FPP modulates mammalian sperm function via TCP-11 and the adenylyl cyclase/cAMP pathway.
Fertilization promoting peptide (FPP; pGlu-Glu-ProNH2), which is found in seminal plasma, promotes capacitation but inhibits spontaneous acrosome loss in mammalian spermatozoa in vitro. Adenosine, known to modulate the adenylyl cyclase (AC)/cAMP pathway, elicits these same responses whereas FPP + adenosine produces an enhanced response, leading to the hypothesis that FPP and adenosine modulate the same signal transduction pathway but act via different receptors. TCP-11, the product of a t-complex gene, is the putative receptor for FPP: Fab fragments of anti-TCP-11 antibodies have the same effect as FPP on mouse spermatozoa and Gln-FPP, a competitive inhibitor of FPP, also competitively inhibits responses to the Fab fragments. In the present study, specific binding of 3H-FPP to sperm membranes was significantly inhibited by 200 nM Gln-FPP and anti-TCP-11 Fab fragments (1/25 dilution), thus confirming that FPP, Gln-FPP, and Fab fragments compete for the same binding site. In addition, spermatozoa treated with A23187 to induce the acrosome reaction bound significantly less 3H-FPP than untreated cells, suggesting that a large proportion of the FPP binding sites are associated with the acrosomal cap region; TCP-11 is located in this region. In other experiments, 100 nM FPP significantly stimulated cAMP production in mouse sperm membranes, permeabilized cells and intact cells. Furthermore, Gln-FPP inhibited production of cAMP in response to FPP but not to adenosine (10 microM) or its analogue NECA (100 nM), supporting the involvement of two different receptors. Finally, anti-TCP-11 Fab fragments (1/25 dilution) significantly stimulated cAMP production, whereas low Fab (1/200; nonstimulatory when used alone) plus adenosine (10 microM) significantly enhanced the stimulation of capacitation by adenosine. These results support the hypotheses that TCP-11 is the receptor for FPP and that FPP<-->TCP-11 interactions modulate AC/cAMP.
Adeoya-Osiguwa
S A
SA
Anatomy and Human Biology, King's College London, Strand, United Kingdom.
Dudley
R K
RK
Hosseini
R
R
Fraser
L R
LR
D000241:Adenosine / Q000494:pharmacology; D019830:Adenosine-5'-(N-ethylcarboxamide) / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D018833:Chaperonins / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism; D007140:Immunoglobulin Fab Fragments / Q000276:immunology; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D008565:Membrane Proteins; D051379:Mice; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins / Q000276:immunology / Q000378:metabolism*; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D013094:Spermatozoa / Q000187:drug effects*; D013735:Testicular Hormones / Q000378:metabolism; D013973:Thyrotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology; D044767:Ubiquitin-Protein Ligases; D056427:t-Complex Genome Region
D004268:DNA-Binding Proteins; D007140:Immunoglobulin Fab Fragments; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; C533399:TCP11 protein, human; C533400:Tcp11 protein, mouse; D013735:Testicular Hormones; C116889:glutaminyl-pyroglutamyl-glutamyl-proline amide; D019830:Adenosine-5'-(N-ethylcarboxamide); D013973:Thyrotropin-Releasing Hormone; C059697:pyroglutamyl-glutamyl-proline amide; D000242:Cyclic AMP; C116196:PPP1R11 protein, human; D044767:Ubiquitin-Protein Ligases; D018833:Chaperonins; D000262:Adenylyl Cyclases; D000241:Adenosine; D011761:Pyrrolidonecarboxylic Acid