p21-activated protein kinase gamma-PAK suppresses programmed cell death of BALB3T3 fibroblasts

In response to stress stimulants, cells activate opposing signaling pathways for cell survival and programmed cell death. p21-activated protein kinase gamma-PAK is involved in both cell survival and cell death pathways. Many stress stimulants activate gamma-PAK as a full-length enzyme and as a proteolytic fragment. Caspase-mediated proteolytic activation parallels cell death and appears to be a pro-apoptotic factor in stress-induced cell death. Here, we show that activation of full-length gamma-PAK promotes cell survival and suppresses stress-induced cell death. Expression of constitutively active gamma-PAK-T402E, which mimics activated full-length gamma-PAK, stimulates cell survival of BALB3T3 fibroblasts in response to tumor necrosis factor alpha, growth factor withdrawal, and UVC light. This stimulation of cell survival is mainly due to protection of cells from cell death rather than by stimulation of proliferation. Expression of gamma-PAK-T402E increases phosphorylation of the pro-apoptotic Bcl-2 family protein Bad and protects from cell death induced by ectopic expression of Bad. In response to tumor necrosis factor alpha, expression of gamma-PAK-T402E increases the early but reduces the late activation of ERK, JNK, and p38. Our results indicate that the ubiquitous gamma-PAK may have a crucial function in cell survival by regulating the pro-apoptotic activity of Bad and the stress-induced activation of ERK, JNK, and p38 pathways.