Hernandez R M, Wescott G G, Mayhew M W, McJilton M A, Terrian D M
Department of Anatomy and Cell Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina 27858, USA.
J Cell Biochem. 2001;83(4):532-46. doi: 10.1002/jcb.1246.
Protein kinase C-epsilon coordinately regulates changes in cell growth and shape. Cells overproducing protein kinase C-epsilon spontaneously acquire a polarized morphology and extend long cellular membrane protrusions that are reminiscent of the morphology observed in ras-transformed fibroblasts. Here we report that the regulatory C1 domain contains an actin binding hexapeptide motif that is essential for the morphogenic effects of protein kinase C-epsilon in cultured NIH3T3 murine fibroblasts. The extension of elongate processes by protein kinase C-epsilon transformed fibroblasts appeared to be driven by a kinase-independent mechanism that required organized networks of both actin and microtubules. Flow cytometry of phalloidin-stained cells demonstrated that protein kinase C-epsilon significantly increased the cellular content of polymerized actin in NIH3T3 cells. Studies with a cell-free system suggest that protein kinase C-epsilon inhibits the in vitro disassembly of actin filaments, is capable of desequestering actin monomers from physiologically relevant concentrations of thymosin beta4, and increases the rate of actin filament elongation by decreasing the critical concentration of actin. Based on these and other observations, it is proposed that protein kinase C-epsilon may function as a terminal downstream effector in at least one of the signaling pathways that mitogens engage to initiate outgrowth of cellular protrusions.
蛋白激酶C-ε协同调节细胞生长和形态的变化。过量表达蛋白激酶C-ε的细胞会自发获得极化形态，并伸出长长的细胞膜突起，这让人联想到在ras转化的成纤维细胞中观察到的形态。在此我们报告，调节性C1结构域包含一个肌动蛋白结合六肽基序，该基序对于蛋白激酶C-ε在培养的NIH3T3小鼠成纤维细胞中的形态发生作用至关重要。蛋白激酶C-ε转化的成纤维细胞中细长突起的延伸似乎是由一种不依赖激酶的机制驱动的，该机制需要肌动蛋白和微管的有组织网络。用鬼笔环肽染色的细胞进行流式细胞术分析表明，蛋白激酶C-ε显著增加了NIH3T3细胞中聚合肌动蛋白的细胞含量。无细胞系统研究表明，蛋白激酶C-ε抑制肌动蛋白丝的体外解聚，能够从生理相关浓度的胸腺素β4中释放肌动蛋白单体，并通过降低肌动蛋白的临界浓度来增加肌动蛋白丝的伸长率。基于这些及其他观察结果，有人提出蛋白激酶C-ε可能在有丝分裂原引发细胞突起生长的至少一条信号通路中作为终末下游效应物发挥作用。
