Particulate adenylate cyclase plays a key role in human sperm olfactory receptor-mediated chemotaxis.
Human sperm chemotaxis is a critical component of the fertilization process, but the molecular basis for this behavior remains unclear. Recent evidence shows that chemotactic responses depend on activation of the sperm olfactory receptor, hOR17-4. Certain floral scents, including bourgeonal, activate hOR17-4, trigger pronounced Ca(2+) fluxes, and evoke chemotaxis. Here, we provide evidence that hOR17-4 activation is coupled to a cAMP-mediated signaling cascade. Multidimensional protein identification technology was used to identify potential components of a G-protein-coupled cAMP transduction pathway in human sperm. These products included various membrane-associated adenylate cyclase (mAC) isoforms and the G(olf)-subunit. Using immunocytochemistry, specific mAC isoforms were localized to particular cell regions. Whereas mAC III occurred in the sperm head and midpiece, mAC VIII was distributed predominantly in the flagellum. In contrast, G(olf) was found mostly in the flagellum and midpiece. The observed spatial distribution patterns largely correspond to the spatiotemporal character of hOR17-4-induced Ca(2+) changes. Behavioral and Ca(2+) signaling responses of human sperm to bourgeonal were bioassayed in the presence, or absence, of the adenylate cyclase antagonist SQ22536. This specific agent inhibits particulate AC, but not soluble AC, activation. Upon incubation with SQ22536, cells ceased to exhibit Ca(2+) signaling, chemotaxis, and hyperactivation (faster swim speed and flagellar beat rate) in response to bourgeonal. Particulate AC is therefore required for induction of hOR17-4-mediated human sperm behavior and represents a promising target for future design of contraceptive drugs.
Department of Anatomy and Neurobiology, University of Maryland, Baltimore, Maryland 21201, USA. mspeh001@umaryland.edu
Marc
M
Spehr
Katlen
K
Schwane
Jeffrey A
JA
Riffell
Jon
J
Barbour
Richard K
RK
Zimmer
Eva M
EM
Neuhaus
Hanns
H
Hatt
D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism*; D020013:Calcium Signaling / Q000502:physiology; D002633:Chemotaxis / Q000502:physiology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005407:Flagella / Q000502:physiology; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000378:metabolism; D006801:Humans; D008297:Male; D018035:Receptors, Odorant / Q000378:metabolism*; D029589:Seminal Plasma Proteins / Q000378:metabolism*; D013077:Sperm Head / Q000378:metabolism; D032961:Sperm Midpiece / Q000378:metabolism*; D013081:Sperm Motility / Q000502:physiology*
D000067956:Adenylyl Cyclase Inhibitors; D004791:Enzyme Inhibitors; C473192:OR1D2 protein, human; D018035:Receptors, Odorant; D029589:Seminal Plasma Proteins; C017759:9-(tetrahydro-2-furyl)-adenine; D019205:GTP-Binding Protein alpha Subunits, Gs; D000262:Adenylyl Cyclases; D000225:Adenine