Human spermatozoa possess a calcium‐dependent chloride channel that may participate in the acrosomal reaction

Key points • Ion channels participate in crucial sperm functions such as motility, capacitation and the acrosome reaction. • Chloride, the main anion in physiological solutions, is deeply involved in sperm physiology. • We implemented a modified perforated patch‐clamp strategy to obtain whole cell recordings sealing on the head of mature human spermatozoa to investigate their ion channels. • This work presents the first evidence for the presence of calcium‐dependent chloride channels (CaCCs) in human spermatozoa; they could be constituted by TMEM16. • The CaCCs play an important role in the physiology of human spermatozoa and participate in the acrosome reaction. Motility, maturation and the acrosome reaction (AR) are fundamental functions of mammalian spermatozoa. While travelling through the female reproductive tract, spermatozoa must mature through a process named capacitation, so that they can reach the egg and undergo the AR, an exocytotic event necessary to fertilize the egg. Though Cl− is important for sperm capacitation and for the AR, not much is known about the molecular identity of the Cl− transporters involved in these processes. We implemented a modified perforated patch‐clamp strategy to obtain whole cell recordings sealing on the head of mature human spermatozoa. Our whole cell recordings revealed the presence of a Ca2+‐dependent Cl− current. The biophysical characteristics of this current and its sensitivity to niflumic acid (NFA) and 4,4′‐diisothiocyano‐2,2′‐stilbene disulphonic acid (DIDIS) are consistent with those displayed by the Ca2+‐dependent Cl− channel from the anoctamin family (TMEM16). Whole cell patch clamp recordings in the cytoplasmic droplet of human spermatozoa corroborated the presence of these currents, which were sensitive to NFA and to a small molecule TMEM16A inhibitor (TMEM16Ainh, an aminophenylthiazole). Importantly, the human sperm AR induced by a recombinant human glycoprotein from the zona pellucida, rhZP3, displayed a similar sensitivity to NFA, DIDS and TMEM16Ainh as the sperm Ca2+‐dependent Cl− currents. Our findings indicate the presence of Ca2+‐dependent Cl− currents in human spermatozoa, that TMEM16A may contribute to these currents and also that sperm Ca2+‐dependent Cl− currents may participate in the rhZP3‐induced AR.