Role of Wasp and the small GTPases RhoA, RhoB, and Cdc42 during capacitation and acrosome reaction in spermatozoa of English guinea pigs

Abstract

Cytoskeleton remodeling is necessary for capacitation and the acrosome reaction in spermatozoa. F-actin is located in the acrosome and equatorial region during capacitation, but is relocated in the post-acrosomal region during the acrosome reaction in spermatozoa from bull, rat, mice, and guinea pig. Actin polymerization and relocalization are generally regulated by small GTPases that activate Wasp protein, which coordinates with Arp2/3, profilin I, and profilin II to complete cytoskeletal remodeling. This sequence of events is not completely described in spermatozoa, though. Therefore, the aim of this study was to determine if Wasp interacts with small GTPases (RhoA, RhoB, and Cdc42) and proteins (Arp2/3, profilin I, and profilin II) that co-localize with F-actin during capacitation and the acrosome reaction in English guinea pig spermatozoa obtained from the vas deferens. The spermatozoa were capacitated in calcium-free medium, incubated with an activator or an inhibitor of GTPases, and then induced to acrosome react using calcium. The distribution patterns of F-actin were compared to the patterns of Wasp and its putative interaction partners: Wasp and RhoB, but not RhoA or Cdc42, localization overlap with F-actin during capacitation and the acrosome reaction. Activation of small GTPases localized RhoB to the post-acrosomal region whereas their inhibition prevented acrosome exocytosis. Arp2/3 and profilin II appear to interact with Wasp in the post-acrosomal region and flagellum, while profilin I and Wasp could be found in the equatorial region. Thus, Wasp and F-actin distribution overlap during capacitation and acrosome reaction, and small GTPases play an important role in cytoskeleton remodeling during these processes in spermatozoa. Mol. Reprod. Dev. 83: 927-937, 2016 © 2016 Wiley Periodicals, Inc.

Rac1 is necessary for capacitation and acrosome reaction in guinea pig spermatozoa

“…It prevents the premature fusion of the membranes and forms a scaffolding of proteins required for the normal course of the AR . Although some signaling pathways that could regulate the polymerization of actin in sperm have already been reported, they have not been related to the structuring in the apical region of the acrosome of the actin cytoskeleton . Our results show that, during capacitation, an actin cytoskeleton shaped like a headband or diadem is structured in the apical region of the acrosome, a cytoskeleton that was absent when Rac1 was inhibited, and although the quantity of F‐actin in the acrosome increases, the headband‐like structure was not observed (Figure A).…”

“…13,32,33 Although some signaling pathways that could regulate the polymerization of actin in sperm have already been reported, they have not been related to the structuring in the apical region of the acrosome of the actin cytoskeleton. 21,27,32,34 Our results show that, during capacitation, an actin cytoskeleton shaped like a headband or diadem is structured in the apical region of the acrosome, a cytoskeleton that was absent when Rac1 was inhibited, and although the quantity of F-actin in the acrosome increases, the headband-like structure was not observed ( Figure 4A). Our data also indicate that the formation of this actin headband in the apical region of the acrosome can only be a consequence of the activity of Rac1.…”

“…Capacitated spermatozoa presented an increase in fluorescence, mainly in the apical region of the acrosome, the flagellum and the equatorial segment (FAP2; Figure A). These two patterns are typically observed during the capacitation of guinea pig spermatozoa . Spermatozoa capacitated in the presence of NSC23766 presented a third pattern of increased staining, but unlike FAP1 and FAP2, the increase occurred throughout the acrosome, except for the apical region (FA3P; Figure A).…”

“…These two patterns are typically observed during the capacitation of guinea pig spermatozoa. 10,12,27 Spermatozoa capacitated in the presence of NSC23766 presented a third pattern of increased staining, but unlike FAP1 and FAP2, the increase occurred throughout the acrosome, except for the apical region (FA3P; Figure 4A). The quantification of these three patterns shows a significant increase of FAP2 in capacitated spermatozoa as compared with noncapacitated spermatozoa; such increase was significantly inhibited in capacitated spermatozoa in the presence of NSC23766 ( Figure 4B).…”

Yes‐associated protein promotes cell migration via activating Wiskott‐Aldrich syndrome protein family member 1 in oral squamous cell carcinoma

“…We examined the expression levels of the WASF1 gene and found that they were downregulated following YAP knockdown compared with those noted in the control cells. WASP proteins function as downstream effectors of the Rho GTPases and comprise two distinct subfamilies, which play important roles in cytoskeletal rearrangement and actin polymerization . All WASP subfamily members share a tripartite VCA (Verprolin homology, Cofilin homology, and Acidic) domain .…”