Expression of α-gustducin and α-transducin, G proteins coupled with taste receptors, in boar sperm

Abstract

During the transit in the female genital tract, spermatozoa are exposed to an environment that varies in composition from the vagina to the oviduct. Because G proteins, α-gustducin and α-transducin, are accepted as markers of chemosensitive cells, this study was aimed at assessing whether these proteins are expressed in boar germ cells. Ejaculated sperm extracts were analyzed by Western blot, and indirect immunofluorescence was performed on testis sections, smears of epididymal and ejaculated spermatozoa, sperm cells after in vitro induction of capacitation and acrosome reaction (IVAR), and in sperm cells bound to zona pellucida during IVF. Based on immunoblot results, both G proteins are present in boar sperm. In the testicular tissue sections, α-gustducin and α-transducin positivity was recorded in the germinal cells near the tubular lumen, whereas no positive signal was evident in spermatogonia located in the outer region of the seminiferous tubules. α-Gustducin expression in epididymal and ejaculated spermatozoa was mainly detectable in both the acrosome and the principal piece of the tail, whereas α-transducin was confined to the acrosome and the midpiece. No changes after in vitro induction of capacitation and IVAR were observed, except for the disappearance of acrosomal positivity in reacted spermatozoa. In sperm bound to zona pellucida, the G protein signal was congruent with that observed in IVAR cells. To the best of our knowledge, this is the first description of α-transducin in mammalian sperm and the first description of α-gustducin in boar sperm. Further studies are needed to clarify the possible role of these G proteins in sperm physiology.

Keywords: G protein; Pig; Sperm; Taste receptor.