HSP90 maintains boar spermatozoa motility and mitochondrial membrane potential during heat stress

•A protective effect of HSP90 on boar sperm subjected to heat stress is demonstrated.•HSP90 inhibition by 17-AAG decreases boar sperm motility in non-capacitating conditions after 24 h.•The decrease in boar sperm motility is more pronounced under heat stress conditions (40 °C) in presence of 17-AAG.•Mitochondrial membrane potential of non-capacitated boar sperm decreases in presence of 17-AAG under heat stress after 24 h. Heat Shock Proteins (HSP) is a family of proteins that protects cells from high temperatures. The present work aimed to elucidate the role that HSP90 exerts on boar sperm incubated under heat stress conditions on viability, total motility (TM), progressive motility (PM), acrosome status, mitochondrial membrane potential and plasma membrane lipid organization. Sperm were incubated in non-capacitating conditions (Tyrode’s basal medium or TBM) for 3, 8 and 24 h or in capacitating conditions (Tyrode’s complete medium or TCM) for 4 h at 38.5 °C or 40 °C (Heat stress) in the presence or absence of 5 or 20 μM of 17-AAG, a specific HSP90 inhibitor. Sperm viability was not affected by the presence of 17-AAG in any condition tested compared with its own control (at the same temperature and incubation time). In non-capacitating conditions TM (22.7 ± 4.1 vs. 1.9 ± 1.1; % mean ± SEM), PM (3.1 ± 0.9 vs. 0) and high mitochondrial membrane potential (19.5 ± 2.2 vs. 11.8 ± 0.8) decreased significantly in sperm incubated at 40 °C for 24 h in the presence of 20 μM 17-AAG (control vs. 20 μM 17-AAG, respectively; p