Expression and function of class B scavenger receptor type I on both apical and basolateral sides of the plasma membrane of polarized testicular Sertoli cells of the rat

Abstract

Class B scavenger receptor type I (SR-BI), a multiligand membrane protein, exists in various organs and cell types. In the testis, SR-BI is expressed in two somatic cell types: Leydig cells and Sertoli cells. Unlike interstitially localized Leydig cells, Sertoli cells present within the seminiferous tubules keep contact with spermatogenic cells and form the tight junction to divide the seminiferous epithelium into the basal and adluminal compartments. In this study, the expression and function of SR-BI in rat Sertoli cells were examined with respect to dependency on the spermatogenic cycle, the plasma membrane polarity, and the pituitary hormone follicle-stimulating hormone (FSH). When the expression of SR-BI was histochemically examined with testis sections, both protein and mRNA were already present in Sertoli cells during the first-round spermatogenesis and continued to be detectable thereafter. The level of SR-BI mRNA expression in Sertoli cells was lower at spermatogenic stages I-VI than at other stages. SR-BI was present and functional (in mediating cellular incorporation of lipids of high density lipoprotein) at both the apical and basolateral surfaces of polarized Sertoli cells. Finally, SR-BI expression at both the protein and mRNA levels was stimulated by FSH in cultured Sertoli cells. These results indicate that SR-BI functions on both the apical and basolateral plasma membranes of Sertoli cells, and that SR-BI expression in Sertoli cells changes during the spermatogenic cycle and is stimulated, at least in cultures, by FSH.

The predominance of one of the SR-BI isoforms is associated with increased esterified cholesterol levels not apoptosis in mink testis

“…Our observation of SR-BI localized to mink Sertoli cells agrees with the finding of the receptor protein and mRNA (39) and of SR-BI as a phagocytosis-inducing phospholipid phosphatidylserine receptor in rat Sertoli cells (37). In addition, our detection of SR-BI on testicular cell and spermatozoan surfaces and of SR-BII on the inner acrosome overlying the nucleus is consistent with the report of z70% of SR-BI on the cell surface and z80-90% of SR-BII around the Chinese hamster ovary cell nucleus (66).…”

“…The model provides a unique opportunity to highlight the relationship between apoptosis, germ cell removal, SR-BI expression, and cholesterol levels. This information is significant because injection of a part of the extracellular domain of rat SR-BI fused with human FC in the tubules was claimed to cause an increased numbers of apoptotic germ cells (37) and because phagocytosis of apoptotic germ cells by Sertoli cells was said to be mediated by SR-BI in rodents (31,(37)(38)(39).…”

Differentiation-related changes in lipid classes with long-chain and very long-chain polyenoic fatty acids in rat spermatogenic cells

“…Sertoli cells phagocytize apoptotic bodies from germ cells (hundreds of these cells normally die daily by apoptosis in the course of sper matogenesis) by recognizing, through their scavenger receptor type I (SR-I), the PS located on the surface of apoptotic fragments ( 29 ). The SR-I is expressed on both the lateral and the apical surfaces of Sertoli cells, such expression changing with the phases of the spermatogenic cycle ( 30 ). Sertoli cells could thus use the same mechanism for phagocytizing PS-exposing, germ cell-derived apoptotic bodies and residual bodies.…”

Signalling Pathway Involving GULP, MAPK and Rac1 for SR-BI-Induced Phagocytosis of Apoptotic Cells

“…Materials-The anti-rat SR-BI monoclonal antibody 3D12 and its isotype-matched control 2F2 (mouse IgG1) were generated and characterized as described previously (10). 3D12 specifically recognizes and neutralizes rat SR-BI (no cross-reactivity to mouse SR-BI), while 2F2 generated by the same immunization does not bind to SR-BI.…”