Accumulation of type IV collagen in dilated ER leads to apoptosis in Hsp47-knockout mouse embryos via induction of CHOP.
Hsp47 is an endoplasmic reticulum (ER)-resident molecular chaperone that is specific for collagen. In Hsp47(-/-) mouse embryos at 9.5 days postcoitus (dpc), immunostaining indicated the absence of type IV collagen, but not of laminin and nidogen-1, in the basement membrane (BM). Electron immunomicroscopy revealed accumulation of type IV collagen in dilated ERs, but not in the BM of Hsp47(-/-) embryos, whereas it was only present in the BM in Hsp47(+/+) embryos. The BM structures stained with anti-laminin and anti-nidogen-1 antibody became disrupted in Hsp47(-/-) embryos at 10.5 dpc. Thus, in the absence of type IV collagen in the BM owing to the lack of Hsp47, the structure of the BM cannot be maintained during the dramatic morphological changes that take place around 10.5 dpc. Type IV collagen is therefore indispensable for the maintenance of BM structures during the late-stage development of mouse embryos, although not essential for the initial formation of the BM. Just before the death of Hsp47(-/-) embryos, DNA fragmentation typical of apoptosis was observed at 10.5 dpc together with significantly upregulated CHOP mRNA expression. ER stress caused by the accumulation of misfolded collagen may have induced apoptosis in Hsp47-knockout embryos through the upregulation of CHOP.
Marutani
Toshihiro
T
Department of Molecular and Cellular Biology and CREST/JST, Institute for Frontier Medical Sciences, Kyoto University, Sakyo-ku, Kyoto 606-8397, Japan.
Yamamoto
Akitsugu
A
Nagai
Naoko
N
Kubota
Hiroshi
H
Nagata
Kazuhiro
K
D000818:Animals; D017209:Apoptosis; D022762:CCAAT-Enhancer-Binding Proteins / Q000096:biosynthesis* / Q000378:metabolism; D003094:Collagen / Q000737:chemistry / Q000378:metabolism; D024141:Collagen Type IV / Q000378:metabolism*; D004247:DNA / Q000378:metabolism; D053938:DNA Fragmentation; D018076:DNA, Complementary / Q000378:metabolism; D004587:Electrophoresis, Agar Gel; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D050958:HSP47 Heat-Shock Proteins; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism*; D020287:In Situ Nick-End Labeling; D007797:Laminin / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D008822:Mice, Transgenic; D016253:Microscopy, Immunoelectron; D009154:Mutation; D017510:Protein Folding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015843:Serpins / Q000235:genetics* / Q000378:metabolism*; D013997:Time Factors; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000096:biosynthesis* / Q000378:metabolism; D015854:Up-Regulation
D022762:CCAAT-Enhancer-Binding Proteins; D024141:Collagen Type IV; D018076:DNA, Complementary; C497250:Ddit3 protein, mouse; D050958:HSP47 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D007797:Laminin; D008562:Membrane Glycoproteins; C494661:Serpinh1 protein, mouse; D015843:Serpins; D014157:Transcription Factors; C029967:nidogen; D051742:Transcription Factor CHOP; D003094:Collagen; D004247:DNA