Unphosphorylated MARCKS is involved in neurite initiation induced by insulin-like growth factor-I in SH-SY5Y cells
Unphosphorylated MARCKS is involved in neurite initiation induced by insulin-like growth factor-I in SH-SY5Y cells
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DOI：
10.1002/jcp.20814
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发表时间：
2006-12-01
影响因子：
5.6
通讯作者：
Sasaki, Yasuharu
中科院分区：
文献类型：
--
作者：
Shiraishi, Mitsuya;Tanabe, Atsuhiro;Sasaki, Yasuharu
肉豆蔻酰化富含丙氨酸的C激酶底物(MARCKS)被认为参与了神经细胞分化的各个方面，包括轴突的生长。然而，MARCKS磷酸化被调控的确切机制，以及MARCKS如何促进轴突生长，目前还知之甚少。在这里，我们发现用胰岛素样生长因子-1(IGF-1)处理SH-SY5Y细胞后，磷酸化Marcks(P-Marcks)水平迅速而短暂地下降到基础水平以下。磷脂酰肌醇3-激酶(PI3K)抑制剂LY294002和Wortmannin可阻断IGF-1诱导的P-Marcks下降。在用Rho依赖的激酶(ROCK)抑制剂Y27632处理的细胞中，也观察到P-Marcks的减少。此外，IGF-1还诱导了ROCK上游效应分子RhoA的瞬时失活。我们发现，在IGF-1刺激的细胞中，Marcks被移位到细胞膜上，并与F-肌动蛋白共存于板层脂膜和神经突起的顶端。最后，过表达野生型MARCKS或MARCKS的非磷酸化突变体与载体转染型细胞相比，增加了轴突细胞的数量。综上所述，这些发现表明未磷酸化的Marcks参与了轴突的形成，并强调了Marcks在肌动蛋白细胞骨架的组织中所起的重要作用。
Myristoylated alanine-rich C kinase substrate (MARCKS) has been suggested to be involved in various aspects of neuronal cell differentiation, including neurite outgrowth. However, the precise mechanisms by which MARCKS phosphorylation is regulated, and how MARCKS contributes to neurite outgrowth, are poorly understood. Here, we found that treatment of SH-SY5Y cells with insulin-like growth factor-1 (IGF-1) induced a rapid and transient decrease in the level of phosphorylated MARCKS (P-MARCKS) to below the basal level. The decrease in P-MARCKS induced by IGF-1 was blocked by pretreatment of cells with phosphoinositide 3-kinase (PI3K) inhibitors, LY294002 and wortmannin. A decrease in P-MARCKS was also observed in cells treated with a Rho-dependent kinase (ROCK) inhibitor, Y27632. Furthermore, IGF-1 induced transient inactivation of RhoA, an upstream effector of ROCK. We showed that MARCKS was translocated to the membrane and colocalized with F-actin at the lamellipodia and the tips of neurites in the cells stimulated with IGF-1. Finally, overexpression of wild-type MARCKS or an unphosphorylatable mutant of MARCKS enhanced the number of neurite-bearing cells relative to vector-transfected cells. Taken together, these findings suggest that unphosphorylated MARCKS is involved in neurite initiation, and highlight the important role played by MARCKS in organization of the actin cytoskeleton.