D4-GDI, a Substrate of CPP32, Is Proteolyzed during Fas-induced Apoptosis
Journal of Biological Chemistry
Apoptosis (programmed cell death) is a fundamental process for normal development of multicellular organisms, and is involved in the regulation of the immune system, normal morphogenesis, and maintenance of homeostasis. ICE/CED-3 family cysteine proteases have been implicated directly in apoptosis, but relatively few of the substrates through which their action is mediated have been identified. Here we report that D4-GDI, an abundant hematopoietic cell GDP dissociation inhibitor for the
... tor for the Ras-related Rho family GTPases, is a substrate of the apoptosis protease CPP32/Yama/Apopain. D4-GDI was rapidly truncated to a 23-kDa fragment in Jurkat cells with kinetics that parallel the onset of apoptosis following Fas cross-linking with agonistic antibody or treatment with staurosporine. Fas-and staurosporineinduced apoptosis as well as cleavage of D4-GDI were inhibited by the ICE inhibitor, YVAD-cmk. D4-GDI was cleaved in vitro by recombinant CPP32 expressed in Escherichia coli to form a 23-kDa fragment. The CPP32mediated cleavage of D4-GDI was completely inhibited by 1 M DEVD-CHO, a reported selective inhibitor of CPP32. In contrast, the ICE-selective inhibitors, YVAD-CHO or YVAD-cmk, did not inhibit CPP32-mediated D4-GDI cleavage at concentrations up to 50 M. N-terminal sequencing of the 23-kDa D4-GDI fragment demonstrated that D4-GDI was cleaved between Asp 19 and Ser 20 of the poly(ADP-ribose) polymerase-like cleavage sequence DELD 19 S. These data suggest that regulation by D4-GDI of Rho family GTPases may be disrupted during apoptosis by CPP32-mediated cleavage of the GDI protein.