Elucidation of the signaling pathways that underpin capacitation-associated surface phosphotyrosine expression in mouse spermatozoa.
Recent studies from within our laboratory have demonstrated a causal relationship between capacitation-associated surface phosphotyrosine expression and the ability of mouse spermatozoa to recognize the oocyte and engage in sperm-zona pellucida interaction. In the studies described herein we have sought to investigate the signaling pathways that underpin the tyrosine phosphorylation of sperm surface protein targets and validate the physiological significance of these pathways in relation to sperm-zona pellucida adhesion. Through selective pharmacological inhibition we have demonstrated that surface phosphotyrosine expression is unlikely to be mediated by the canonical cAMP-dependent protein kinase A (PKA) signaling cascade that has been most widely studied in relation to sperm capacitation. Rather, it appears to be primarily driven by the extracellular signal-regulated kinase (ERK) module of the mitogen-activated protein kinase (MAPK) pathway. Consistent with this notion, the main components of the ERK module (RAS, RAF1, MEK, and ERK1/2) were localized to the periacrosomal region of the head of mature mouse spermatozoa and their phosphorylation status within this region of the cell was positively modulated by capacitation. Furthermore, inhibition of several elements of this pathway suppressed sperm surface phosphotyrosine expression and induced a concomitant reduction sperm-zona pellucida interaction. Collectively, these data highlight a previously unappreciated role of the ERK module in the modification of the sperm surface during capacitation to render these cells functionally competent to engage in the process of fertilization.
Reproductive Science Group, School of Environmental and Life Sciences, University of Newcastle, Callaghan, Australia. brett.nixon@newcastle.edu.au
Brett
B
Nixon
Amanda
A
Bielanowicz
Amanda L
AL
Anderson
Andrew
A
Walsh
Tess
T
Hall
Andrea
A
Mccloghry
R John
RJ
Aitken
D000818:Animals; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D020930:MAP Kinase Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects; D008297:Male; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000037:antagonists & inhibitors / Q000378:metabolism; D010766:Phosphorylation; D019000:Phosphotyrosine / Q000378:metabolism*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D019908:Proto-Oncogene Proteins c-raf / Q000037:antagonists & inhibitors / Q000378:metabolism; D013075:Sperm Capacitation / Q000187:drug effects; D013084:Sperm-Ovum Interactions / Q000187:drug effects; D013094:Spermatozoa / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D013997:Time Factors; D018631:ras Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism
D047428:Protein Kinase Inhibitors; D019000:Phosphotyrosine; D019908:Proto-Oncogene Proteins c-raf; D017868:Cyclic AMP-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020930:MAP Kinase Kinase Kinases; D018631:ras Proteins