The Mechanisms of Hepatic Stellate Cell Activation : Possible Contribution of Type I Procollagen C-Proteinase Enhancer Protein.

点击翻译按钮获取中文摘要

Previously, we isolated type I procollagen C-proteinase enhancer (PCPE) cDNA from the library of hepatic stellate cells (HSC). The C-terminus of the deduced amino acid sequence of PCPE cDNA was shown to contain motifs specific for RNA-binding proteins. PCPE protein expression increased progressively in HSCs under an "activation" process, in which the cells are transformed to myofibroblast-like cells. PCPE protein expression was minimal in HSC following incubation with addition of an antisense oligonucleotide (AS) for PCPE mRNA to the culture medium. In these cells, the syntheses of non-collagenous protein as well as collagen were attenuated in comparison with the cells with the nonsense oligonucleotide (NS) addition. Thus, PCPE protein may contribute to the protein production in HSC through binding to RNAs.First, we studied the effect of growth factors on HSC function. PDGF was added to the culture medium of activated HSCs. Twenty-four hours later, double immunostaining of BrdU and smo … More oth muscle α actin in activated HSCs were performed. We found that HSC at the S-phase of the cell cycle after activation by culture express none or less smooth muscle α actin. Next, we found that quiescent HSCs expressed both flt-1 and KDR/flk-1. When HSCs were activated, flt-1 expression were increased compared to that in the quiescent HSCs. In contrast, KDR/flk-1 expression in the cells diminished. VEGF produced no changes in DNA and collagen syntheses by the quiescent and activated HSCs. When VEGF was added to the culture medium of activated HSCs, the expression of smooth muscle α actin was attenuated and contraction of activated HSCs was inhibited.Finally, we studied the role of PCPE protein in the metabolism of RNA in HSCs. AS or NS were added to the culture medium of activated HSCs, and total RNA was extracted from the cells serially up to 36 h. Cellular contents of total RNA were not different between the cells treated with AS and NS. When actinomycin D was added to HSCs, the amout of total RNA was decreased more rapidly in cells treated with AS than that with NS.In conclusion, PCPE protein may be involved in the stabilization of RNAs leading to contribution of protein production in HSCs. The interaction between PCPE and various growth factors should be investigated in HSCs in future. Less