Biochemical characterization of integral membrane heparan sulfate proteoglycans in Sertoli cells from immature rat testis

S-35-Radiolabeled cultured Sertoli cells from immature rat testis were extr acted with detergent and the different proteoheparan sulfate (HSPG) forms o f the extract were discriminated and quantified on the basis of their high anionic charge, hydrodynamic size, lipophilic properties, susceptibility to trypsin and phosphatidylinositol phospholipase C (PI-PLC). Trypsin release d 50% of total cellular HSPG corresponding to 80% of total hydrophobic HSPG . Trypsin-accessible HSPG were presumed to be integral membrane species. Tr ypsin-resistant HSPG, probably intracellular, distributed into non-lipophil ic (37.5%) and lipophilic (12.5%) populations. Biochemical analysis of pc c opurified with plasma membrane confirmed the existence of hydrophobic HSPG integrated into this structure. Among hydrophobic HSPG accessible to trypsi n, 35% were PI-PLC released and radiolabeled by [H-3]inositol indicating th at about one third of integral membrane HSPG were intercalated into the pla sma membrane through a phosphatidylinositol anchor (glypican type). PI-PLC- resistant forms represented HSPG inserted into the membrane through a hydro phobic segment of the core protein (syndecan type). No lipophilic PG was pr esent in other cell compartments (culture medium, cell periphery, extracell ular matrix)I-125-Iodinated hydrophobic HSPG were deglycanated and submitte d to SDS-polyacrylamide gel electrophoresis. In the glypican family, a core protein (64-65 kDa) was detected, whereas in the syndecan family, bands of 60 and 68 kDa were observed which may correspond to self-association of di fferent core proteins. In Sertoli cell, specific functional attributes of d ifferent integral membrane HSPG forms remain to be investigated. (C) 2001 E lsevier Science B.V. All rights reserved.