Nerve Growth Factor Stimulates Interaction of Cayman Ataxia Protein BNIP-H/Caytaxin with Peptidyl-Prolyl Isomerase Pin1 in Differentiating Neurons

Jan Paul Buschdorf,Unice Jim Kim Soh,Li Li Chew,Boon Chuan Low,Yih-Cherng Liou,Mark R Cookson

doi:10.1371/journal.pone.0002686

Jan Paul Buschdorf, Unice Jim Kim Soh + Show 4 more

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https://doi.org/10.1371/journal.pone.0002686

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Journal: PloS one	Publication Date: Jul 16, 2008
Citations: 42	License type: CC BY 4.0

Affiliation: National University of Singapore

Abstract

Mutations in ATCAY that encodes the brain-specific protein BNIP-H (or Caytaxin) lead to Cayman cerebellar ataxia. BNIP-H binds to glutaminase, a neurotransmitter-producing enzyme, and affects its activity and intracellular localization. Here we describe the identification and characterization of the binding between BNIP-H and Pin1, a peptidyl-prolyl cis/trans isomerase. BNIP-H interacted with Pin1 after nerve growth factor-stimulation and they co-localized in the neurites and cytosol of differentiating pheochromocytoma PC12 cells and the embryonic carcinoma P19 cells. Deletional mutagenesis revealed two cryptic binding sites within the C-terminus of BNIP-H such that single point mutants affecting the WW domain of Pin1 completely abolished their binding. Although these two sites do not contain any of the canonical Pin1-binding motifs they showed differential binding profiles to Pin1 WW domain mutants S16E, S16A and W34A, and the catalytically inert C113A of its isomerase domain. Furthermore, their direct interaction would occur only upon disrupting the ability of BNIP-H to form an intramolecular interaction by two similar regions. Furthermore, expression of Pin1 disrupted the BNIP-H/glutaminase complex formation in PC12 cells under nerve growth factor-stimulation. These results indicate that nerve growth factor may stimulate the interaction of BNIP-H with Pin1 by releasing its intramolecular inhibition. Such a mechanism could provide a post-translational regulation on the cellular activity of BNIP-H during neuronal differentiation. (213 words)

Highlights

BNIP-H is a brain-specific protein and mutations in its gene ATCAY cause human cayman cerebellar ataxia [1]
BNIP-H binds to Pin1 after NGF-stimulation in PC12 cells BNIP-H contains a C-terminal BNIP-2 and Cdc42GAP homology (BCH) domain and an N-terminus with no obvious similarity to any known protein domain
In the absence of NGF very weak binding was detected while the N-terminal BNIPH fragment did not show any interaction in either condition (Fig. 1A). These data suggest that the binding between BNIP-H and Pin1 in PC12 cells is induced by NGF

Summary

Introduction

BNIP-H (or Caytaxin) is a brain-specific protein and mutations in its gene ATCAY cause human cayman cerebellar ataxia [1]. The same gene is affected in three different mutant mice, jittery, sidewinder and hesitant [1,3,4]. Hesitant mice show mild ataxia and dystonia whereas jittery and sidewinder mice have severe limb and truncal ataxia, dystonic forelimb spasms and die at the age of 3–4 weeks. Xiao et al [9] recently analyzed differential gene expression of dystonic and normal rats and implicated the possible involvement of phosphatidylinositol signaling pathways, calcium homeostasis and extracellular matrix interactions, while in another study, BNIP-H was found to be polyubiquitinated by the ubiquitin E3 ligase CHIP (Cterminus of Hsc70-interacting protein) in vitro, suggesting that BNIP-H degradation could be triggered by CHIP [10]

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