Extracellular Signal-Regulated Kinases Modulate Capacitation of Human Spermatozoa1

Abstract

Recent evidence indicates the presence of p21 Ras and of a protein with characteristics similar to mitogen-activated protein kinases (MAPKs), also known as extracellular signal-regulated kinases (ERKs), in mammalian spermatozoa, suggesting the occurrence of the Ras/ERK cascade in these cells. In the present study we investigated the subcellular localization of ERKs and their biological functions in human spermatozoa. Immunohistochemistry, immunofluorescence, confocal microscopy, and immunoelectron microscopy demonstrated localization of ERKs in the postacrosomal region of spermatozoa. After stimulation of acrosome reaction with the calcium ionophore A23187 and progesterone, ERKs were mostly localized at the level of the equatorial region, indicating redistribution of these proteins in acrosome-reacted spermatozoa. Two proteins of 42 and 44 kDa that are tyrosine phosphorylated in a time-dependent manner during in vitro capacitation were identified as p42 (ERK-2) and p44 (ERK-1) by means of specific antibodies. The increase in tyrosine phosphorylation of these proteins during capacitation was accompanied by increased kinase activity, as determined by the ability of ERK-1 and ERK-2 to phosphorylate the substrate myelin basic protein. The role of this activity in the occurrence of sperm capacitation was also investigated by using PD098059, an inhibitor of the MAPK cascade. The presence of this compound during in vitro capacitation inhibits ERK activation and significantly reduces the ability of spermatozoa to undergo the acrosome reaction in response to progesterone. Since only capacitated spermatozoa are able to respond to progesterone, these data strongly indicate that ERKs are involved in the regulation of capacitation. In summary, our data demonstrate the presence of functional ERKs in human spermatozoa and indicate that these enzymes are involved in activation of these cells during capacitation, providing new insight in clarifying the molecular mechanisms and the signal transduction pathways of this process.

FGFR-1 signaling is involved in spermiogenesis and sperm capacitation

“…The level at which this suppression occurs is not known, however, it is upstream of ERK 1/2. FGFR-1 in sperm development and function suppressed capacitation and is consistent with previously published data indicating that the MAPK activation is involved in capacitation (Ashizawa et al, 1997;de Lamirande and Gagnon, 2002;Luconi et al, 1998;O'Flaherty et al, 2005). It suggests that FGFR-1/PI3K activation acts either directly or indirectly on MAPK activation.…”

“…As shown in Fig. 3B, and consistent with previously published data on human sperm (de Lamirande and Gagnon, 2002;Luconi et al, 1998), the MAPK pathway, as indicated by an increase in ERK1/2 phosphorylation, became activated during BWW induced capacitation of wild-type sperm ie. time 0 minutes versus time 90 minutes.…”

“…The regulation of global sperm tyrosine phosphorylation associated with capacitation is a complex process that probably involves input from several signaling pathways including the MAPK pathway, PKA, A1 adenosine receptor, and the platelet activating factor (PAF) receptor signaling (de Lamirande and Gagnon, 2002;Luconi et al, 1998;Minelli et al, 2004;Muguruma and Johnston, 1997;Roudebush et al, 2005;Wu et al, 2001). It is absolutely dependent upon cholesterol efflux (and an associated increase in membrane fluidity), bicarbonate and Ca 2+ influxes (Carlson et al, 2003;Davis and Gergely, 1979;Gadella and Harrison, 2000;Ho and Suarez, 2001).…”

Changes in content and localization of proteins phosphorylated at tyrosine, serine and threonine residues during ram sperm capacitation and acrosome reaction

“…Besides the well-characterized protein kinase A (PKA), other Ser/Thr kinases and the ERKs have been involved in sperm capacitation and acrosome reaction (Luconi et al 1998, du Plessis et al 2001, Liguori et al 2005. More recently, specific targets to PKA phosphorylation has been established in human (O'Flaherty et al 2004, Moseley et al 2005) and boar sperm (Harrison 2004).…”

SPINKL, a Kazal-type serine protease inhibitor-like protein purified from mouse seminal vesicle fluid, is able to inhibit sperm capacitation

“…Several signal transduction pathways have been demonstrated to be associated with sperm capacitation, including the extracellular signal-regulated kinase pathway (Luconi et al 1998, de Lamirande & Gagnon 2002, the cyclic AMP/protein kinase A pathway (Visconti et al 1995b, Breitbart 2003, and the reactive oxygen species affected pathway (de Lamirande & O'Flaherty 2008). We can speculate that SPINKL may affect the capacitation-related signal transduction machinery of sperm.…”