Molecular Insights into PKA Activity Modulation by Lysine Acetylation

Background Mammalian sperm capacitation is a critical maturation process regulated by the cAMP-dependent protein kinase A (PKA) signaling axis. While cAMP levels peak early and decline during capacitation, PKA activity remains paradoxically sustained. Methods Here, we used a combination of in vitro acetylation assays, enzyme kinetic analysis, nuclear magnetic resonance (NMR) spectroscopy, and mass spectrometry to shed light on this knowledge gap. Results We identified lysine acetylation as a novel post-translational modification that modulates PKA activity and localization in mouse sperm. Acetylation of the PKA catalytic subunit (PKA-C) enhances its activity by increasing its binding affinity for ATP, suggesting the existence of cAMP-independent regulatory mechanisms. Furthermore, we show that acetylation promotes the dissociation of the PKA holoenzyme, mimicking the activating effect of cAMP. Conclusions These findings uncover a multimodal regulatory mechanism where lysine acetylation acts independent of cAMP to sustain PKA signaling during sperm maturation. Our study provides a molecular basis for the persistent activation of PKA in transcriptionally silent cells and highlights a potentially conserved regulatory principle for this ubiquitous eukaryotic protein kinase family.