title: Role of Ion Channels in the Sperm Acrosome Reaction.
abstract: The acrosome reaction (AR) is a unique exocytotic process where the acrosome, a single membrane-delimited specialized organelle, overlying the nucleus in the sperm head of many species, fuses with the overlying plasma membrane. This reaction, triggered by physiological inducers from the female gamete, its vicinity, or other stimuli, discharges the acrosomal content modifying the plasma membrane, incorporating the inner acrosomal membrane, and exposing it to the extracellular medium. The AR is essential for sperm-egg coat penetration, fusion with the eggs' plasma membrane, and fertilization. As in most exocytotic processes Ca(2+) is crucial for the AR, as well as intracellular pH and membrane potential changes. Thus, among the required processes needed for this reaction, ion permeability changes involving channels are pivotal. In spite of the key role ion channels play in the AR, their identity and regulation is not fully understood. Though molecular and pharmacological evidence indicates that various ionic channels participate during the AR, such as store-operated Ca(2+) channels and voltage-dependent Ca(2+) channels, whole cell patch clamp recordings have failed to detect some of them until now. Since sperm display a very high resistance and a minute cytoplasmic volume, very few channels are needed to achieve large membrane potential and concentration changes. Functional detection of few channels in the morphologically complex and tiny sperm poses technical problems, especially when their conductance is very small, as in the case of SOCs. Single channel recordings and novel fluorescence microscopy strategies will help to define the participation of ionic channels in the intertwined signaling network that orchestrates the AR.
authors.affiliation: Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad # 2001. Col. Chamilpa., Cuernavaca Morelos, CP, 62210, Mexico.
authors.forename: Carmen
authors.initials: C
authors.lastname: Beltrán
authors.affiliation: Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad # 2001. Col. Chamilpa., Cuernavaca Morelos, CP, 62210, Mexico.
authors.forename: Claudia L
authors.initials: CL
authors.lastname: Treviño
authors.affiliation: Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad # 2001. Col. Chamilpa., Cuernavaca Morelos, CP, 62210, Mexico.
authors.forename: Esperanza
authors.initials: E
authors.lastname: Mata-Martínez
authors.affiliation: Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad # 2001. Col. Chamilpa., Cuernavaca Morelos, CP, 62210, Mexico.
authors.forename: Julio C
authors.initials: JC
authors.lastname: Chávez
authors.affiliation: Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad # 2001. Col. Chamilpa., Cuernavaca Morelos, CP, 62210, Mexico.
authors.forename: Claudia
authors.initials: C
authors.lastname: Sánchez-Cárdenas
authors.affiliation: School of Environmental and Life Science, University of Newcastle, Callaghan, 2308, NSW, Australia.
authors.forename: Mark
authors.initials: M
authors.lastname: Baker
authors.affiliation: Departamento de Genética del Desarrollo y Fisiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad # 2001. Col. Chamilpa., Cuernavaca Morelos, CP, 62210, Mexico. darszon@ibt.unam.mx.
authors.forename: Alberto
authors.initials: A
authors.lastname: Darszon
mesh_terms: D000177:Acrosome / Q000378:metabolism*; D020101:Acrosome Reaction / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism*; D005089:Exocytosis / Q000502:physiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000502:physiology*; D008297:Male; D008564:Membrane Potentials / Q000502:physiology*; D051379:Mice; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000378:metabolism
chemical_list: D015220:Calcium Channels; C488642:Catsper1 protein, mouse; C110627:Kcnu1 protein, mouse; D051036:Large-Conductance Calcium-Activated Potassium Channels; D011188:Potassium; D002118:Calcium