title: Muscle glycogen synthase isoform is responsible for testicular glycogen synthesis: glycogen overproduction induces apoptosis in male germ cells.
abstract: Glycogen is the main source of glucose for many biological events. However, this molecule may have other functions, including those that have deleterious effects on cells. The rate-limiting enzyme in glycogen synthesis is glycogen synthase (GS). It is encoded by two genes, GYS1, expressed in muscle (muscle glycogen synthase, MGS) and other tissues, and GYS2, primarily expressed in liver (liver glycogen synthase, LGS). Expression of GS and its activity have been widely studied in many tissues. To date, it is not clear which GS isoform is responsible for glycogen synthesis and the role of glycogen in testis. Using RT-PCR, Western blot and immunofluorescence, we have detected expression of MGS but not LGS in mice testis during development. We have also evaluated GS activity and glycogen storage at different days after birth and we show that both GS activity and levels of glycogen are higher during the first days of development. Using RT-PCR, we have also shown that malin and laforin are expressed in testis, key enzymes for regulation of GS activity. These proteins form an active complex that regulates MGS by poly-ubiquitination in both Sertoli cell and male germ cell lines. In addition, PTG overexpression in male germ cell line triggered apoptosis by caspase3 activation, proposing a proapoptotic role of glycogen in testis. These findings suggest that GS activity and glycogen synthesis in testis could be regulated and a disruption of this process may be responsible for the apoptosis and degeneration of seminiferous tubules and possible cause of infertility.
authors: Instituto de Bioquímica y Microbiología, Universidad Austral de Chile, Valdivia, Chile.
authors: Franz
authors: F
authors: Villarroel-Espíndola
authors: Rodrigo
authors: R
authors: Maldonado
authors: Héctor
authors: H
authors: Mancilla
authors: Karen
authors: K
authors: vander Stelt
authors: Aníbal I
authors: AI
authors: Acuña
authors: Alejandra
authors: A
authors: Covarrubias
authors: Camila
authors: C
authors: López
authors: Constanza
authors: C
authors: Angulo
authors: Maite A
authors: MA
authors: Castro
authors: Juan Carlos
authors: JC
authors: Slebe
authors: Jordi
authors: J
authors: Durán
authors: Mar
authors: M
authors: García-Rocha
authors: Joan J
authors: JJ
authors: Guinovart
authors: Ilona I
authors: II
authors: Concha
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000235:genetics / Q000502:physiology; D005854:Germ Cells / Q000166:cytology* / Q000378:metabolism*; D006003:Glycogen / Q000378:metabolism*; D006006:Glycogen Synthase / Q000235:genetics / Q000378:metabolism*; D015151:Immunoblotting; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012671:Seminiferous Tubules / Q000166:cytology / Q000378:metabolism; D013737:Testis / Q000166:cytology* / Q000201:enzymology / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D006003:Glycogen; D006006:Glycogen Synthase