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A Developmentally Regulated, Neuron-specific Splice Variant of the Variable Subunit Bβ Targets Protein Phosphatase 2A to Mitochondria and Modulates Apoptosis
Journal article   Open access   Peer reviewed

A Developmentally Regulated, Neuron-specific Splice Variant of the Variable Subunit Bβ Targets Protein Phosphatase 2A to Mitochondria and Modulates Apoptosis

Ruben K Dagda, Julie A Zaucha, Brian E Wadzinski and Stefan Strack
The Journal of biological chemistry, Vol.278(27), pp.24976-24985
07/04/2003
DOI: 10.1074/jbc.M302832200
PMID: 12716901
url
https://doi.org/10.1074/jbc.M302832200View
Published (Version of record) Open Access

Abstract

Heterotrimeric protein phosphatase 2A (PP2A) is a major Ser/Thr phosphatase composed of catalytic, structural, and regulatory subunits. Here, we characterize Bbeta2, a novel splice variant of the neuronal Bbeta regulatory subunit with a unique N-terminal tail. Bbeta2 is expressed predominantly in forebrain areas, and PP2A holoenzymes containing Bbeta2 are about 10-fold less abundant than those containing the Bbeta1 (previously Bbeta) isoform. Bbeta2 mRNA is dramatically induced postnatally and in response to neuronal differentiation of a hippocampal progenitor cell line. The divergent N terminus of Bbeta2 does not affect phosphatase activity but encodes a subcellular targeting signal. Bbeta2, but not Bbeta1 or an N-terminal truncation mutant, colocalizes with mitochondria in neuronal PC12 cells. Moreover, the Bbeta2 N-terminal tail is sufficient to target green fluorescent protein to this organelle. Inducible or transient expression of Bbeta2, but neither Bbeta1, Bgamma, nor a Bbeta2 mutant defective in holoenzyme formation, accelerates apoptosis in response to growth factor deprivation. Thus, alternative splicing of a mitochondrial localization signal generates a PP2A holoenzyme involved in neuronal survival signaling.

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