Autophagy-Related Proteins Influence Mouse Epididymal Sperm Motility.

Autophagy is an intracellular process that recycles and degrades cytoplasmic components, including organelles and macromolecules, to provide energy and basic components for cell survival, maintain cellular homeostasis, and avoid self-damage. It is currently not fully known if mouse sperm undergoes the autophagy process, nor is the subcellular distribution, protein levels of autophagy-related proteins, and the biological role of autophagy in epididymal mouse sperm physiology fully understood. We aimed to investigate key autophagy markers, including LC3 (microtubule-associated protein 1A/1B-light chain 3), p62/SQSTM1 (Sequestosome 1), and mTOR (mechanistic Target of Rapamycin), in epididymal mouse sperm under capacitation (Cap) or non-capacitation (NC) conditions. Furthermore, we evaluated the possible role of these autophagy-related proteins on sperm viability, motility, intracellular pH (pHi), intracellular calcium concentrations [Ca(2+)]i, mitochondrial membrane potential, and acrosome reaction (AR) induction in the presence or absence of chloroquine (CQ), K67, and rapamycin. Our results suggest a dynamic re-localization of the autophagy-related proteins LC3, p62/SQSTM1, and mTOR under capacitation conditions. Moreover, treatment with specific autophagy inhibitors, such as CQ and K67, resulted in decreased LC3-II and p62/SQSTM1 protein levels. Additionally, rapamycin did not increase mTOR levels. Interestingly, treatment with these inhibitors also resulted in decreased motility, reduced mitochondrial membrane potential and hindered AR induction without affecting sperm viability. Overall, the presence and dynamic re-localization of LC3, p62/SQSTM1, and mTOR suggest that mouse epididymal sperm could perform initial steps of autophagy under capacitation conditions, and results of the pharmacological treatment could be associated with an important role of these autophagy-related proteins in sperm motility and AR induction.