Identification of spermatogenic cell plasma membrane glycoproteins by two-dimensional electrophoresis and lectin...

Plasma membrane glycoproteins present in purified mouse spermatogenic cells have been identified by two-dimensional polyacrylamide gel electrophoresis and lectin blotting techniques. Four membrane glycoproteins labelled with Bandeiraea simplicifolia lectin (I) have been detected, ranging in Mr from 55 000 to 76 000 and in pI from 6.0 to 6.3. Only one of these proteins, p76/6.3, is synthesized by short-term in vitro cultures of spermatogenic cells, as determined by the incorporation of [35S]methionine. Approximately 20 surface glycoproteins labelled with concanavalin A have been identified, ranging in Mr from 50 000 to 151 000 and in pI from 5.7 to 7.0. None of the components detected with B. simplicifolia lectin (I) are labelled significantly with concanavalin A. A major concanavalin A-binding protein in the membranes of both pachytene spermatocytes and round spermatids is p151/6.0. This glycoprotein has been previously shown to be exposed on the outer surface of spermatogenic cell membranes and may represent a mediator of germ cell-Sertoli cell interactions. Furthermore, two constituents identified in the present study represent stage-specific markers. Component p73/5.7 is detected with concanavalin A only in the membranes of pachytene spermatocytes. Conversely, p84/6.3 is found only in round spermatid membranes. These results, then have: (a) provided a map of membrane glycoproteins in developing mouse male germ cells; (b) identified p151/6.0 as a membrane constituent of possible functional significance; and (c) identified the first reported glycoprotein surface differentiation markers for mouse spermatogenesis.