Simultaneous activation of PLA2 and PLC are required to promote acrosomal reaction stimulated by progesterone via G‐proteins

Abstract

The acrosome reaction (AR) is a special exocytotic process promoted by signal transduction pathways studied in many laboratories. Progesterone (P4) is one of the trigger molecules proposed. Upon the binding of P4 to its receptor, several molecules could be activated, including G-proteins, phospholipase A(2) (PLA(2)), and phospholipase C (PLC). The role of these molecules was analyzed in this study using the Chlortetracycline (CTC) protocol to detect and quantify the AR. Incubation of capacitated sperm cells with GTPgammas (GTPgammas, a mimetic of G-protein activation), arachidonic acid (AA, product of PLA(2) action), or phorbol ester (PMA, an activator of PLC) for 15 min increased the AR to a similar percentage as P4. Conversely, a decrease in the AR was detected when sperm cells were incubated with P4 after preincubation with: GDPbetaS (GDP, an inhibitor of G-protein activation), ONO RS-82 (ONO, an inhibitor of PLA(2)), or neomycin (Neo, an inhibitor of PLC) for 15 min. To analyze the activation sequence of G proteins, PLA(2), and PLC combinations of these mimetic/inhibitors were used during successive incubation periods. Inhibition promoted by GDP, ONO, and Neo were overcome by 15-min incubation with GTPgammas, AA, or PMA, respectively. But GTPgammas or P4 did not reverse the inhibition due to incubation with Neo and ONO. Interestingly, this dual inhibition was reverted by another 15-min incubation with AA or PMA. Results presented here could indicate that the AR triggered by P4 is driven by activation of G-proteins, that in turn activate PLA(2) and PLC simultaneously, that finally promote acrosomal exocytosis.

Group X phospholipase A2 is released during sperm acrosome reaction and controls fertility outcome in mice

“…As for capacitation, a spontaneous release of PAF during capacitation has been linked to activation of spontaneous AR, but the enzyme responsible for PAF release has not been identified (30). As for AR, induction of AR using nonphysiological and physiological stimuli such as Ca 2+ ionophore, progesterone, and ZP produces the release of arachidonic acid and/or lysophosphatidylcholine (LPC) and is prevented by PLA 2 inhibitors on sperm from various species (31)(32)(33)(34). However, the identity of the PLA 2 (s) involved in this exocytotic event has not yet been revealed, and the use of poorly specific PLA 2 inhibitors such as Ro-31-4493, aristolochic acid, or ONO RS-82 in these studies cannot provide any clue (31,33,34).…”

“…As for AR, induction of AR using nonphysiological and physiological stimuli such as Ca 2+ ionophore, progesterone, and ZP produces the release of arachidonic acid and/or lysophosphatidylcholine (LPC) and is prevented by PLA 2 inhibitors on sperm from various species (31)(32)(33)(34). However, the identity of the PLA 2 (s) involved in this exocytotic event has not yet been revealed, and the use of poorly specific PLA 2 inhibitors such as Ro-31-4493, aristolochic acid, or ONO RS-82 in these studies cannot provide any clue (31,33,34). PLA 2 activation during AR is also supported by the fact that LPC and fatty acids accelerate or promote exocytosis (35,36).…”

NYD-SP27, a novel intrinsic decapacitation factor in sperm

“…In fact, our earlier study in pancreatic duct cells has showed that NYD-SP27 acts as a physical PLC inhibitor [7]. In this study, Ca 2+ mobilization in sperm induced by either extracellular ATP or progesterone, whose receptors are known to be coupled to PLC [13,[21][22][23], was inhibited by both PLC inhibitor and retention of mNYD-SP27 in sperm by its antiserum. Taken together, these observations show that capacitation is made possible only if NYD-SP27, an intrinsic decapacitation factor, is removed from sperm.…”

“…This leads to increased intracellular Ca 2+ and activation of PKC, and finally, the acrosome reaction [13]. On the other hand, progesterone induces the acrosome reaction by binding to its receptor, leading to activation of PLC and PLA 2 simultaneously [22,23], and the progesterone-induced acrosome reaction can be prevented only when both PLC and PLA 2 inhibitors are present. The present results indeed show that both PLC inhibitor and mNYD-SP27 retention almost completely abolished the ATP-induced acrosome reaction, but with less effect on the progesterone-induced acrosome reaction.…”

Functional aspects of seminal plasma and sperm proteins and their potential as molecularmarkers of fertility

“…Seminal plasma phospholipase A2 (PLA2) participates in capacitation, acrosome reaction and sperm-oocyte membrane fusion (Soubeyrand et al, 1997;Pietrobon et al, 2005;Roldan and Shi, 2007). PLA2 also has antimicrobial effects and its expression in seminal plasma is associated with fertility in bulls (Moura et al, 2006).…”