The BNIP-2 and Cdc42GAP Homology/Sec14p-like Domain of BNIP-Sα Is a Novel Apoptosis-inducing Sequence

Yi Ting Zhou,Unice J.K Soh,Xun Shang,Graeme R Guy,Boon Chuan Low

doi:10.1074/jbc.m109459200

Yi Ting Zhou, Unice J.K Soh + Show 3 more

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https://doi.org/10.1074/jbc.m109459200

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Abstract

We have cloned the cDNAs for two novel human proteins, designated BNIP-Salpha and beta (for BNIP-2 Similar) that are homologous to BNIP-2, a previously known Bcl-2 and E1B-associated protein. The BNIP-S gene encodes two protein isoforms; the longer protein (BNIP-Salpha) contains a complete BNIP-2 and Cdc42GAP Homology (BCH) domain, a novel protein domain that we recently identified, whereas its shorter variant (BNIP-Sbeta) lacks the full BCH domain as a result of an alternative RNA splicing that introduces a nonsense intron. Primer-specific reverse-transcription PCR revealed that both BNIP-Salpha and BNIP-Sbeta mRNA are differentially expressed in various cells and tissues. The expression of BNIP-Salpha or the complete BCH domain, but not BNIP-Sbeta, causes extensive apoptosis in cells. Furthermore, BNIP-Salpha can form a homophilic complex via a unique sequence motif within its BCH domain, and deletion of this interacting motif prevents its pro-apoptotic effect. These results indicate the presence of two BNIP-S splicing variants as cellular regulators and that the BCH domain of BNIP-Salpha confers a novel apoptotic function. The significance of this is discussed.

Highlights

We have cloned the cDNAs for two novel human proteins, designated BNIP-S␣ and ␤ that are homologous to BNIP-2, a previously known Bcl-2 and E1B-associated protein
It was observed that the deletion-S mutant failed to exert proapoptotic activity, whereas deletion mutants of region R and T were just as potent as the wild type (Fig. 8B). These findings suggest that the homophilic interaction of BNIP-S␣ via the BNIP-2 and Cdc42GAP Homology (BCH) domains coincides with its apoptotic effects
In this work we report the cloning and characterization of two novel isoforms that are homologous to BNIP-2

Summary

Introduction

We have cloned the cDNAs for two novel human proteins, designated BNIP-S␣ and ␤ (for BNIP-2 Similar) that are homologous to BNIP-2, a previously known Bcl-2 and E1B-associated protein. BNIP-S␣ can form a homophilic complex via a unique sequence motif within its BCH domain, and deletion of this interacting motif prevents its pro-apoptotic effect These results indicate the presence of two BNIP-S splicing variants as cellular regulators and that the BCH domain of BNIP-S␣ confers a novel apoptotic function. Interaction domains within proteins were relatively recently discovered many are still being revealed and characterized, and few are understood in depth These domains can either serve as protein docking/interaction sites, where multiple proteins can associate to form a functional complex or they may take part in binding to other molecules such as DNA or lipids, or be involved in enzymatic reactions [1,2,3,4,5]. Additional domains that are important for apoptosis remain to be identified, and the full extent of their various interactions and regulation need to be fully characterized in order to obtain an integrated perspective of apoptosis

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