Acetylcholinesterase‐R increases germ cell apoptosis but enhances sperm motility

Changes in protein subdomains through alternative splicing often modify protein‐protein interactions, altering biological processes. A relevant example is that of the stress‐induced up‐regulation of the acetylcholinesterase (AChE‐R) splice variant, a common response in various tissues. In germ cells of male transgenic TgR mice, AChE‐R excess associates with reduced sperm differentiation and sperm counts. To explore the mechanism(s) by which AChE‐R up‐regulation affects spermatogenesis, we identified AChE‐R's protein partners through a yeast two‐hybrid screen. In meiotic spermatocytes from TgR mice, we detected AChE‐R interaction with the scaffold protein RACK1 and elevated apoptosis. This correlated with reduced scavenging by RACK1 of the pro‐apoptotic TAp73, an outcome compatible with the increased apoptosis. In contrast, at later stages in sperm development, AChE‐R's interaction with the glycolytic enzyme enolase‐α elevates enolase activity. In transfected cells, enforced AChE‐R excess increased glucose uptake and adenosine tri‐phosphate (ATP) levels. Correspondingly, TgR sperm cells display elevated ATP levels, mitochondrial hyperactivity and increased motility. In human donors' sperm, we found direct association of sperm motility with AChE‐R expression. Interchanging interactions with RACK1 and enolase‐α may hence enable AChE‐R to affect both sperm differentiation and function by participating in independent cellular pathways.