title: Evidence for activation of the unfolded protein response in collagen IV nephropathies.
abstract: Thin-basement-membrane nephropathy (TBMN) and Alport syndrome (AS) are progressive collagen IV nephropathies caused by mutations in COL4A3/A4/A5 genes. These nephropathies invariably present with microscopic hematuria and frequently progress to proteinuria and CKD or ESRD during long-term follow-up. Nonetheless, the exact molecular mechanisms by which these mutations exert their deleterious effects on the glomerulus remain elusive. We hypothesized that defective trafficking of the COL4A3 chain causes a strong intracellular effect on the cell responsible for COL4A3 expression, the podocyte. To this end, we overexpressed normal and mutant COL4A3 chains (G1334E mutation) in human undifferentiated podocytes and tested their effects in various intracellular pathways using a microarray approach. COL4A3 overexpression in the podocyte caused chain retention in the endoplasmic reticulum (ER) that was associated with activation of unfolded protein response (UPR)-related markers of ER stress. Notably, the overexpression of normal or mutant COL4A3 chains differentially activated the UPR pathway. Similar results were observed in a novel knockin mouse carrying the Col4a3-G1332E mutation, which produced a phenotype consistent with AS, and in biopsy specimens from patients with TBMN carrying a heterozygous COL4A3-G1334E mutation. These results suggest that ER stress arising from defective localization of collagen IV chains in human podocytes contributes to the pathogenesis of TBMN and AS through activation of the UPR, a finding that may pave the way for novel therapeutic interventions for a variety of collagenopathies.
authors.affiliation: Molecular Medicine Research Center, Department of Biological Sciences, University of Cyprus, Nicosia, Cyprus;
authors.forename: Myrtani
authors.initials: M
authors.lastname: Pieri
authors.forename: Charalambos
authors.initials: C
authors.lastname: Stefanou
authors.forename: Apostolos
authors.initials: A
authors.lastname: Zaravinos
authors.forename: Kamil
authors.initials: K
authors.lastname: Erguler
authors.forename: Kostas
authors.initials: K
authors.lastname: Stylianou
authors.forename: George
authors.initials: G
authors.lastname: Lapathitis
authors.forename: Christos
authors.initials: C
authors.lastname: Karaiskos
authors.forename: Isavella
authors.initials: I
authors.lastname: Savva
authors.forename: Revekka
authors.initials: R
authors.lastname: Paraskeva
authors.forename: Harsh
authors.initials: H
authors.lastname: Dweep
authors.forename: Carsten
authors.initials: C
authors.lastname: Sticht
authors.forename: Natassa
authors.initials: N
authors.lastname: Anastasiadou
authors.forename: Ioanna
authors.initials: I
authors.lastname: Zouvani
authors.forename: Demetris
authors.initials: D
authors.lastname: Goumenos
authors.forename: Kyriakos
authors.initials: K
authors.lastname: Felekkis
authors.forename: Moin
authors.initials: M
authors.lastname: Saleem
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Voskarides
authors.forename: Norbert
authors.initials: N
authors.lastname: Gretz
authors.forename: Constantinos
authors.initials: C
authors.lastname: Deltas
mesh_terms: D000818:Animals; D001324:Autoantigens / Q000235:genetics / Q000502:physiology; D001706:Biopsy; D002478:Cells, Cultured; D024141:Collagen Type IV / Q000172:deficiency* / Q000235:genetics / Q000502:physiology; D004268:DNA-Binding Proteins / Q000378:metabolism; D004195:Disease Models, Animal; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000502:physiology*; D020869:Gene Expression Profiling; D055879:Gene Knock-In Techniques; D050533:Glomerular Basement Membrane / Q000378:metabolism* / Q000473:pathology; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics; D006579:Heterozygote; D006801:Humans; D007668:Kidney / Q000378:metabolism / Q000473:pathology; D051379:Mice; D020125:Mutation, Missense; D009394:Nephritis, Hereditary / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis; D050199:Podocytes / Q000378:metabolism* / Q000473:pathology; D017354:Point Mutation; D040081:Protein Array Analysis; D021381:Protein Transport; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology; D011993:Recombinant Fusion Proteins; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors / Q000378:metabolism; D014162:Transfection; D056811:Unfolded Protein Response / Q000502:physiology*
chemical_list: D001324:Autoantigens; C466620:COL4A4 protein, human; C478159:COL4A5 protein, human; D024141:Collagen Type IV; D004268:DNA-Binding Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; C057112:type IV collagen alpha3 chain