title: Involvement of an F-actin skeleton on the acrosome reaction in guinea pig spermatozoa.
abstract: The acrosome reaction (AR) is a regulated exocytotic process. In several cell types, an actin network situated under the plasma membrane (PM) acts as a physical barrier to prevent this exocytosis. In seeking a function for a cortical skeleton in guinea pig spermatozoa, the PM and the outer acrosomal membrane (OAM) were investigated for the presence of F-actin and spectrin, proteins generally found in cell cortical skeletons. Both membrane types were visualized in whole-mount preparations by electron microscopy. PM proteins gave positive reaction to the Na(+),K(+)-ATPase antibody and the OAM proteins did not react to the antibody. Furthermore, a Triton X-100-resistant skeleton was obtained from both membrane types. Using gold immunoelectron microscopy, F-actin was visualized in the PM and in the OAM skeletons, while spectrin was only detected in the PM skeleton. The presence of an F-actin cortical skeleton in the sperm PM suggests that F-actin may be involved in the AR. The significantly higher number of AR elicited by cytochalasin D (Cyt-D) treatment(P<0.005) and data showing a significant (P>0.03) decrease in F-actin relative concentration in capacitating spermatozoa, agree with this suggestion. Furthermore, the proposal is strengthened by the fact that stabilization of F-actin by phalloidin (Ph) significantly (P>0.01) diminished AR induced by Ca(2+) in a streptolysin O (SLO)-permeabilized sperm model.
authors.affiliation: Departamento de Biología Celular, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional (CINVESTAV), México D.F., México.
authors.forename: E O
authors.initials: EO
authors.lastname: Hernández-González
authors.forename: A N
authors.initials: AN
authors.lastname: Lecona-Valera
authors.forename: J
authors.initials: J
authors.lastname: Escobar-Herrera
authors.forename: A
authors.initials: A
authors.lastname: Mújica
mesh_terms: D020101:Acrosome Reaction / Q000187:drug effects / Q000502:physiology*; D000199:Actins / Q000032:analysis / Q000378:metabolism*; D000818:Animals; D001426:Bacterial Proteins; D015153:Blotting, Western; D002462:Cell Membrane / Q000737:chemistry / Q000201:enzymology / Q000648:ultrastructure; D015638:Cytochalasin D / Q000494:pharmacology; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology; D006168:Guinea Pigs; D007150:Immunohistochemistry; D008297:Male; D016253:Microscopy, Immunoelectron; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D010590:Phalloidine / Q000494:pharmacology; D011108:Polymers / Q000378:metabolism; D000254:Sodium-Potassium-Exchanging ATPase / Q000032:analysis; D013049:Spectrin / Q000032:analysis / Q000378:metabolism; D013094:Spermatozoa / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D013301:Streptolysins / Q000494:pharmacology
chemical_list: D000199:Actins; D001426:Bacterial Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D011108:Polymers; D013301:Streptolysins; C025964:streptolysin O; D013049:Spectrin; D010590:Phalloidine; D015638:Cytochalasin D; D000254:Sodium-Potassium-Exchanging ATPase