Singh Ugra S, Pan Jing, Kao Yu-Lin, Joshi Suchitra, Young Keri L, Baker Kenneth M
Division of Molecular Cardiology, Cardiovascular Research Institute, The Texas A&M University System Health Science Center, College of Medicine, Temple, Texas 76504, USA.
J Biol Chem. 2003 Jan 3;278(1):391-9. doi: 10.1074/jbc.M206361200. Epub 2002 Oct 24.
All-trans-retinoic acid (RA) plays a crucial role in survival and differentiation of neurons. For elucidating signaling mechanisms involved in RA-induced neuronal differentiation, we have selected SH-SY5Y cells, which are an established in vitro cell model for studying RA signaling. Here we report that RA-induced neuronal differentiation of SH-SY5Y cells is coupled with increased expression/activation of TGase and in vivo transamidation and activation of RhoA. In addition, RA promotes formation of stress fibers and focal adhesion complexes, and activation of ERK1/2, JNK1, and p38alpha/beta/gamma MAP kinases. Using C-3 exoenzyme (RhoA inhibitor) or monodansylcadaverine (TGase inhibitor), we show that transamidated RhoA regulates cytoskeletal rearrangement and activation of ERK1/2 and p38gamma MAP kinases. Further, by using stable SH-SY5Y cell lines (overexpressing wild-type, C277S mutant, and antisense TGase), we demonstrate that transglutaminase activity is required for activation of RhoA, ERK1/2, JNK1, and p38gamma MAP kinases. Activated MAP kinases differentially regulate RA-induced neurite outgrowth and neuronal marker expression. The results of our studies suggest a novel mechanism of RA signaling, which involves activation of TGase and transamidation of RhoA. RA-induced activation of TGase is proposed to induce multiple signaling pathways that regulate neuronal differentiation.
全反式维甲酸（RA）在神经元的存活和分化中起着关键作用。为了阐明RA诱导神经元分化所涉及的信号机制，我们选择了SH-SY5Y细胞，它是一种用于研究RA信号的成熟体外细胞模型。在此我们报告，RA诱导的SH-SY5Y细胞神经元分化与转谷氨酰胺酶（TGase）表达/激活增加以及RhoA的体内转酰胺化和激活有关。此外，RA促进应力纤维和粘着斑复合物的形成，以及ERK1/2、JNK1和p38α/β/γ丝裂原活化蛋白激酶（MAP激酶）的激活。使用C-3外切酶（RhoA抑制剂）或单丹磺酰尸胺（TGase抑制剂），我们发现转酰胺化的RhoA调节细胞骨架重排以及ERK1/2和p38γ MAP激酶的激活。此外，通过使用稳定的SH-SY5Y细胞系（过表达野生型、C277S突变体和反义TGase），我们证明转谷氨酰胺酶活性是激活RhoA、ERK1/2、JNK1和p38γ MAP激酶所必需的。激活的MAP激酶对RA诱导的神经突生长和神经元标志物表达有不同的调节作用。我们的研究结果提示了一种新的RA信号机制，该机制涉及TGase的激活和RhoA的转酰胺化。RA诱导的TGase激活被认为可诱导多种调节神经元分化的信号通路。
