Villevalois-Cam Laurence, Rescan Claude, Gilot David, Ezan Frédéric, Loyer Pascal, Desbuquois Bernard, Guguen-Guillouzo Christiane, Baffet Georges
INSERM U522, Unité de Recherches Hépatologiques, IFR 97, Hôpital Pontchaillou, 35033 Rennes, France.
J Hepatol. 2003 Feb;38(2):156-63. doi: 10.1016/s0168-8278(02)00378-1.
BACKGROUND/AIMS: The cation-independent mannose 6-phosphate receptor (CIMPR) is overexpressed in hepatocytes during liver regeneration and has been implicated in the maturation of latent pro-transforming growth factor beta (TGFbeta). In this study, we have: (1) kinetically characterized the changes in CIMPR expression in regenerating liver and cultured proliferating hepatocytes; and (2) assessed the contribution of hepatocyte via the CIMPR to latent pro-TGFbeta activation.
The expression of CIMPR protein and mRNA in livers collected after partial hepatectomy and hepatocyte primary cultures was analyzed by Western and Northern blotting. Activity of latent pro-TGFbeta was assessed by inhibition of [3H] methylthymidine incorporation into DNA.
The expression of the CIMPR protein and/or mRNA progressively increased after 8 h in regenerating liver and 42-46 h in cultured hepatocytes, prior to the onset of DNA replication. Both mature TGFbeta and latent pro-TGFbeta inhibited epidermal growth factor-stimulated DNA synthesis in hepatocytes in a dose-dependent manner. The effect of latent pro-TGFbeta was reversed by two ligands of the CIMPR: beta-galactosidase, a mannose 6-phosphate containing protein, and a CIMPR antibody.
(1) The induction of the CIMPR gene during liver regeneration and hepatocyte culture occurs in mid G1 phase; and (2) the CIMPR mediates latent proTGFbeta activation and thus may act, by targeting TGFbeta to hepatocytes, as a negative regulator of hepatocyte growth.
背景/目的：非阳离子依赖性甘露糖6-磷酸受体（CIMPR）在肝再生过程中于肝细胞中过度表达，并与潜在的前转化生长因子β（TGFβ）的成熟有关。在本研究中，我们：（1）从动力学角度表征再生肝和培养的增殖肝细胞中CIMPR表达的变化；（2）评估肝细胞通过CIMPR对潜在前TGFβ激活的作用。
通过蛋白质免疫印迹法和Northern印迹法分析部分肝切除术后收集的肝脏及原代培养肝细胞中CIMPR蛋白和mRNA的表达。通过抑制[3H]甲基胸苷掺入DNA来评估潜在前TGFβ的活性。
在再生肝中，8小时后以及在培养的肝细胞中DNA复制开始前42 - 46小时，CIMPR蛋白和/或mRNA的表达逐渐增加。成熟TGFβ和潜在前TGFβ均以剂量依赖性方式抑制肝细胞中表皮生长因子刺激的DNA合成。CIMPR的两种配体可逆转潜在前TGFβ的作用：含甘露糖6-磷酸的蛋白质β-半乳糖苷酶和CIMPR抗体。
（1）肝再生和肝细胞培养过程中CIMPR基因的诱导发生在G1期中期；（2）CIMPR介导潜在前TGFβ的激活，因此可能通过将TGFβ靶向肝细胞而作为肝细胞生长的负调节因子发挥作用。
