Activation and substrate specificity of caspase-14.
Caspase-14 is a developmentally regulated and tissue restricted member of the caspase family present in mammals. It is mainly found in epidermal keratinocytes and has been hypothesized to be involved in a tissue-specific form of cell senescence, leading to the differentiation of keratinocytes that form the cornified cell layer. However, the substrate specificity, activation mechanism, and function of this caspase have yet to be revealed. We report that caspase-14, in contrast to other caspases, is not produced in active form following expression in Escherichia coli but can be activated by high concentrations of kosmotropic salts. Moreover, proteolytic cleavage is also required since the kosmotropic salts were only effective on the cleaved enzyme. We propose that caspase-14 requires proteolytic cleavage within the catalytic domain, followed by dimerization and ordering of mobile active site loops, to generate a competent enzyme. In the presence of kosmotropic salt, we were able to determine the substrate specificities of mouse and human caspase-14. Surprisingly, the substrate preferences for the human and mouse enzyme are dissimilar. The results obtained with human caspase-14 classify this enzyme as a cytokine activator, but the mouse enzyme shows preferences similar to apical apoptotic caspases.
The Program in Apoptosis and Cell Death Research, The Burnham Institute, 10901 North Torrey Pines Road, La Jolla, California 92037, USA.
Jowita
J
Mikolajczyk
Fiona L
FL
Scott
Stan
S
Krajewski
Daniel P
DP
Sutherlin
Guy S
GS
Salvesen
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D001665:Binding Sites; D053456:Caspase 14; D020169:Caspases / Q000378:metabolism*; D002478:Cells, Cultured / Q000201:enzymology*; D019281:Dimerization; D004789:Enzyme Activation / Q000502:physiology*; D004926:Escherichia coli / Q000201:enzymology; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D011994:Recombinant Proteins / Q000302:isolation & purification / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D011994:Recombinant Proteins; C506446:CASP14 protein, human; C506449:Casp14 protein, mouse; D053456:Caspase 14; D020169:Caspases