Effect of caspase cleavage-site phosphorylation on proteolysis.
Caspases are important mediators of apoptotic cell death. Several cellular protein substrates of caspases contain potential phosphorylation site(s) at the cleavage-site region, and some of these sites have been verified to be phosphorylated. Since phosphorylation may affect substantially the substrate susceptibility towards proteolysis, phosphorylated, non-phosphorylated and substituted oligopeptides representing such cleavage sites were studied as substrates of apoptotic caspases 3, 7 and 8. Peptides containing phosphorylated serine residues at P4 and P1' positions were found to be substantially less susceptible towards proteolysis as compared with the serine-containing analogues, while phosphoserine at P3 did not have a substantial effect. P1 serine as well as P1-phosphorylated, serine-containing analogues of an oligopeptide representing the poly(ADP-ribose) polymerase cleavage site of caspase-3 were not hydrolysed by any of these enzymes, whereas the P1 aspartate-containing peptides were efficiently hydrolysed. These findings were interpreted with the aid of molecular modelling. Our results suggest that cleavage-site phosphorylation in certain positions could be disadvantageous or detrimental with respect to cleavability by caspases. Cleavage-site phosphorylation may therefore provide a regulatory mechanism to protect substrates from caspase-mediated degradation.
Tözsér
József
J
Department of Biochemistry and Molecular Biology, Faculty of Medicine, Debrecen University, H-4012 Debrecen, Hungary. tozser@indi.biochem.dote.hu
Bagossi
Péter
P
Zahuczky
Gábor
G
Specht
Suzanne I
SI
Majerova
Eva
E
Copeland
Terry D
TD
D001224:Aspartic Acid / Q000378:metabolism; D053148:Caspase 3; D053179:Caspase 7; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008958:Models, Molecular; D010766:Phosphorylation; D012694:Serine / Q000378:metabolism; D013379:Substrate Specificity
D001224:Aspartic Acid; D012694:Serine; C505407:CASP3 protein, human; C505520:CASP7 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053179:Caspase 7; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases