Protein kinase C plays an important role in the human zona pellucida- induced acrosome reaction

Abstract

To investigate the involvement of protein kinases in signal transduction in the human zona pellucida (ZP)-induced acrosome reaction (AR), the effects of protein kinase (PK) activators, dibutyryl cAMP (PKA) and cGMP (PKG), phorbol 12-myristate 13-acetate (PMA, PKC), and the PKC inhibitor, staurosporine were studied. Sperm samples were obtained from normozoospermic men with normal sperm-ZP binding. Oocytes were obtained from other patients with failure of fertilization in vitro. Motile spermatozoa selected by a swim-up technique were pre-incubated with 2.5-20 microM PMA, 1 mM dibutyryl cAMP or cGMP, 3 mM pentoxifylline or 0.125-2.0 microM staurosporine for 30 min and then incubated with four oocytes for 2 h in human tubal fluid supplemented with bovine serum albumin. The spermatozoa bound to the ZP were dislodged by repeatedly aspirating the oocytes with a small bore pipette and the state of the AR was determined by fluorescein-labelled Pisum sativum agglutinin. Motility and movement characteristics were assessed by computer-assisted sperm analysis (CASA) after incubation of spermatozoa with PMA for 30 min and 2 h. The dibutyryl cAMP and cGMP analogues had a small positive effect (P < 0.05) but pentoxifylline had no effect on stimulating the ZP-induced AR (P > 0.05). In contrast, PMA stimulated ZP-induced AR in a marked dose-dependent manner. Only the highest concentrations (15-20 microM) of PMA significantly decreased percentage motility (P < 0.001). Doses of 2.5-15 microM of PMA significantly stimulated ZP-induced AR without decreasing motility (P < 0.001). The PKC inhibitor, staurosporine (0.125-0.25 microM) significantly inhibited ZP-induced AR without affecting motility (P < 0.001). Sperm samples from 33 normozoospermic men were used for studies of the ZP-induced AR augmented with 15 microM PMA. One sample did not show a response to PMA stimulation. Among the 14 men with low ZP-induced AR, half had normal responses to PMA and other half had low responses to PMA. In conclusion, activation or inhibition of PKC significantly increases or decreases human ZP-induced AR suggesting that PKC plays a important role in the signal transduction pathway for the physiological AR.

Relationship between seminal plasma zinc concentration and spermatozoa–zona pellucida binding and the ZP-induced acrosome reaction in subfertile men

“…In severe teratozoospermic subfertile men, defective ZPIAR is more likely to be related to major structural defects of the sperm head, such as small or abnormal acrosomes, or associated abnormalities in the overlying plasma membrane. By contrast, in men with normal sperm morphology, defective ZPIAR is most likely to be due to subtle biochemical or molecular defects in ZP receptors, signal transduction pathways, inefficient cholesterol or zinc removal from the plasma membrane during capacitation, actin polymerization or acrosomal enzyme activation [36][37][38][39][40][41][42]. Several in vitro studies have shown that zinc and SP inhibit sperm capacitation, including hyperactivation and AR, as well as spermatozoa-ZP binding and penetration [17,[20][21][22].…”

Localization of Guanylate Cyclase Receptor, Inositol Trisphosphate Receptor, and Calmodulin in Boar Spermatozoa

“…Close association of IP 3 R and GCR in sperm membrane supports the suggestion made by Suarez and coworkers that IP3 mediated release of Ca 2+ from calmodulin stores is related to the control of gated calcium channels during sperm motility and hyperactivated motility Suarez, 2001, 2003). These processes may also be operational during fusion of sperm with oocyte membranes at the time of fertilization (Liu andBarker 1997, Revelli et al, 2002). The role of GC is well defined and several studies confirm that GC regulates not only the gated Ca 2+ channel but it also plays an important role as a chemotactic agent during sperm oocyte fusion in sea urchin (Santos-Sacchi and Gordon 1980, , Cohen-Dayag et al, 1995.…”

PKC Regulation of Gametogenesis and Early Development

“…In addition, some have shown that components of the egg zona pellucida are responsible for the acrosome reaction, but similarly the older drug inhibitor of PKC, Staurosporine, blocks the acrosome reaction (Liu and Baker, 1997).…”