Cleavage and nuclear translocation of the caspase 3 substrate Rho GDP-dissociation inhibitor, D4-GDI, during apoptosis

While investigating endonucleases potentially involved in apoptosis, an ant isera was raised to bovine deoxyribonuclease II, but it recognized a smalle r protein of 26 kDa protein in a variety of cell lines. The 26 kDa protein underwent proteolytic cleavage to 22 kDa concomitantly with DNA digestion i n cells induced to undergo apoptosis, Sequencing of the 26 kDa protein iden tified it as the Rho GDP-dissociation inhibitor D4-GDI, Zinc, okadaic acid, calyculin A, cantharidin, and the caspase inhibitor z-VAD-fmk, all prevent ed the cleavage of D4-GDI, DNA digestion, and apoptosis. The 26 kDa protein resided in the cytoplasm of undamaged cells, whereas following cleavage, t he 22 kDa form translocated to the nucleus, Human D4-GDI, and D4-GDI mutate d at the caspase 1 or caspase 3 sites, were expressed in Chinese hamster ov ary cells which show no detectable endogenous D4-GDI, Mutation at the caspa se 3 site prevented D4-GDI cleavage but did not inhibit apoptosis induced b y staurosporine. The cleavage of D4-GDI could lead to activation of Jun N-t erminal kinase which has been implicated as an upstream regulator of apopto sis in some systems. However, the results show that the cleavage of D4-GDI and translocation to the nucleus do not impact on the demise of the cell.