REARRANGEMENT OF THE PH-20 PROTEIN ON THE SURFACE OF MACAQUE SPERMATOZOA FOLLOWING EXPOSURE TO ANTI-PH-20 ANTIBODIES OR BINDING TO ZONA-PELLUCIDA

Capacitated cynomolgus macaque sperm have a surface hyaluronidase (PH- 20) that is evenly distributed over the entire head and can be visuali zed at the ultrastructural level using a secondary antibody labeled wi th colloidal gold. Exposure of sperm to mono-specific, bivalent polycl onal antibodies to PH-20 causes a rapid clustering of PH-20. The predo minant morphological consequence of PH-20 redistribution is its aggreg ation along the lateral edge of the sperm head. Monovalent Fab fragmen ts of the anti-PH-20 antibody bound to the sperm head but did not indu ce a change in PH-20 distribution. PH-20 aggregation was observed in a lmost all sperm following treatment with the polyclonal antibody, but only about 20% of the sperm had morphological acrosome reactions, rega rdless of the time of exposure or the concentration of antibody. There was morphological evidence of swelling of the acrosomal matrix in ove r 50% of the sperm following exposure to anti-PH-20 antibodies. Anti-P H-20 Fab fragments did not induce the acrosome reaction or acrosomal m atrix swelling. Sperm bound to macaque zona pellucida also showed aggr egation of the PH-20 protein as soon as 30 sec after sperm-zona intera ction. This aggregation was not observed when macaque sperm were bound to hamster zona pellucida. When macaque sperm were surface-labeled wi th biotin and then incubated with anti-PH-20 antibodies or macaque zon a pellucida, there was no evidence of a global surface protein rearran gement, although PH-20 protein was aggregated on the surface of the sa me sperm cells. An increase in levels of internal sperm Ca++ was measu red in association with the antibody-induced PH-20 aggregation. Fab fr agments did not increase Ca++ levels, but when they were crosslinked w ith anti-fab antibody there was a significant Ca++ increase and induct ion of acrosome reactions. Anti-PH-20 Fab fragments did not block maca que sperm binding to macaque zona pellucida or the zona-induced acroso me reaction. We conclude that PH-20 on the sperm surface is involved i n sperm-zona pellucida interaction and the zona-induced acrosome react ion. (C) 1998 Wiley-iiss, Inc.