C. Brancolini et al., MICROFILAMENT REORGANIZATION DURING APOPTOSIS - THE ROLE OF GAS2, A POSSIBLE SUBSTRATE FOR ICE-LIKE PROTEASES, EMBO journal, 14(21), 1995, pp. 5179-5190
Gas2, a component of the microfilament system, belongs to the class of
gas genes whose expression is induced at growth arrest, After serum o
r growth factor addition to quiescent NIH 3T3 cells, Gas2 is hyperphos
phorylated and relocalized at the membrane ruffles. By overexpressing
gas2wt and a series of deletion mutants of the C-terminal region, we h
ave analysed its role in the organization of the actin cytoskeleton in
different cell lines, Overexpression of Gas2 deleted at its C-termina
l region (Delta 276-314 and Delta 236-314), but not its wild-type form
, induces dramatic changes in the actin cytoskeleton and cell morpholo
gy, These effects are not-due to interference of the deleted forms wit
h the endogenous Gas2wt function but could be ascribed to a gain of fu
nction. We demonstrate that during apoptosis the C-terminal domain of
Gas2 is removed by proteolytic cleavage, resulting in a protein that i
s similar in size to the described Delta 276-314. Moreover, by using i
n vitro mutagenesis, we also demonstrate that the proteolytic processi
ng of Gas2 during apoptosis is dependent on an aspartic acid residue a
t position 279. The evidence accumulated here could thus represent a f
irst example of a mechanism linking apoptosis with the co-ordinated mi
crofilament-dependent cell shape changes, as possibly mediated by an i
nterleukin-1 beta-converting enzyme (ICE)-like dependent proteolytic c
leavage of the Gas2 protein.