Apoptosis-specific protein (ASP 45 kDa) is distinct from human Apg5, the homologue of the yeast autophagic gene apg5

We have examined whether the apoptosis-specitic protein p45ASP and human Apg5 are identical proteins. Like p45ASP, myc-hApg5 cross-reacted with a c-Jun antibody and similar to50% of myc-hApg5 was bound to a Triton X-100-insoluble fraction in HeLa cells. However, soluble myc-hApg5 was degraded during apoptosis induced by staurosporine or TNFalpha/cycloheximide whilst expression of soluble p45ASP was stabilised. Furthermore, myc-hApg5 degradation was blocked by the caspase inhibitor Boc-Asp(OMe)FMK whilst p45ASP expression was eliminated. Moreover, myc-hApg5 (similar to32 kDa) never assumed the size of p45ASP (45 kDa). It is therefore likely that p45ASP and human Apg5 are distinct proteins although they do share some common characteristics. (C) 2002 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.