Journal Article

VAPB interacts with the mitochondrial protein PTPIP51 to regulate calcium homeostasis

Kurt J. De Vos, Gábor M. Mórotz, Radu Stoica, Elizabeth L. Tudor, Kwok-Fai Lau, Steven Ackerley, Alice Warley, Christopher E. Shaw and Christopher C.J. Miller

in Human Molecular Genetics

Volume 21, issue 6, pages 1299-1311
Published in print March 2012 | ISSN: 0964-6906
Published online November 2011 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/ddr559

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A proline to serine substitution at position 56 in the gene encoding vesicle-associated membrane protein-associated protein B (VAPB) causes some dominantly inherited familial forms of motor neuron disease including amyotrophic lateral sclerosis (ALS) type-8. VAPB is an integral endoplasmic reticulum (ER) protein whose amino-terminus projects into the cytosol. Overexpression of ALS mutant VAPBP56S disrupts ER structure but the mechanisms by which it induces disease are not properly understood. Here we show that VAPB interacts with the outer mitochondrial membrane protein, protein tyrosine phosphatase-interacting protein 51 (PTPIP51). ER and mitochondria are both stores for intracellular calcium (Ca2+) and Ca2+ exchange between these organelles occurs at regions of ER that are closely apposed to mitochondria. These are termed mitochondria-associated membranes (MAM). We demonstrate that VAPB is a MAM protein and that loss of either VAPB or PTPIP51 perturbs uptake of Ca2+ by mitochondria following release from ER stores. Finally, we demonstrate that VAPBP56S has altered binding to PTPIP51 and increases Ca2+ uptake by mitochondria following release from ER stores. Damage to ER, mitochondria and Ca2+ homeostasis are all seen in ALS and we discuss the implications of our findings in this context.

Journal Article.  8003 words.  Illustrated.

Subjects: Genetics and Genomics

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