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J Cell Biochem. 2016 Nov;117(11):2597-607. doi: 10.1002/jcb.25554. Epub 2016 Apr 7.

Glycogen Synthase in Sertoli Cells: More Than Glycogenesis?

Author information

1
Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia 5090000, Chile.
2
Institute for Research in Biomedicine (IRB Barcelona) Barcelona, The Barcelona Institute of Science and Technology, Baldiri Reixac 10, Barcelona 08028, Spain.
3
Institució Catalana de Recerca i Estudis Avançats (ICREA), Barcelona, Spain.
4
Department of Biochemistry and Molecular Biology, University of Barcelona, Av. Diagonal 643, Barcelona 08028, Spain.
5
Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM), Madrid, Spain.
6
Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Valdivia 5090000, Chile. conchagrabinger@uach.cl.

Abstract

Sertoli cell metabolism actively maintains the nutritional needs of germ cells. It has been described that after glucose incorporation in Sertoli cells, less than 1% is converted to glycogen suggesting low levels of glycogen synthase activity. Phosphorylation of muscle glycogen synthase (MGS) at serine 640 (pS640MGS) decreases its activity, and this form of the enzyme was discovered as a non-ribosomal protein that modulates the translation of a subset of transcripts in HeLa cells. The aim of our study was to functionally characterize MGS in cultured Sertoli cells, as well as to explore this new feature related to RNA molecules. We detected MGS in the cytoplasm of Sertoli cells as well as in the nuclei. The activity rates of the enzyme were extremely low indicating that MGS is expressed but almost inactive. Protein targeting to glycogen (PTG) overexpression was performed to activate MGS by dephosphorylation. PTG induced glycogen synthesis massively, confirming that this enzyme is present but inactive. This finding correlates with high levels of pS640MGS, which were assayed by phosphatase treatment. To explore a putative new function for MGS in Sertoli cells, we performed RNA immunoprecipitation coupled to microarray studies. The results revealed that MGS co-immunoprecipitated with the several mRNAs and also rRNAs. These findings indicate that MGS is expressed Sertoli cells but in an inactive form, and also support a possibly novel feature of this metabolic enzyme associated with RNA-related molecules. J. Cell. Biochem. 117: 2597-2607, 2016.

KEYWORDS:

GLYCOGEN; GLYCOGEN SYNTHASE; RNA BINDING PROTEINS; RNAs; SERTOLI CELLS

PMID:
27017955
DOI:
10.1002/jcb.25554
[Indexed for MEDLINE]

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