Generation and Characterization of Smac/DIABLO-Deficient Mice

Abstract

The mitochondrial proapoptotic protein Smac/DIABLO has recently been shown to potentiate apoptosis by counteracting the antiapoptotic function of the inhibitor of apoptosis proteins (IAPs). In response to apoptotic stimuli, Smac is released into the cytosol and promotes caspase activation by binding to IAPs, thereby blocking their function. These observations have suggested that Smac is a new regulator of apoptosis. To better understand the physiological function of Smac in normal cells, we generated Smac-deficient (Smac ؊/؊ ) mice by using homologous recombination in embryonic stem (ES) cells. Smac ؊/؊ mice were viable, grew, and matured normally and did not show any histological abnormalities. Although the cleavage in vitro of procaspase-3 was inhibited in lysates of Smac ؊/؊ cells, all types of cultured Smac ؊/؊ cells tested responded normally to all apoptotic stimuli applied. There were also no detectable differences in Fas-mediated apoptosis in the liver in vivo. Our data strongly suggest the existence of a redundant molecule or molecules capable of compensating for a loss of Smac function.

Variations in the protein level of Omi/HtrA2 in the heart of aged rats may contribute to the increased susceptibility of cardiomyocytes to ischemia/reperfusion injury and cell death

“…Although Omi/HtrA2 and Smac/DIABLO both seem to target XIAP, an increasing evidence suggests that Omi/HtrA2 may play a unique role in apoptosis. Several different Smac/DIA-BLO-deficient cells respond normally to various apoptotic stimuli, suggesting the existence of a redundant molecule or molecules compensating for a loss of Smac/DIABLO function (Okada et al 2002). However, overexpression of Omi/HtrA2 sensitizes cells to apoptosis, and its removal by RNA interference reduces cell death (Martins et al 2002).…”

Genetic variance modifies apoptosis susceptibility in mature oocytes via alterations in DNA repair capacity and mitochondrial ultrastructure

“…To this end, microinjection of recombinant Smac/ DIABLO increased apoptosis in B6C3F1 oocytes, and coinjecting cytochrome c synergistically enhanced this effect. Although Smac/DIABLO-deficient mice were reported to have no phenotype, 13 outcrossing these mutants onto a FVB background has now uncovered a central role for this gene product in executing apoptosis in the germ line of animals with disrupted mitochondrial integrity.…”

Caspase function in programmed cell death

“…The smac KO mice develop normally and smac-deficient cells are sensitive to apoptosis induced via both intrinsic and extrinsic pathways. 137 HtrA2 KO animals die around 30 days after birth owing to a neurodegenerative disorder, but cells derived from these animals fail to show any resistance to apoptosis. 138 Combined deficiency of HtrA2 and SMAC leads to a phenotype similar to HtrA2 deficiency alone, suggesting that these two proteins are not compensating for each other.…”