Stimulation by n6-cyclopentyladenosine of A1 adenosine receptors, coupled to galphai2 protein subunit, has a capacitative effect on human spermatozoa.
The effects of selective A(1) receptor agonist on human spermatozoa were examined to verify physiological responses and to investigate the signal transduction pathway. N6-Cyclopentyladenosine on uncapacitated spermatozoa did not induce spontaneous acrosome reaction after 5 h capacitation, whereas the number of capacitated spermatozoa, assessed by lysophosphatidylcholine-induced acrosome reaction with Pisum sativum agglutinin staining, was significantly increased. N6-Cyclopentyladenosine was also added to capacitated human spermatozoa to find out whether the agonist could induce the acrosome reaction. Results, although statistically significant, could not be considered biologically significant. A1-Mediated capacitation was followed by the increase of tyrosine phosphorylation of a protein subset ranging between M(r) = 200 000 and 30 000. Stimulation of A1 receptor with the selective agonist elicited an agonist-induced inositol phospholipid hydrolysis leading to a transient rise of inositol triphosphate (IP3). This increase was not induced by A(1) receptor antagonist and was blocked by phospholipase C inhibitor. Coimmunoprecipitation experiments showed that the A(1) receptor is coupled to Galphai2 subunit suggesting that the activation of phospholipase C is mediated by betagamma subunits. In conclusion, the A(1) adenosine receptor in human spermatozoa is coupled to Galphai2, signals via IP3, and affects the capacitative status of ejaculated spermatozoa.
Allegrucci
C
C
Dipartimento di Scienze Biochimiche e Biotecnologie Molecolari, Sezione Biochimica Cellulare, Università degli Studi di Perugia, 06126 Perugia, Italia.
Liguori
L
L
Minelli
A
A
D020101:Acrosome Reaction / Q000187:drug effects; D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000502:physiology*; D006801:Humans; D007163:Immunosorbent Techniques; D007295:Inositol Phosphates / Q000378:metabolism; D008297:Male; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D011760:Pyrrolidinones / Q000494:pharmacology; D018047:Receptors, Purinergic P1 / Q000187:drug effects* / Q000502:physiology*; D012710:Serum Albumin, Bovine / Q000494:pharmacology; D013075:Sperm Capacitation / Q000187:drug effects*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors
D004791:Enzyme Inhibitors; D004963:Estrenes; D007295:Inositol Phosphates; D010750:Phosphoproteins; D011518:Proto-Oncogene Proteins; D011760:Pyrrolidinones; D018047:Receptors, Purinergic P1; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D019000:Phosphotyrosine; D012710:Serum Albumin, Bovine; C048599:N(6)-cyclopentyladenosine; D010738:Type C Phospholipases; C498015:GNAI2 protein, human; D051960:GTP-Binding Protein alpha Subunit, Gi2; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D000241:Adenosine