Proteolytic activation of PKN by caspase-3 or related protease during apoptosis

Abstract

PKN, a fatty acid-and Rho-activated serine͞ threonine kinase having a catalytic domain highly homologous to protein kinase C (PKC), was cleaved at specific sites in apoptotic Jurkat and U937 cells on Fas ligation and treatment with staurosporin or etoposide, respectively. The cleavage of PKN occurred with a time course similar to that of PKC␦, a known caspase substrate. This proteolysis was inhibited by a caspase inhibitor, acetyl-Asp-Glu-Val-Asp-aldehyde. The cleavage fragments were generated in vitro from PKN by treatment with recombinant caspase-3. Site-directed mutagenesis of specific aspartate residues prevented the appearance of these fragments. These results indicate that PKN is cleaved by caspase-3 or related protease during apoptosis. The major proteolysis took place between the amino-terminal regulatory domain and the carboxyl-terminal catalytic domain, and it generated a constitutively active kinase fragment.

Role for RhoB and PRK in the suppression of epithelial cell transformation by farnesyltransferase inhibitors

“…This interpretation of the results is consistent with the evidence that FTI both elevates and relocalizes RhoB in cells (Lebowitz et al, 1995). Although PRK2 has been reported to be cleaved and activated by caspases during apoptosis (Cryns et al, 1997;Takahashi et al, 1998), we did not observe this event. A link between PRK and FTIinduced apoptosis is potentially interesting based on reports of the ability of PRK to complex with RhoB and the Akt-regulatory enzyme PDK1 in certain epithelial and endothelial cells (Balendran et al, 1999;Flynn et al, 2000) (L. Benjamin, pers.…”

Transformation-selective apoptotic program triggered by farnesyltransferase inhibitors requires Bin1

“…comm.). In the endosomal compartment, RhoB regulates intracellular receptor trafficking through interactions with its effector kinase PRK (Mellor et al, 1998;Gampel et al, 1999), which has also been implicated in apoptosis (Cryns et al, 1997;Takahashi et al, 1998;Koh et al, 2000). Given the possibility of an effector role for Bin1 in the FTI cell suicide program, it is tempting to speculate that Bin1 may be regulated or modified at some level by Rho signals that are actinbased but directed to or from the nucleus.…”

Rubella virus-induced cytopathic effect in vitro is caused by apoptosis.

“…These substances lead to apoptosis by different mechanisms. Staurosporine is a potent protein kinase C inhibitor that rapidly induces disruption of actin filaments (Takahashi et al, 1998). Camptothecin inhibits topoisomerase I (Cotter et al, 1992) and hydrogen peroxide alters several cellular events at subtoxic concentrations, including Ca# + signalling, protein phosphorylation and cytochrome c release from mitochondria (Suzuki et al, 1997).…”