Research in this three-times revised proposal is aimed at understanding the molecular steps involved in the initiation of the human sperm acrosome reaction. Progesterone secreted by follicular cells of the cumulus oophorus, is regarded as an in vivo acrosome reaction initiator by interacting with sperm membrane receptors to trigger an influx of Ca2+ and an efflux of Cl-. In addition, progesterone or a 3a-OH progesterone metabolite may bind or activate a unique human sperm GABAA-like receptor Cl- channel as well as bind to a receptor for a Ca2+ channel. The possibility exists that progesterone binds to one receptor/channel site and then activate the other receptor/channel by cross-talk. The application includes a series of studies concerned with the receptors, channels and ionic interactions through which progesterone initiates the human sperm acrosome reaction. The proposed specific aims will determine first whether a sperm GABAA-like receptor/Cl- channel is involved in progesterone-mediated Cl- efflux by using pharmacological agents which will determine differences between sperm and neuronal GABAA-like receptor/Cl-channels.
A second aim i s to determine which region of the sperm head the progesterone-mediated cytosolic Cl- efflux through the steroid receptor/Cl-channel begins during acrosome reaction.
A third aim i s to use available monoclonal antibodies against domains of the intracellular progesterone receptor and neuronal GABAA-like receptor/Cl- channel subunits to identify and further characterize the human sperm progesterone receptor(s).
A fourth aim i s to compare the effect of progesterone stereo isomers on Cl- and Ca2- flux to determine whether two separate progesterone receptors operate to elicit ion fluxes. A fifth aim is to determine whether human sperm can convert progesterone into an 3a-hydroxy metabolite known to activate neuronal GABAA-like receptor/Cl- channels and able to initiate the human acrosome reaction. A sixth aim is to determine whether Cl- efflux mediated by the GABAA-like receptor/Cl- channel controls progesterone-mediated Ca2+ influx. Finally, a seventh aim will use immunoelectron microscopy to determine the distribution of the human progesterone receptor(s) and human sperm GABAA-like receptor/Cl- channel at a high resolution level.

Agency
National Institute of Health (NIH)
Institute
Eunice Kennedy Shriver National Institute of Child Health & Human Development (NICHD)
Type
Research Project (R01)
Project #
5R01HD023098-08
Application #
2888944
Study Section
Reproductive Biology Study Section (REB)
Program Officer
Rankin, Tracy L
Project Start
1997-07-01
Project End
2002-06-30
Budget Start
1999-07-01
Budget End
2002-06-30
Support Year
8
Fiscal Year
1999
Total Cost
Indirect Cost
Name
University of California Davis
Department
Anatomy/Cell Biology
Type
Schools of Medicine
DUNS #
094878337
City
Davis
State
CA
Country
United States
Zip Code
95618
Bray, Christopher; Son, Jung-Ho; Meizel, Stanley (2002) A nicotinic acetylcholine receptor is involved in the arosome reaction of human sperm initiated by recombinant human ZP3. Biol Reprod 67:782-8
Harrison, D A; Carr, D W; Meizel, S (2000) Involvement of protein kinase A and A kinase anchoring protein in the progesterone-initiated human sperm acrosome reaction. Biol Reprod 62:811-20
Buddhikot, M; Falkenstein, E; Wehling, M et al. (1999) Recognition of a human sperm surface protein involved in the progesterone-initiated acrosome reaction by antisera against an endomembrane progesterone binding protein from porcine liver. Mol Cell Endocrinol 158:187-93
Garcia, M A; Meizel, S (1999) Progesterone-mediated calcium influx and acrosome reaction of human spermatozoa: pharmacological investigation of T-type calcium channels. Biol Reprod 60:102-9
Garcia, M A; Meizel, S (1999) Determination of the steady-state intracellular chloride concentration in capacitated human spermatozoa. J Androl 20:88-93
Garcia, M A; Meizel, S (1999) Regulation of intracellular pH in capacitated human spermatozoa by a Na+/H+ exchanger. Mol Reprod Dev 52:189-95
Falkenstein, E; Heck, M; Gerdes, D et al. (1999) Specific progesterone binding to a membrane protein and related nongenomic effects on Ca2+-fluxes in sperm. Endocrinology 140:5999-6002
Meizel, S (1997) Amino acid neurotransmitter receptor/chloride channels of mammalian sperm and the acrosome reaction. Biol Reprod 56:569-74
Turner, K O; Syvanen, M; Meizel, S (1997) The human acrosome reaction is highly sensitive to inhibition by cyclodiene insecticides. J Androl 18:571-5
Meizel, S; Turner, K O; Nuccitelli, R (1997) Progesterone triggers a wave of increased free calcium during the human sperm acrosome reaction. Dev Biol 182:67-75

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