Wen L P, Madani K, Martin G A, Rosen G D
Department of Pulmonary and Critical Care Medicine, Stanford University, Stanford, California 94305-5236, USA.
Cell Death Differ. 1998 Sep;5(9):729-34. doi: 10.1038/sj.cdd.4400409.
p120-ras GTPase-activating protein (rasGAP) associates with Ras and negatively regulates Ras signaling by stimulating the intrinsic rate of Ras GTPase activity. rasGAP also associates with other cellular signaling proteins which suggest that rasGAP may play a role in coordinating other signal transduction pathways. Disruption of rasGAP in vivo results in extensive apoptosis. Fas-mediated apoptosis results in the activation of caspases that cleave cellular substrates which are important for maintaining cytoplasmic and nuclear integrity. We show here that rasGAP is proteolytically cleaved by caspases early in Fas-induced apoptosis of Jurkat cells. rasGAP was also cleaved by DNA-damaging chemotherapeutic agents and TNF-related apoptosis inducing ligand (TRAIL), also known as Apo2L. Based on the size of the products generated by cleavage of deletion mutants of rasGAP we predict that cleavage of rasGAP occurs in the hydrophobic region and between the SH2(2) and ras-p21 interacting domain which would leave an intact ras-p21 interacting domain. Interestingly, cleavage of rasGAP in vitro enhanced rasGAP hydrolysis activity. Our results demonstrate that diverse apoptotic stimuli cause caspase-mediated cleavage of rasGAP early in apoptosis.
p120-ras GTP酶激活蛋白（rasGAP）与Ras结合，并通过刺激Ras GTP酶活性的内在速率来负向调节Ras信号传导。rasGAP还与其他细胞信号蛋白结合，这表明rasGAP可能在协调其他信号转导途径中发挥作用。体内rasGAP的破坏会导致广泛的细胞凋亡。Fas介导的细胞凋亡导致半胱天冬酶的激活，这些酶会切割对维持细胞质和细胞核完整性很重要的细胞底物。我们在此表明，在Jurkat细胞Fas诱导的细胞凋亡早期，rasGAP会被半胱天冬酶进行蛋白水解切割。rasGAP也会被DNA损伤化疗药物和肿瘤坏死因子相关凋亡诱导配体（TRAIL，也称为Apo2L）切割。根据rasGAP缺失突变体切割产生的产物大小，我们预测rasGAP的切割发生在疏水区域以及SH2(2)和ras-p21相互作用结构域之间，这将留下完整的ras-p21相互作用结构域。有趣的是，体外切割rasGAP会增强rasGAP的水解活性。我们的结果表明，多种凋亡刺激在细胞凋亡早期会导致半胱天冬酶介导的rasGAP切割。
