出版社：American Society for Biochemistry and Molecular Biology
摘要：Rat ovarian granulosa rely heavily on lipoprotein-derived cholesterolfor steroidogenesis, which is principally supplied by the LDLreceptor- and scavenger receptor class B type I (SR-BI)-mediatedpathways. In this study, we characterized the hormonal and cholesterolregulation of another member of the LDL receptor superfamily,low density lipoprotein receptor-related protein (LRP), andits role in granulosa cell steroidogenesis. Coincubation ofcultured granulosa cells with LDL and N6,O2'-dibutyryl adenosine3',5'-cyclic monophosphate (Bt2cAMP) greatly increased the mRNA/proteinlevels of LRP. Bt2cAMP and Bt2cAMP plus human (h)LDL also enhancedSR-BI mRNA levels. However, there was no change in the expressionof receptor-associated protein, a chaperone for LRP, or anotherlipoprotein receptor, LRP8/apoER2, in response to Bt2cAMP plushLDL, whereas the mRNA expression of LDL receptor was reducedsignificantly. The induced LRP was fully functional, mediatingincreased uptake of its ligand, 2-macroglobulin. The level ofbinding of another LRP ligand, chylomicron remnants, did notincrease, although the extent of remnant degradation that couldbe attributed to the LRP doubled in cells with increased levelsof LRP. The addition of lipoprotein-type LRP ligands such aschylomicron remnants and VLDL to the incubation medium significantlyincreased the progestin production under both basal and stimulatedconditions. In summary, our studies demonstrate a role for LRPin lipoprotein-supported ovarian granulosa cell steroidogenesis.Supplementary key words low density lipoprotein • adenosine 3',5'-cyclic monophosphate • low density lipoprotein receptor-related protein
Abbreviations: apoE, apolipoprotein E; Bt2cAMP, N6,O2'-dibutyryl adenosine 3',5'-cyclic monophosphate; CE, cholesteryl ester; DRB, 5,6-dichloro-1-ß-D-ribofuranosylbenzimidazole; GST, glutathione S-transferase; LRP, low density lipoprotein receptor-related protein; RAP, receptor-associated protein; RPA, RNase protection assay; SR-BI, scavenger receptor class B type I
2-macroglobulin. The level of binding of another LRP ligand, chylomicron remnants, did not increase, although the extent of remnant degradation that could be attributed to the LRP doubled in cells with increased levels of LRP. The addition of lipoprotein-type LRP ligands such as chylomicron remnants and VLDL to the incubation medium significantly increased the progestin production under both basal and stimulated conditions. In summary, our studies demonstrate a role for LRP in lipoprotein-supported ovarian granulosa cell steroidogenesis.
Supplementary key words low density lipoprotein • adenosine 3',5'-cyclic monophosphate • low density lipoprotein receptor-related protein
Abbreviations: apoE, apolipoprotein E; Bt2cAMP, N6,O2'-dibutyryl adenosine 3',5'-cyclic monophosphate; CE, cholesteryl ester; DRB, 5,6-dichloro-1-ß-D-ribofuranosylbenzimidazole; GST, glutathione S-transferase; LRP, low density lipoprotein receptor-related protein; RAP, receptor-associated protein; RPA, RNase protection assay; SR-BI, scavenger receptor class B type I
