Roles of endogenously synthesized sterols in the endocytic pathway.
The effect(s) of endogenously synthesized cholesterol (endo-CHOL) on the endosomal system in mammalian cells has not been examined. Here we treated Chinese hamster ovary cell lines with lovastatin (a hydroxymethylglutaryl-CoA reductase inhibitor) and mevalonate (a precursor for isoprenoids) to block endo-CHOL synthesis and then examined its effects on the fate of cholesterol liberated from low density lipoprotein (LDL-CHOL). The results showed that blocking endo-CHOL synthesis for 2 h or longer does not impair the hydrolysis of cholesteryl esters but partially impairs the transport of LDL-CHOL to the plasma membrane. Blocking endo-CHOL synthesis for 2 h or longer also alters the localization patterns of the late endosomes/lysosomes and retards their motility, as monitored by time-lapse microscopy. LDL-CHOL overcomes the effect of blocking endo-CHOL synthesis on endosomal localization patterns and on endosomal motility. Overexpressing Rab9, a key late endosomal small GTPase, relieves the endosomal cholesterol accumulation in Niemann-Pick type C1 cells but does not revert the reduced endosomal motility caused by blocking endo-CHOL synthesis. Our results suggested that endo-CHOL contributes to the cholesterol content of late endosomes and controls its motility, in a manner independent of NPC1. These results also supported the concept that endosomal motility plays an important role in controlling cholesterol trafficking activities.
Sugii
Shigeki
S
Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
Lin
Song
S
Ohgami
Nobutaka
N
Ohashi
Masato
M
Chang
Catherine C Y
CC
Chang
Ta-Yuan
TY
D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000378:metabolism; D002784:Cholesterol / Q000378:metabolism; D002788:Cholesterol Esters / Q000737:chemistry; D006224:Cricetinae; D004705:Endocytosis; D011992:Endosomes; D006868:Hydrolysis; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors / Q000494:pharmacology; D008148:Lovastatin / Q000494:pharmacology; D008954:Models, Biological; D013261:Sterols / Q000378:metabolism*; D013997:Time Factors
D002788:Cholesterol Esters; D019161:Hydroxymethylglutaryl-CoA Reductase Inhibitors; D013261:Sterols; C021976:cholesteryl linoleate; D002784:Cholesterol; D008148:Lovastatin