F‐actin involvement in guinea pig sperm motility

Abstract

Sperm motility is a must for natural fertilization to occur. During their travel through the epididymis, mammalian spermatozoa gradually acquire the ability to move. This is accomplished through a sliding movement of the outer doublet microtubules of the axoneme which is energized by the dynein ATPase. Within its complex structure, the mammalian sperm flagellum contains F-actin and thus, we decided to test in the guinea pig sperm flagellum the role of F-actin in motility. During maturation, capacitation, and the acrosome reaction, a gradual decrease of the relative concentration of F-actin was observed. Motility increased as spermatozoa became able to fertilize. Gelsolin, phalloidin, and KI inhibited sperm motility. Gelsolin canceled sperm motility within 20 min of treatment while 0.6 M KI had immediate effects. Phalloidin diminished hyperactive sperm motility slightly. All three compounds significantly increased the relative concentration of F-actin. Latrunculins are conventional drugs that destabilize the F-actin cytoskeleton. Latrunculin A (LAT A) did not affect sperm motility; but significantly increased F-actin relative concentration. The results suggested that in guinea pig spermatozoa, randomly severing F-actin filaments inhibits flagellar motility; while end filament alteration does not. Thus, specific filament regions seem to be important for sperm motility.

In guinea pig sperm, aldolase A forms a complex with actin, WAS, and Arp2/3 that plays a role in actin polymerization

“…8); thus, their interaction depends on the polymerization state of actin. It has been reported that actin polymerization occurs during capacitation (Castellani-Ceresa et al Aldolase A has a role in actin polymerization Azamar et al 2007); we thus consider this decrease as a species specific mechanism of partial actin depolymerization. Nonetheless, we have reported the formation of a post-acrosomal cone that involves actin polymerization at the boundary of capacitation/acrosomal reaction events (Sánchez-Gutiérrez et al 2002).…”

“…7A), then their interaction was confirmed by co-immunoprecipitation assays (Figs 7B and 9C and D). Considering that sperm capacitation decreases the levels of F-actin (Sánchez-Gutiérrez et al 2002, Azamar et al 2007, we decided to evaluate the aldolase A-actin interaction levels in capacitated spermatozoa; as can be seen in Fig. 7, after 2.5 h of capacitation, the levels of F-actin were decreased (Fig.…”

“…Polymerized actin staining was performed as previously reported (Azamar et al 2007), briefly, cell suspensions were fixed and then rinsed. Cells were centrifuged at 600 g for 3 min and the pellet was resuspended in 50 mM NH 4 Cl, incubated for 10 min, rinsed once with PBS, and permeabilized with 0.05% Tween-20 in PBS during 7 min.…”

“…For instance, actin polymerization is important for sperm motility during maturation (Lin et al 2002). Interestingly, maturation and motility acquisition correlate with a decrease in polymerized actin (F-actin) levels (Azamar et al 2007), whereas fertilization is impaired upon blockade of actin polymerization (Sánchez-Gutiérrez et al 2002). Recent data have shown that besides its essential role in glycolysis, aldolase participates in many other important processes: disruption of the binding capability of aldolase to B subunit of the V-ATPase, without modification of its enzymatic activity, induces V-ATPase disassembly and malfunction (Lu et al 2007); phospholipase D2 is inhibited upon the binding of aldolase to its PH domain (Kim et al 2002), thus regulating the production of lipid second messengers and associated signal pathways; a portion of aldolase interacts with F-actin in vivo (Arnold & Pette 1968, Wang et al 1997) and modulates actin polymerization in vitro (Schindler et al 2001); therefore, opening the possibility of aldolase could regulate actin dynamics in vivo.…”

Functional identity of the Gamma Tropomyosin gene

“…While microtubules are the major cytoskeletal component driving sperm motility via the motile force generation of the sperm flagellum, the actin cytoskeleton has been shown to be equally critical for sperm motility. 37,38 Both actin filament destabilizing drugs and changes in the expression of endogenous actin associated proteins impairs sperm motility. Although some of the results from these studies are contradictory, possibly due to species differences or differences in experimental conditions-the actin filament destabilizing drug cytochalasin D inhibits sperm motility in macaque sperm, 38 but not in guinea pig sperm, 37 -the results provide strong evidence for the involvement of actin filament stability and dynamics in sperm motility.…”