Molecular Characterization of the Proapoptotic Protein Bax

Bax is a proapoptotic member of the Bcl-2 family. Members of this family can promote either cell survival, as in the case of Bcl-2 and Bcl-X_L , or cell death, as in the case of Bax and Bak. Bax was first identified as a Bcl-2 binding partner by immunoprecipitation (1 ). Subsequently it was shown that overexpression of Bax can accelerate cell death in response to various apoptosis stimuli (2 ). Physiologically, Bax plays an important role in neuronal development and spermatogenesis. Animals that are deficient in Bax have increased number of neurons and the males are known to be sterile (3 ,4 ) Under pathological conditions such as cerebral and cardiac ischemia, upregulation of Bax has been reported in the afflicted area of the tissues, implicating the participation of this protein in promoting neuronal and cardiomyocytic cell death (5 –7 ). In certain cases of human colorectal cancer, mutations were found in the gene encoding Bax, suggesting that inactivation of Bax promotes tumorigenesis by enabling the tumor cells to be less susceptible to cell death (8 ).