Title: Signaling in sperm: toward a molecular understanding of the acquisition of sperm motility in the mouse epididymis.
Authors: Vadnais, Melissa L; Aghajanian, Haig K; Lin, Angel; Gerton, George L
Published In Biol Reprod, (2013 Nov)
Abstract: Sperm motility encompasses a wide range of events involving epididymal maturation and activation of biochemical pathways, most notably cyclic AMP (cAMP)-protein kinase A (PKA) activation. Following the discovery of guanine-nucleotide exchange factors (RAPGEFs), also known as exchange proteins activated by cAMP, we investigated the separate roles of PKA and RAPGEFs in sperm motility. RT-PCR showed the presence of Rapgef3, Rapgef4, and Rapgef5, as well as several known RAPGEF partner mRNAs, in spermatogenic cells. However, Rapgef3 and Rapgef4 appeared to be less abundant in condensing spermatids versus pachytene spermatocytes. Similarly, many of these proteins were detected by immunoblotting. RAPGEF5 was detected in germ cells and murine epididymal sperm. Indirect immunofluorescence localized SGK1, SGK3, AKT1 pT(308), and RAPGEF5 to the acrosome, while PDPK1 was found in the postacrosomal region. SGK3 was present throughout the tail, while PDPK1 and AKT1 pT(308) were in the midpiece. When motility was assessed in demembranated cauda epididymal sperm, addition of ATP and the selective ligand for RAPGEFs, 8-pCPT-2'-O-Me-cAMP, resulted in motility, but the sperm were unable to undergo hyperactivated-like motility. In contrast, when demembranated cauda epididymal sperm were incubated with ATP plus dibutyryl cAMP, sperm became motile and progressed to hyperactivated-like motility. However, no significant difference was observed when intact sperm were examined. GSK3 phosphorylation was altered in the presence of H89, a PKA inhibitor. Significantly, intact caput epididymal sperm became motile when incubated in the presence of extracellular ATP. These results provide evidence for a new pathway involved in endowing sperm with the capacity to swim.
PubMed ID: 24006282
MeSH Terms: 3-Phosphoinositide-Dependent Protein Kinases/genetics; 3-Phosphoinositide-Dependent Protein Kinases/metabolism; Animals; Epididymis/cytology; Epididymis/metabolism*; Gene Expression; Guanine Nucleotide Exchange Factors/genetics; Guanine Nucleotide Exchange Factors/metabolism; Immediate-Early Proteins/genetics; Immediate-Early Proteins/metabolism; Male; Mice; Mice, Inbred C57BL; Protein-Serine-Threonine Kinases/genetics; Protein-Serine-Threonine Kinases/metabolism; Proto-Oncogene Proteins c-akt/genetics; Proto-Oncogene Proteins c-akt/metabolism; Rodentia/genetics; Rodentia/metabolism; Signal Transduction/genetics; Sperm Motility/genetics*; Spermatogenesis/genetics; Spermatozoa/metabolism; Spermatozoa/physiology*; Tissue Distribution