Cloning and characterization of newly described proteins from a fat-storing cell library : their significance in the activation of the cells.

脂肪储存细胞（FSC）转化为肌成纤维细胞，在肝纤维形成中起重要作用。我们从一个大鼠脂肪储存细胞文库中分离出两个cdna， C72和C81。C72 cDNA包含一个开放阅读框，编码468个氨基酸残基的蛋白。C72 cDNA的核苷酸序列与I型前胶原c蛋白酶增强蛋白（PCPE）基因同源。从新鲜分离的和早期传代的FSC和成纤维细胞中提取的总RNA中，通过Northern blot识别的C72 cDNA为1.7 kb mRNA。与新鲜分离的FSC相比，早期传代FSC中C72 mRNA的表达增加了3倍。在大鼠全肝、新鲜分离肝细胞、内皮细胞和库普弗细胞中均未检测到C72 mRNA。然而，在cc1_1 -肝硬化肝脏中诱导了C72 mRNA的表达。另一方面，我们发现cDNA的衍生c端包含特定于rna结合共识序列的基序，这表明PCPE具有增强子活性以外的功能。带反义寡核苷酸的PCPE下调抑制FSC中非胶原蛋白的产生以及胶原蛋白的产生。C81 cDNA包含一个开放阅读框，编码563个氨基酸残基。推导出的氨基酸序列与先前报道的蛋白质没有显著的同源性。在新分离的FSC中，C81 cDNA与2.1 kb mRNA杂交。杂交带在早期传代FSC中消失，在成纤维细胞中未检测到信号。从这些结果来看，这些cdna可以作为跟踪肝纤维化发展过程中HSC向肌成纤维细胞转化的有用工具。

Fat-storing cells (FSC) transform into myofibroblasts and play an important role in liver fibrogenesis. We isolated two cDNAs, C72 and C81, from a rat fat-storing cell library.C72 cDNA contained an open reading frame coding for a protein of 468 amino acid residues. C72 cDNA had a nucleotide sequence homologous to that of the gene for the type I procollagen C-proteinase enhancer protein (PCPE). C72 cDNA recognized by Northern blot a 1.7 kb mRNA in total RNA extracted from freshly isolated and early passaged FSC and fibroblasts. The expression of C72 mRNA was increased 3-fold in early passaged FSC as compared to freshly isolated FSC.C72 mRNA was not detected in total rat liver, freshly isolated hepatocytes, endothelial or Kupffer cells. However, the expression of C72 mRNA was induced in CC1_4-cirrhotic livers. On the other hand, we revealed that the derived C-terminus of the cDNA contains motifs specific to RNA-binding consensus sequence, suggesting that PCPE has a function other than the enhancer activity. The down-regulation of PCPE with an antisense oligonucleotide inhibited non-collagenous protein production as well as collagen production in FSC.C81 cDNA contained an open reading frame which codes 563 amino acid residues. Its deduced amino acid sequence showed no significant homology to previously reported proteins. C81 cDNA hybridized with a 2.1 kb mRNA presented in freshly isolated FSC.The hybridization band disappeared in early passaged FSC,and no signals were detected in fibroblasts.From these results, these cDNAs can be useful tools to follow the transformation of HSC to myofibroblasts during development of hepatic fibrosis.