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Immunolocalization of multiple Gα subunits in mammalian spermatozoa and additional evidence for Gα s
Author(s) -
Baxendale Rhona W.,
Fraser Lynn R.
Publication year - 2003
Publication title -
molecular reproduction and development
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.745
H-Index - 105
eISSN - 1098-2795
pISSN - 1040-452X
DOI - 10.1002/mrd.10295
Subject(s) - biology , heterotrimeric g protein , g protein , gs alpha subunit , spermatozoon , cholera toxin , adenylyl cyclase , microbiology and biotechnology , receptor , flagellum , protein subunit , signal transduction , biochemistry , human fertilization , endocrinology , anatomy , gene
Like somatic cells, mammalian spermatozoa appear to contain several different heterotrimeric G protein α‐subunits that could mediate specialized cell responses. However, the precise Gα subunits present, their subcellular location and their possible roles are still incompletely defined. In this study, using commercially available specific antibodies, we have shown by immunoblotting that Gα s is present in human and mouse sperm lysates. Immunolocalization using intact spermatozoa from both species revealed this protein to be in the acrosomal cap region and the flagellum, particularly the principal piece. Treatment of permeabilized mouse spermatozoa with cholera toxin led to enhanced ADP‐ribosylation of a protein the same size as Gα s , as well as an increase in cAMP, providing further proof for Gα s . Evidence for the presence and distinct localizations of Gα i2 , Gα i3 , Gα o , Gα q/11 , and Gα olf was also obtained. Of particular interest was Gα i2 which, like Gα s , was present in the acrosomal cap region and flagellum, the same regions where stimulatory and inhibitory adenosine receptors are localized. These observations are consistent with our hypothesis that G proteins mediate adenosine receptor modulation of adenylyl cyclase, with consequent alterations in cAMP production, apparently crucial for the spermatozoon's acquisition and maintenance of fertilizing ability. Mol. Reprod. Dev. 65: 104–113, 2003. © 2003 Wiley‐Liss, Inc.