Protease activation and the signal transduction pathway regulating motility in sperm from the water strider Aquarius remigis

Abstract

Many motile processes are regulated such that movement occurs only upon activation of a signaling cascade. Sperm from a variety of species are initially quiescent and must be activated prior to beating. The signaling events leading to the activation and regulation of sperm motility are not well characterized. Mature seminal vesicle sperm from the water strider Aquarius remigis are immotile in vitro, but vigorous motility is activated by trypsin. Trypsin-activated motility was blocked by pretreatment of the sperm with BAPTA-AM to chelate intracellular Ca(2+) and was partially rescued by subsequent addition of A23187 and Ca(2+). Thapsigargin stimulated motility in the absence of trypsin, suggesting that intracellular Ca(2+) stores are available. In addition, motility could be fully activated by the phosphatase inhibitor calyculin A, suggesting that the immotile state is maintained by an endogenous phosphatase and that kinase activity is required for motility. The MEK1/2 inhibitor U0126 significantly reduced trypsin activated motility, and MPM-2, an antibody which recognizes proline-directed phosphorylation by kinases such as MAPK, recognized components of the water strider sperm flagellum. Antibodies specific for the mouse protease activated receptor PAR2 recognized an antigen on the sperm flagellum. These results suggest that trypsin stimulates a Ca(2+) and MAPK mediated signaling pathway and potentially implicate a PAR2-like protein in regulating motility.

Transcriptome characterization of male accessory glands in ants to identify molecules involved in their reproductive success

“…These have also been identified in the male accessory glands or seminal fluid of other taxa such as honeybees, mosquitoes, beetles and field crickets (Dottorini et al ., ; Baer et al ., ; Simmons et al ., ; Xu et al ., ), and have also been detected in female sperm storage organs of C. osakensis (Gotoh et al ., ) and D. melanogaster (Allen & Spradling, ; Prokupek et al ., ). In males of some insect species, serine proteases induce sperm motility and maturation (Osanai et al ., ; Friedländer et al ., ; Miyata et al ., ; Nagaoka et al ., ). However, ant spermatozoa are immobilized after ejaculation by males and during storage by queens (see above), therefore the proteolysis regulator proteins found in this study may have no functions to induce sperm motility.…”

Proteolytic Activation of the Protease-activated Receptor (PAR)-2 by the Glycosylphosphatidylinositol-anchored Serine Protease Testisin

“…Both testisin and PAR-2 are expressed on the head region and midpiece of human spermatozoa (55). Whether testisin functions as an endogenous activator of PAR-2 in sperm is not known, but PAR-2 activation has been associated with the regulation of sperm motility following trypsin activation (55,56).…”

Culex pipiens sperm motility is initiated by a trypsin‐like protease from male accessory glands

“…In some organisms, chemical factors that activate sperm motility are released by the egg and, therefore, represent the first communication between sperm and egg. In several insect taxa, the initiation of motility is activated by trypsin‐like serine proteases (Friedländer, Jeshtadi, & Reynolds, ; Osanai & Baccetti, ; Miyata et al, ; Thaler et al, ).…”

“…Endogenous proteases also activate sperm motility in another group of lepidopterans, the Saturniid moths (Shepherd, ,), although whether the mechanism involves generation of free arginines is not clear. In contrast, sperm from the water strider Aquarius remigis are directly activated by trypsin via a protease‐activated receptor 2 (PAR2) pathway that triggers a downstream MAPK signaling cascade (Miyata, Thaler, Haimo, & Cardullo, ). Similarly, sperm motility in Culex mosquitoes can be activated by trypsin stimulation of a MAPK pathway that induces a transition from a weakly oscillating waveform to rapid forward progressive motility of sperm (Thaler et al, ).…”