Incorporation and fate of specific sperm plasma membrane components following insemination as revealed by ultrastructural immunocytochemistry

Abstract

Studies have been carried out to 1) further characterize sperm specific plasma membrane polypeptides (33 and 35 kDa) that are recognized by a monoclonal antibody previously described (Longo, 1989) and 2) follow the incorporation and dispersal of these proteins within plasmalemmae of monospermic and polyspermic sea urchin (Arbacia punctulata) eggs and oocytes utilizing immunocytochemical methods at the ultrastructural level of observation. Only sperm labeled when incubated with monoclonal antibody to the 33 and 35 kDa proteins followed by colloidal gold-tagged second antibody. Colloidal gold label was observed on the egg plasma membrane immediately after gamete membrane fusion; the amount and extent of label, i.e., the distance from the site of sperm incorporation, increased with time postinsemination. By 20 min postinsemination approximately one hemisphere of the inseminated egg/oocyte was associated with label. The expanding distribution of colloidal gold label on inseminated eggs and oocytes vs. time reflects the free diffusion of 33 and 35 kDa sperm surface proteins among egg/oocyte plasma membrane components. Label was also found in forming endocytotic vesicles, suggesting that sperm plasma membrane proteins may be internalized.

Aggregation of maternal pigment granules is induced by the cytosolic discoidin domain of theXenopus Del1 protein

“…These intracellular pathogens probably use bona fide protein internalization pathways of their hosts (Ross et al, 2002). Such functional internalization is described for iron absorption (Simovich et al, 2002), signal transduction (Feng et al, 1996;Albert et al, 1998;Haversen et al, 2002;Schubert et al, 2004;Suzuki et al, 2004), and relevantly, fertilization (Longo, 1989;Parrington et al, 1996). Moreover, a combination of conserved RGD and nuclear localization signal (NLS) is found in 4G2 protein.…”