Group X secreted phospholipase A₂ specifically decreases sperm motility in mice

Abstract

Different mammalian secreted phospholipases A(2) (sPLA(2) s) are expressed in male reproductive organs and/or in sperm cells but their cellular functions are still not fully characterized. Because several reports indicate a link between cellular lipids and sperm motility, we have investigated the effect of mouse group IIA, IID, IIE, V, and X sPLA(2) s on sperm motility. Among these enzymes, only mouse group X sPLA(2) (mGX sPLA(2) ) acts as a potent inhibitor of sperm motility that decreases track speed (VCL) and lateral displacement of the head (ALH) of both noncapacitated and capacitated sperm. The inhibitory effect of mGX sPLA(2) is dependent on its enzymatic activity because (i) both the proenzyme form of mGX sPLA(2) (pro-mGX) and the H48Q mutant of mGX sPLA(2) have very weak enzymatic activity and are unable to modulate sperm motility and (ii) LY329722, a specific inhibitor of sPLA(2) s, blocks the inhibitory effect of mGX sPLA(2) . Moreover, mGX sPLA(2) exerts a gradual potency on sperm subpopulations with different velocities, an effect which may be linked to the heterogeneity of lipid composition in these sperm subpopulations. Finally, we found that endogenous mGX sPLA(2) released during spontaneous acrosome reaction modulates sperm motility of capacitated sperm. Together, our results suggest a new role of sPLA(2) in sperm physiology where the sPLA2 selects a sperm subpopulation for fertilization based on its effect on sperm motility.

Progesterone-induced Acrosome Exocytosis Requires Sequential Involvement of Calcium-independent Phospholipase A2β (iPLA2β) and Group X Secreted Phospholipase A2 (sPLA2)

“…In mature mouse sperm, the group X sPLA 2 (mGX) is located in the acrosome and is released during the AR (24). It specifically improves fertilization and early embryo development (24,27,28).…”

Diverse Functions of Secretory Phospholipases A2

“…Further they reported that spermatozoa from GX KO mice exhibited lower rates of spontaneous AR and that this was associated with decreased in vitro fertilization (IVF) efficiency due to a drop in the fertilization potential of the sperm and an increased rate of aborted embryos. Mouse GX sPLA 2 acts as a potent inhibitor of sperm motility of both capacitated and noncapacitated sperms [82]. Though the mechanism for this regulation is unclear, this effect of GX sPLA 2 is dependent on its catalytic function and hence might involve changes in phospholipid metabolism.…”

“…Though the mechanism for this regulation is unclear, this effect of GX sPLA 2 is dependent on its catalytic function and hence might involve changes in phospholipid metabolism. It is also found that endogenous GX sPLA 2 is spontaneously released during acrosome reaction and modulates motility of capacitated sperms [82]. Mouse GX sPLA 2 has a unique property of improving fertilization outcome during capacitation [83] and hence has a unique usefulness in improving outcomes in in vitro fertilization.…”

Les phospholipases, enzymes clés de la physiologie spermatique

“…La sPLA 2 -GX sécrétée au cours de la capacitation inhibe quant à elle la mobilité flagellaire. Cependant, l'enzyme semble cibler plus particulièrement les spermatozoïdes dont la mobilité est déficiente, en rapport avec une composition lipidique membranaire particulière [25].…”

“…Ces résultats suggèrent que les modifications lipidiques induites par la sPLA 2 -GX au cours de la capacitation sont importantes pour insérer dans le spermatozoïde des messagers lipidiques secondaires favorisant le déve-loppement embryonnaire précoce. La sélection des spermatozoïdes reposerait donc, dans un premier temps, sur la traversée du mucus cervical, puis sur les interactions entre les spermatozoïdes et les cellules épithéliales utérotubaires [28] et, finalement, sur le contrôle de la réaction acrosomique précoce par la sPLA 2 -GX [25].…”