Human Molecular Genetics Advance Access published online on April 6, 2009
Human Molecular Genetics, doi:10.1093/hmg/ddp167
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TRIM32 is an E3 ubiquitin ligase for dysbindin
1 Department of Psychological Medicine, Cardiff University, Henry Wellcome Building, Heath Park, Cardiff. CF14 4XN. UK 2 Department of Pharmacology, University of Oxford, Mansfield Road, Oxford, OX1 3QT, UK 3 Present address: Department of Cardiovascular Medicine and the Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, OX3 7BN.
* Address for correspondence: Prof Derek J. Blake, Department of Psychological Medicine, Cardiff University, Henry Wellcome Building for Biomedical Research in Wales, Heath Park, Cardiff, CF14 4XN, UK Tel.: +44(0)29 2068 7051, Fax: +44(0)29 2068 7068 E-mail: blakedj{at}cardiff.ac.uk
Received December 15, 2008; Revised April 2, 2009; Accepted April 2, 2009
Mutations in the gene encoding tripartite motif protein 32 (TRIM32) cause two seemingly diverse diseases; limb-girdle muscular dystrophy type 2H (LGMD2H) or sarcotubular myopathy (STM) and Bardet-Biedl Syndrome type 11(BBS11). Whilst TRIM32 is involved in protein ubiquitination, its substrates and the molecular consequences of disease-causing mutations are poorly understood. In this paper we show that TRIM32 is a widely expressed ubiquitin ligase that is localised to the Z-line in skeletal muscle. Using the yeast two-hybrid system we found that TRIM32 binds and ubiquitinates dysbindin, a protein implicated in the genetic aetiology of schizophrenia, augmenting its degradation. siRNA-mediated knock-down of TRIM32 in myoblasts resulted in elevated levels of dysbindin. Importantly, the LGMD2H/STM-associated TRIM32 mutations, D487 N and R394H impair ubiquitin ligase activity towards dysbindin and were mislocalised in heterologous cells. These mutants were able to self-associate and also co-immunoprecipitated with wild-type TRIM32 in transfected cells. Furthermore, the D487 N mutant could bind to both dysbindin and its E2 enzyme but was defective in monoubiquitination. By contrast, the BBS11 mutant P130S did not show any biochemical differences compared to the wild-type protein. Our data identify TRIM32 as a regulator of dysbindin and demonstrate that the LGMD2H/STM mutations may impair substrate ubiquitination.
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  J. Tang, R. P. LeGros, N. Louneva, L. Yeh, J. W. Cohen, C.-G. Hahn, D. J. Blake, S. E. Arnold, and K. Talbot Dysbindin-1 in dorsolateral prefrontal cortex of schizophrenia cases is reduced in an isoform-specific manner unrelated to dysbindin-1 mRNA expression Hum. Mol. Genet., October 15, 2009; 18(20): 3851 - 3863. [Abstract] [Full Text] [PDF]
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