Expression of apoptosis specific proteins (ASPs) during apoptosis and autophagy.
ASPs (apoptosis specific proteins) are a protein family with a molecular weight
betwccn 20K and 140K. Expression has been found mainly in apoptotic cells. However, some
family members have also been detected in viable cells. It has been confirmed by confocal
microscopy that these proteins are predominately located along the actin cytoskeleton vvith
particular high concentrations corresponding to a-actinin.
A gene encoding the 32K ASP component has been cloned from a human foetal liver
expression library. This 32K ASP protein (termed Apg5L; ApgS [autophagy 5. S. cerevisiae]-like,
human [h]Apg5; Apg5) is homologues to the product of the yeast Apg5 gene. In yeast.
Apg5 is essential for a novel protein conjugation system during autophagy. It is believed that
members of the ASP family (i.e. 32K ASP/Apg5L) are involved in a similar conjugation
system in mammals. This assumption is based on the observation that polyclonal antibodies
raised against ApgSL recognise a set of proteins with co-localise with members of the ASP
family detected by immunofluorescence.