Role of protein tyrosine phosphorylation in the thapsigargin-induced intracellular Ca(2+) store depletion during human sperm acrosome reaction.
During human sperm capacitation, an increase in phosphotyrosine content of specific proteins results partially from an increase in the intracellular free Ca(2+) concentrations. In the present study, the inter-regulation between protein phosphotyrosine content and the intracellular Ca(2+) concentration during the thapsigargin treatment of capacitated human sperm was investigated. The involvement of a tyrosine kinase pathway in the thapsigargin-induced acrosome reaction was also investigated. In response to thapsigargin, two sperm subpopulations, called LR (low responsive) and HR (high responsive), according to their increase in intracellular Ca(2+), were observed. In addition to their high increase in intracellular Ca(2+), sperm from the HR population expressed a higher protein phosphotyrosine content, and a higher proportion (P < 0.05) of them underwent the acrosome reaction in response to thapsigargin, as compared with LR sperm. Although the tyrosine kinase inhibitor PP2 abolished the thapsigargin-induced increase in protein phosphotyrosine content, it did not affect the intracellular Ca( 2+) concentration or the percentage of acrosome-reacted sperm. The inability of an src-related tyrosine kinase inhibitor to block the thapsigargin-mediated Ca(2+) increase and acrosomal exocytosis suggests that, during the acrosome reaction, the signalling pathway mediated by src-related tyrosine kinases is involved upstream of the capacitative Ca(2+) entry.
Dorval
Véronique
V
Département d'Obstétrique/Gynécologie and Centre de recherche en Biologie de la Reproduction, Université Laval, Québec, G1L 3L5.
Dufour
Maurice
M
Leclerc
Pierre
P
D020101:Acrosome Reaction; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000378:metabolism*; D006801:Humans; D008297:Male; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D013075:Sperm Capacitation / Q000502:physiology; D013094:Spermatozoa / Q000378:metabolism*; D019284:Thapsigargin / Q000378:metabolism*
D004791:Enzyme Inhibitors; D019284:Thapsigargin; D011505:Protein-Tyrosine Kinases; D002118:Calcium