Alix, a novel mouse protein undergoing calcium-dependent interaction with the apoptosis-linked-gene 2 (ALG-2) protein

ALG-2 is a EF hand calcium binding protein with sequence homologies to calmodulin. Vito et al have shown that ALG-2 expression is required for apoptosis following a number of death stimuli,(1) although nothing is known about the effecters which underlie ALG-2 function. Here we have used ALG-2 as bait in a yeast two hybrid screen of a mouse brain cDNA library. We found that ALG-2 binds to itself and to a novel protein that we call ALG-2 interacting protein X Alix. Using coimmunoprecipitation experiments, we confirmed ALG-2/ALG-2 binding and demonstrated that this interaction is calcium independent. ALG-2/Alix interaction was also validated by co-immunoprecipitation, but in this case, the binding was found to be strictly calcium dependent, Alix seems highly conserved throughout evolution since it shows significant homologies to a putative C. elegans protein (YNK-1) and to proteins of A. nidulans (PalA) and S, cerevisiae (BRO1). Alix is a potential regulator or downstream effector of ALG-2 action.