Nesprin-2 contains BH3-like motifs that can promote cell death.

Abstract

BH3-only proteins are a subgroup of the pro-apoptotic Bcl-2 family proteins. They initiate apoptosis by interacting with the multidomain pro- and anti-apoptotic Bcl-2 family proteins. SYNE2 encodes multiple nesprin-2 (Nes2) isoforms of which the most abundant and the largest is the nuclear envelope protein nesprin-2 giant (Nes2G). Nes2G is a component of the nuclear envelope Linker of Nucleoskeleton and Cytoskeleton (LINC) complex that connects the nucleus and the cytoskeleton. Previously, we showed that Nes2 has pro-apoptotic activity. We now show that Nes2G can bind multidomain pro-apoptotic and anti-apoptotic Bcl-2 family proteins and contains two BH3-like motifs near its N- and C-termini. Molecular modeling predicts that these BH3-like motifs have amphipathic α-helix structures and can dock onto the canonical groove of Bax and anti-apoptotic proteins as well as the trigger site of Bax. A chimeric tBid with its BH3 domain replaced with the C-terminal Nes2 BH3-like domain binds to Bax in cells. Furthermore, Nes2 BH3-like motif-containing fragments from the N- and the C-termini bind both pro-apoptotic and anti-apoptotic Bcl-2 proteins and promote cytochrome c release (indicative of apoptosis). Our results suggest that Nes2 acts as a BH3-only protein that regulates apoptosis by binding to the multidomain Bcl-2 family proteins.