The Inhibition of PP1γ2 by PKA Through SRC Initiates Sperm Motility in Tree Shrews

The serine/threonine phosphatase PP1γ2 plays a critical role in modulating epididymal sperm maturation and motility. Our previous work demonstrated that PP1γ2 regulates these processes in tree shrews via phosphorylation and dephosphorylation. This study further investigates the interactions among PP1γ2, SRC tyrosine kinase, and protein kinase A (PKA), along with their molecular mechanisms in regulating epididymal sperm motility in tree shrews.Using Western blotting, immunokinase assays, co-immunoprecipitation, and Ser/Thr phosphatase activity assays, we characterized key signaling dynamics. Results showed that Ser/Thr phosphatase activity was significantly higher in caput than in cauda epididymal spermatozoa (p < 0.05). Inhibiting PKA and SRC significantly increased Ser/Thr phosphatase activity and reduced cauda sperm motility (p < 0.05). Conversely, SRC activation with sc-3052 significantly reduced phosphatase activity in caput sperm (p < 0.05). We also found that SRC interacts with PP1γ2 in caudal sperm, and that both SRC and PKA activities were higher in caudal than in caput sperm, with SRC acting downstream of PKA. These results suggest that SRC kinase regulates sperm motility by inhibiting PP1γ2-mediated Ser/Thr phosphatase activity, under the regulatory control of PKA. This study provides a foundation for further investigation into PP1γ2's functions and reproductive regulatory mechanisms in tree shrew sperm.