 10 1073 pnas 1214441110 PMC 3645523 PMID 23589850 Milasan A Dallaire F Mayer G Martel C 2016 01 01 Effects of LDL Receptor Modulation on Lymphatic Function Scientific Reports 6 27862 Bibcode 2016NatSR 627862M doi 10 1038 srep27862 PMC 4899717 PMID 27279328 Smith JR Osborne TF Goldstein JL Brown MS Feb 1990 Identification of nucleotides responsible for enhancer activity of sterol regulatory element in low density lipoprotein receptor gene The Journal of Biological Chemistry 265 4 2306 10 doi 10 1016 S0021 9258 19 39976 4 PMID 2298751 S2CID 26062629 Hsieh J Koseki M Molusky MM Yakushiji E Ichi I Westerterp M et al July 2016 TTC39B deficiency stabilizes LXR reducing both atherosclerosis and steatohepatitis Nature 535 7611 303 7 Bibcode 2016Natur 535 303H doi 10 1038 nature18628 PMC 4947007 PMID 27383786 Walter K Min JL Huang J Crooks L Memari Y McCarthy S et al October 2015 The UK10K project identifies rare variants in health and disease Nature 526 7571 82 90 Bibcode 2015Natur 526 82T doi 10 1038 nature14962 PMC 4773891 PMID 26367797 Rose Hellekant TA Schroeder MD Brockman JL Zhdankin O Bolstad R Chen KS et al August 2007 Estrogen receptor positive mammary tumorigenesis in TGFalpha transgenic mice progresses with progesterone receptor loss Oncogene 26 36 5238 46 doi 10 1038 sj onc 1210340 PMC 2587149 PMID 17334393 Crosby J Peloso GM Auer PL Crosslin DR Stitziel NO Lange LA et al July 2014 Loss of function mutations in APOC3 triglycerides and coronary disease The New England Journal of Medicine 371 1 22 31 doi 10 1056 NEJMoa1307095 PMC 4180269 PMID 24941081 Jorgensen AB Frikke Schmidt R Nordestgaard BG Tybjaerg Hansen A July 2014 Loss of function mutations in APOC3 and risk of ischemic vascular disease The New England Journal of Medicine 371 1 32 41 doi 10 1056 NEJMoa1308027 PMID 24941082 S2CID 26995834 Shuldiner AR Pollin TI August 2010 Genomics Variations in blood lipids Nature 466 7307 703 4 Bibcode 2010Natur 466 703S doi 10 1038 466703a PMID 20686562 S2CID 205057802 Teslovich TM Musunuru K Smith AV Edmondson AC Stylianou IM Koseki M et al August 2010 Biological clinical and population relevance of 95 loci for blood lipids Nature 466 7307 707 13 Bibcode 2010Natur 466 707T doi 10 1038 nature09270 PMC 3039276 PMID 20686565 Mega JL Stitziel NO Smith JG Chasman DI Caulfield MJ Devlin JJ et al June 2015 Genetic risk coronary heart disease events and the clinical benefit of statin therapy an analysis of primary and secondary prevention trials Lancet 385 9984 2264 71 doi 10 1016 S0140 6736 14 61730 X PMC 4608367 PMID 25748612 Further reading editBrown MS Goldstein JL July 1979 Receptor mediated endocytosis insights from the lipoprotein receptor system Proceedings of the National Academy of Sciences of the United States of America 76 7 3330 7 Bibcode 1979PNAS 76 3330B doi 10 1073 pnas 76 7 3330 PMC 383819 PMID 226968 Hobbs HH Brown MS Goldstein JL 1993 Molecular genetics of the LDL receptor gene in familial hypercholesterolemia Human Mutation 1 6 445 66 doi 10 1002 humu 1380010602 PMID 1301956 S2CID 5756814 Fogelman AM Van Lenten BJ Warden C Haberland ME Edwards PA 1989 Macrophage lipoprotein receptors Journal of Cell Science Supplement 9 135 49 doi 10 1242 jcs 1988 supplement 9 7 PMID 2855802 Barrett PH Watts GF March 2002 Shifting the LDL receptor paradigm in familial hypercholesterolemia novel insights from recent kinetic studies of apolipoprotein B 100 metabolism Atherosclerosis Supplements 2 3 1 4 doi 10 1016 S1567 5688 01 00012 5 PMID 11923121 May P Bock HH Herz J April 2003 Integration of endocytosis and signal transduction by lipoprotein receptors Science s STKE 2003 176 PE12 doi 10 1126 stke 2003 176 pe12 PMID 12671190 S2CID 24468290 Gent J Braakman I October 2004 Low density lipoprotein receptor structure and folding Cellular and Molecular Life Sciences 61 19 20 2461 70 doi 10 1007 s00018 004 4090 3 PMID 15526154 S2CID 21235282 External links editDescription of LDL receptor pathway at the Brown Goldstein Laboratory webpage LDL Receptor at the U S National Library of Medicine Medical Subject Headings MeSH Retrieved from https en wikipedia org w index php title LDL receptor amp oldid 1217075175, wikipedia, wiki, book, books, library,

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