Proteome analysis of phosphorylation signaling pathways involved in maxillofacial development

p38 MAP激酶通路是一条磷酸化的细胞内信号转导通路，参与细胞发育和分化过程中细胞凋亡的调控。我们已经建立了一个细胞培养系统，其中PC 12细胞的神经元分化是通过表达组成型活性ASK 1（p38途径的激活剂）来选择性和组成性激活p38 MAP激酶来诱导的。在这里，我们已经确定了癌蛋白18（Op 18）/stathmin作为p38级联反应的一个新的潜在目标。通过双向电泳，发现磷酸化的Op 18/stathmin增加后，在PC 12细胞中的组成型活性的ASK 1的表达。经SB 203580处理后，Op 18/stathmin磷酸化的ASK 1依赖性增加减弱，表明p38α和/或p38β有助于Op 18/stathmin的磷酸化。一致地，我们发现，所有四种异构体的p38直接磷酸化Op 18/stathmin主要在丝氨酸25在体外。结合定量RT-PCR数据表明p38α是PC 12细胞中主要表达的亚型，在这些细胞中，ASK 1诱导的Op 18/stathmin磷酸化似乎主要通过p38α介导。鉴于Op 18/stathmin的微管去稳定活性受其磷酸化调节，ASK 1-p38级联可能通过Op 18/stathmin调节微管动力学。

p38 MAP kinase pathway is an intracellular signal transduction pathway using a phosphorylation relay and is involved in the regulation of apoptosis during development and differentiation. We have established a cell culture system, in which neuronal differentiation of PC12 cells is induced by the selective and constitutive activation of p38 MAP kinase through the expression of constitutively active ASK1, an activator of the p38 pathway. Here we have identified oncoprotein 18 (Op18)/stathmin as a novel potential target of the p38 cascade. By two-dimensional electrophoresis, phosphorylation of Op18/stathmin was found to be increased upon the expression of constitutively active ASK1 in PC12 cells. The ASK1-dependent increase in the phosphorylation of Op18/stathmin was attenuated by the treatment with SB203580, suggesting that p38α and/or p38β contribute to the phosphorylation of Op18/stathmin. Consistently, we found that all four isoforms of p38 directly phosphorylated Op18/stathmin primarily at serine 25 in vitro. Taken together with the quantitative RT-PCR data indicating that p38α was the dominantly expressed isoform in PC12 cells, ASK1-induced phosphorylation of Op18/stathmin appears to be mediated mainly through p38α in these cells. Given that the microtubule-destabilizing activity of Op18/stathmin is regulated by its phosphorylation, the ASK1-p38 cascade may regulate microtubule dynamics through Op18/stathmin.