The selective pathway and a high-density lipoprotein receptor (SR-BI) in ovarian granulosa cells of the mouse.
We recently reported that rat luteinized ovary tissue and primary cultures of rat ovarian granulosa cells reveal a remarkably tight functional correlation between expressed selective uptake of lipoprotein cholesteryl esters and the expression of an HDL receptor protein, scavenger receptor, class B, type I (SR-BI). In the current study, we examine these same processes in C57 mouse granulosa cells and report a different correlation. Unlike the rat cells, non-hormone stimulated mouse granulosa cells are able to effectively carry out their selective pathway functions and secrete HDL-derived progestins despite low levels of SR-BI and barely detectable levels of SR-BII (an isoform of SR-BI). Once stimulated with trophic hormones or Bt2cAMP, small (30-40%) increases are observed in selective pathway functions, but major (approximately 20-fold) increases are seen in SR-BI and SR-BII expression: thus, relatively little is gained in selective cholesteryl ester uptake by mouse granulosa cells even though SR-BI and SR-BII levels are greatly increased. The importance of the HDL receptor proteins to the selective pathway remains clear, however, since a significant portion of the selective process in both basal and stimulated granulosa cells is inhibitable by the use of blocking antibody. Another surface protein, caveolin, previously reported to co-localize with SR-BI in mouse cells shows no change in expression during periods when SR-BI/BII levels are undergoing major shifts.
Reaven
E
E
Education and Clinical Center, VA Palo Alto Health Care System, CA 94304, USA.
Lua
Y
Y
Nomoto
A
A
Temel
R
R
Williams
D L
DL
van der Westhuyzen
D R
DR
Azhar
S
S
D000595:Amino Acid Sequence; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D018955:CD36 Antigens / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins; D051242:Caveolin 1; D022461:Caveolins; D002788:Cholesterol Esters / Q000378:metabolism; D005260:Female; D006107:Granulosa Cells / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D008075:Lipoproteins, HDL / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D011374:Progesterone / Q000096:biosynthesis; D016601:RNA-Binding Proteins; D051381:Rats; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein / Q000235:genetics / Q000378:metabolism*; D051116:Receptors, Scavenger; D051122:Scavenger Receptors, Class B; D013045:Species Specificity; D014018:Tissue Distribution