title: Chemical chaperone treatment reduces intracellular accumulation of mutant collagen IV and ameliorates the cellular phenotype of a COL4A2 mutation that causes haemorrhagic stroke.
abstract: Haemorrhagic stroke accounts for ∼20% of stroke cases and porencephaly is a clinical consequence of perinatal cerebral haemorrhaging. Here, we report the identification of a novel dominant G702D mutation in the collagen domain of COL4A2 (collagen IV alpha chain 2) in a family displaying porencephaly with reduced penetrance. COL4A2 is the obligatory protein partner of COL4A1 but in contrast to most COL4A1 mutations, the COL4A2 mutation does not lead to eye or kidney disease. Analysis of dermal biopsies from a patient and his unaffected father, who also carries the mutation, revealed that both display basement membrane (BM) defects. Intriguingly, defective collagen IV incorporation into the dermal BM was observed in the patient only and was associated with endoplasmic reticulum (ER) retention of COL4A2 in primary dermal fibroblasts. This intracellular accumulation led to ER stress, unfolded protein response activation, reduced cell proliferation and increased apoptosis. Interestingly, the absence of ER retention of COL4A2 and ER stress in cells from the unaffected father indicate that accumulation and/or clearance of mutant COL4A2 from the ER may be a critical modifier for disease development. Our analysis also revealed that mutant collagen IV is degraded via the proteasome. Importantly, treatment of patient cells with a chemical chaperone decreased intracellular COL4A2 levels, ER stress and apoptosis, demonstrating that reducing intracellular collagen accumulation can ameliorate the cellular phenotype of COL4A2 mutations. Importantly, these data highlight that manipulation of chaperone levels, intracellular collagen accumulation and ER stress are potential therapeutic options for collagen IV diseases including haemorrhagic stroke.
authors.affiliation: Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK.
authors.forename: Lydia S
authors.initials: LS
authors.lastname: Murray
authors.forename: Yinhui
authors.initials: Y
authors.lastname: Lu
authors.forename: Aislynn
authors.initials: A
authors.lastname: Taggart
authors.forename: Nicole
authors.initials: N
authors.lastname: Van Regemorter
authors.forename: Catheline
authors.initials: C
authors.lastname: Vilain
authors.forename: Marc
authors.initials: M
authors.lastname: Abramowicz
authors.forename: Karl E
authors.initials: KE
authors.lastname: Kadler
authors.forename: Tom
authors.initials: T
authors.lastname: Van Agtmael
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D001485:Basement Membrane / Q000187:drug effects / Q000503:physiopathology*; D001927:Brain Diseases / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D024141:Collagen Type IV / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects; D005260:Female; D006429:Hemiplegia / Q000188:drug therapy* / Q000235:genetics / Q000473:pathology; D006801:Humans; D020300:Intracranial Hemorrhages / Q000150:complications / Q000188:drug therapy* / Q000235:genetics; D008297:Male; D009154:Mutation; D010641:Phenotype; D010654:Phenylbutyrates / Q000494:pharmacology*; D065708:Porencephaly; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D020521:Stroke / Q000150:complications / Q000188:drug therapy* / Q000235:genetics
chemical_list: C547475:COL4A1 protein, human; C502625:COL4A2 protein, human; D024141:Collagen Type IV; D010654:Phenylbutyrates; C075773:4-phenylbutyric acid; D046988:Proteasome Endopeptidase Complex