Bax inhibitor 1, a modulator of calcium homeostasis, confers affective resilience

Abstract

The endoplasmic reticulum (ER) is a critical site for intracellular calcium storage as well as protein synthesis, folding, and trafficking. Disruption of these processes is gaining support for contributing to heritable vulnerability of certain diseases. Here, we investigated Bax inhibitor 1 (BI-1), an anti-apoptotic protein that primarily resides in the ER and associates with B-cell lymphoma 2 (Bcl-2) and Bcl-XL, as an affective resiliency factor through its modulation of calcium homeostasis. We found that transgenic (TG) mice with BI-1 reinforced expression, via the neuronal specific enolase promoter, showed protection against the learned helplessness (LH) paradigm, an animal model to test stress coping. TG mice were also protected against anhedonia following both serotonin and catecholamine depletion as measured in two different models, the female urine sniffing test and the saccharine preference test. In addition, we used primary mouse cortical cultures to explore the ability of BI-1 to influence calcium homeostasis under basal conditions and also following challenge with thapsigargin (THPS), an inhibitor of sarco/endoplasmic reticulum Ca2+ ATPase (SERCA) that disrupts calcium homeostasis. TG neurons showed decreased basal cytosolic calcium levels and decreased Ca2+ cytosolic accumulation following challenge with THPS as compared to WT neuronal cultures. Together, these data suggest that BI-1, through its actions on calcium homeostasis, may confer affective resiliency in multiple animal models of depression and anhedonia.