Splice-specific functions of gephyrin in molybdenum cofactor biosynthesis

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Item Type:	Article
Title:	Splice-specific functions of gephyrin in molybdenum cofactor biosynthesis
Creators Name:	Smolinsky, B., Eichler, S.A., Burchmeier, S., Meier, J.C. and Schwarz, G.
Abstract:	Gephyrin is a multifunctional protein involved in the clustering of inhibitory neuroreceptors. In addition, gephyrin catalyses the last step in molybdenum cofactor (Moco) biosynthesis essential for the activities of Mo-dependent enzymes such as sulfite oxidase and xanthine oxidoreductase. Functional complexity and diversity of gephyrin is believed to be regulated by alternative splicing in a tissue-specific manner. Here, we investigated eight gephyrin variants with combinations of seven alternatively spliced exons located in the N-terminal G domain, the central domain, and the C-terminal E domain. Their activity in Moco synthesis was analyzed in vivo by reconstitution of gephyrin-deficient L929 cells, which were found to be defective in the G domain of gephyrin. Individual domain functions were assayed in addition and confirmed that variants containing either an additional C5 cassette or missing the C6 cassette are inactive in Moco synthesis. In contrast, different alterations within the central domain retained Moco synthetic activity of gephyrin. Recombinant gephyrin G domain containing the C5 cassette forms dimers in solution, binds molybdopterin but is unable to catalyze MPT adenylylation. Determination of Moco and MPT content in different tissues showed that beside liver and kidney, brain was capable of synthesizing Moco most efficiently. Subsequent analysis of cultured neurons and glia cells demonstrated glial Moco synthesis, due to the expression of gephyrins containing cassettes C2 and C6 with and without C3.
Keywords:	Carrier Proteins, Cell Line, Coenzymes, Dimerization, Membrane Proteins, Metalloproteins, Biological Models, Chemical Models, Genetic Models, Neurons, Tertiary Protein Structure, Pteridines, RNA Splicing, Recombinant Proteins, Sulfite Oxidase, Xanthine Dehydrogenase, Animals, Mice
Source:	Journal of Biological Chemistry
ISSN:	0021-9258
Publisher:	American Society for Biochemistry and Molecular Biology
Volume:	283
Number:	25
Page Range:	17370-17379
Date:	20 June 2008
Official Publication:	https://doi.org/10.1074/jbc.M800985200
PubMed:	View item in PubMed

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