Membrane associated proteoglycans in rat testicular peritubular cells

Abstract

Confluent testicular peritubular cells derived from immature rats were used to study membrane associated proteoglycans (PG). Peripheral material (heparin releasable), membrane and intracellular material (Triton X-100 releasable) were collected, purified by anion exchange chromatography then characterized by gel filtration and by hydrophobic interaction chromatography, followed by enzymatic digestion and chemical treatment. The peripheral material was constituted of two populations of PG (Kav = 0 and 0.10 on Superose 6 column), each containing both heparan sulfate proteoglycans (HSPG) and chondroitin proteoglycans (CSPG) and perhaps a hybrid PG (HSCSPG). These PG being not retained on an octyl Sepharose column, they were devoided of hydrophobic properties. The integral membrane proteoglycans isolated on the basis of their hydrophobic properties represented 20% of the Triton X-100 releasable material, and were exclusively constituted of proteoheparan sulfate. There were no relationships between this membrane HSPG and the peripheral HSPG as evidenced by pulse chase experiments. The mode of intercalation of the hydrophobic HSPG in the cell membrane was studied. The majority of these macromolecules (80%) were sensitive to trypsin and only a minor proportion (20%) were sensitive to phosphatidylinositol specific phospholipase C. Thus, about 80% of the hydrophobic HSPG were intercalated in the cell membrane by a hydrophobic segment of the core protein whereas about 20% were associated with the cell membrane via a phosphatidylinositol residue covalently bound to the core protein of the PG.

Precocious initiation of spermatogenesis in a 19-month-old boy with Hurler syndrome

“…A local effect induced by the heparane sulphate accumulation is also possible. Indeed, the proteoglycans are present in the seminiferous tubule basement membrane [37] and in the membrane of Sertoli cells [38]. The function of the proteoglycans remains to be cleared up, but we know, for example, that spermatogonia and Sertoli cells require follistatin to modulate the actions of activin A during the development of the testicle [39] and that the active form of follistatin binds to the cell surfaces or the basement membranes with a strong affinity for proteoglycans [40].…”

Inhibition of transmembrane calcium influx induces decrease in proteoglycan synthesis in immature rat sertoli cells

“…In the rat testis, the cell types located on both sides of the basement membrane surrounding seminiferous tubules, namely peritubular cells and Sertoli cells, synthesize HSPG and CSPG [Skinner and Fritz, 1985;Mounis et al, 1991;Bichoualne et al, 1994]. PG synthesis has also been observed in interstitial Leydig cells [Grudet et al, 1996].…”