title: Rho-kinase (ROCK) in sea urchin sperm: its role in regulating the intracellular pH during the acrosome reaction.
abstract: Sperm must undergo the acrosome reaction (AR) in order to fertilize the egg. In sea urchins, this reaction is triggered by the egg jelly (EJ) which, upon binding to its sperm receptor, induces increases in the ion permeability of the plasma membrane and changes in protein phosphorylation. Here, we demonstrated that the sperm expresses ROCK (approximately 135kDa), which is a serine/threonine protein kinase. ROCK localized, as RhoGTPase (Rho), in the acrosomal region, midpiece and flagellum. H-1152, a ROCK antagonist, inhibited the two cellular processes defining the AR: the acrosomal exocytosis and the actin polymerization. The ionophores nigericin and A23187 reversed the AR inhibition induced by H-1152, suggesting that ROCK functions at the level of the EJ-induced ion fluxes. Accordingly, H-1152 blocked 70% the intracellular alkalinization induced by EJ. These results indicate that EJ activates a Na+-H+ exchanger (NHE) in the sperm through a Rho/ROCK-dependent signaling pathway that culminates in the AR.
authors.affiliation: Instituto de Investigación en Biología Experimental, Facultad de Química, Universidad de Guanajuato, Guanajuato 36050, Mexico.
authors.forename: Citlali Urióstegui
authors.initials: CU
authors.lastname: de la Sancha
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Martínez-Cadena
authors.forename: Juana
authors.initials: J
authors.lastname: López-Godínez
authors.forename: Laura E
authors.initials: LE
authors.lastname: Castellano
authors.forename: Takuya
authors.initials: T
authors.lastname: Nishigaki
authors.forename: Takuya
authors.initials: T
authors.lastname: Nishisaki
authors.forename: Alberto
authors.initials: A
authors.lastname: Darszon
authors.forename: Jesús
authors.initials: J
authors.lastname: García-Soto
mesh_terms: D020101:Acrosome Reaction / Q000502:physiology*; D000818:Animals; D002478:Cells, Cultured; D006706:Homeostasis / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D008297:Male; D012617:Sea Urchins / Q000378:metabolism*; D013094:Spermatozoa / Q000502:physiology*; D054460:rho-Associated Kinases / Q000737:chemistry / Q000378:metabolism*
chemical_list: D054460:rho-Associated Kinases