P 163 - Bcl-2 modulates ER/SR calcium uptake by interaction with SERCA and heat shock proteins

Abstract

Bcl-2 is an anti-apoptotic protein, which is involved in the interaction with multiple proteins at various cellular locations, including mitochondria and the ER. We show here, that Bcl-2 interacts efficiently with various isoforms of the sarco/endoplasmic reticulum Ca-ATPase (SERCA), including SERCA1, SERCA2 and SERCA3, which leads to SERCA inactivation, conformational changes, and translocation of SERCA between specific membrane microdomains. These functional effects of Bcl-2 are demonstrated both in vitro, and in cells overexpressing Bcl-2 and SERCA. Co-immunoprecipitation experiments confirm the interaction of Bcl-2 and SERCA in vitro and in cell culture. Amino acids critical for the functional interaction of Bcl-2 with SERCA have been identified ny mutagenesis. One example is the mutation of Gly145 to Glu145, which reduces the ability of Bcl-2 to inactivate SERCA. This mutation had previously been shown by others to lower the anti-apoptotic activity of Bcl-2, providing an interesting parallel between the anti-apoptotic activity of Bcl-2 and its potency to inactivate SERCA. Heat shock proteins prevent the Bcl-2-induced inactivation of SERCA, even when heat shock proteins carry oxidative post-translational modifications such 3-nitrotyrosine and/or 4-hydroxynonenal adducts (i.e., modifications accumulated under conditions of oxidative stress).