Lin Fang-Tsyr, Lai Yun-Ju, Makarova Natalia, Tigyi Gabor, Lin Weei-Chin
Department of Cell Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
J Biol Chem. 2007 Dec 28;282(52):37759-69. doi: 10.1074/jbc.M705025200. Epub 2007 Oct 26.
Lysophosphatidic acid (LPA) promotes cell survival through the activation of G protein-coupled LPA receptors. However, whether different LPA receptors activate distinct anti-apoptotic signaling pathways is not yet clear. Here we report a novel mechanism by which the LPA(2) receptor targets the proapoptotic Siva-1 protein for LPA-dependent degradation, thereby attenuating Siva-1 function in DNA damage response. The carboxyl-terminal tail of the LPA(2) receptor, but not LPA(1) or LPA(3) receptor, specifically associates with the carboxyl cysteine-rich domain of Siva-1. Prolonged LPA stimulation promotes the association of Siva-1 with the LPA(2) receptor and targets both proteins for ubiquitination and degradation. As a result, adriamycin-induced Siva-1 protein stabilization is attenuated by LPA in an LPA(2)-dependent manner, and the function of Siva-1 in promoting DNA damage-induced apoptosis is inhibited by LPA pretreatment. Consistent with this result, inhibition of the LPA(2) receptor expression increases Siva-1 protein levels and augments adriamycin-induced caspase-3 cleavage and apoptosis. Together, these findings reveal a critical and specific role for the LPA(2) receptor through which LPA directly inactivates a critical component of the death machinery to promote cell survival.
溶血磷脂酸(LPA)通过激活G蛋白偶联的LPA受体促进细胞存活。然而,不同的LPA受体是否激活不同的抗凋亡信号通路尚不清楚。在此,我们报告一种新机制,即LPA(2)受体将促凋亡蛋白Siva-1靶向进行LPA依赖的降解,从而在DNA损伤反应中减弱Siva-1的功能。LPA(2)受体的羧基末端尾巴,而非LPA(1)或LPA(3)受体,特异性地与Siva-1富含半胱氨酸的羧基结构域结合。长时间的LPA刺激促进Siva-1与LPA(2)受体的结合,并使这两种蛋白都靶向泛素化和降解。结果,阿霉素诱导的Siva-1蛋白稳定化被LPA以LPA(2)依赖的方式减弱,并且LPA预处理抑制了Siva-1在促进DNA损伤诱导的凋亡中的功能。与该结果一致,抑制LPA(2)受体表达会增加Siva-1蛋白水平,并增强阿霉素诱导的caspase-3切割和凋亡。总之,这些发现揭示了LPA(2)受体的关键且特定的作用,通过该作用LPA直接使死亡机制的关键组分失活以促进细胞存活。