Apomine, a novel hypocholesterolemic agent, accelerates degradation of 3-hydroxy-3-methylglutaryl-coenzyme A reductase and stimulates low density lipoprotein receptor activity.
Apomine, a novel 1,1-bisphosphonate ester, has been shown to lower plasma cholesterol concentration in several species. Here we show that Apomine reduced the levels of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR), the rate-limiting enzyme in the mevalonate pathway, both in rat liver and in cultured cells. Apomine resembles sterols such as 25-hydroxycholesterol in its ability to potently accelerate the rate of HMGR degradation by the ubiquitin-proteasome pathway, a process that depends on the transmembrane domain of the enzyme. The similarity between Apomine and sterols in promoting rapid HMGR degradation extends to its acute requirements for ongoing protein synthesis and mevalonate-derived non-sterol product(s) as a co-regulator. Yet, at suboptimal concentrations, sterols potentiated the effect of Apomine in stimulating HMGR degradation, indicating that these agents act via distinct modes. Furthermore, unlike sterols, Apomine inhibited the activity of acyl-CoA:cholesterol acyltransferase in intact cells but not in cell-free extracts. Apomine stimulated the cleavage of the precursor of sterol-regulatory element-binding protein-2 and increased the activity of low density lipoprotein receptor pathway. This Apomine-enhanced activation of sterol-regulatory element-binding protein-2 was prevented by sterols or mevalonate. Taken together, our results provide a molecular mechanism for the hypocholesterolemic activity of Apomine.
Roitelman
Joseph
J
Institute of Lipid and Atherosclerosis Research, Sheba Medical Center, Tel Hashomer 52621, Israel.
Masson
Danièle
D
Avner
Rachel
R
Ammon-Zufferey
Corinne
C
Perez
Anne
A
Guyon-Gellin
Yves
Y
Bentzen
Craig L
CL
Niesor
Eric J
EJ
D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology*; D016466:CHO Cells; D002474:Cell-Free System; D002478:Cells, Cultured; D002784:Cholesterol / Q000737:chemistry; D006224:Cricetinae; D004268:DNA-Binding Proteins / Q000378:metabolism; D004164:Diphosphonates / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D006367:HeLa Cells; D006801:Humans; D006888:Hydroxycholesterols / Q000737:chemistry; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism*; D015151:Immunoblotting; D008099:Liver / Q000201:enzymology; D008297:Male; D008956:Models, Chemical; D011233:Precipitin Tests; D051381:Rats; D017208:Rats, Wistar; D011973:Receptors, LDL / Q000378:metabolism*; D051782:Sterol Regulatory Element Binding Protein 2; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism
D000924:Anticholesteremic Agents; D004268:DNA-Binding Proteins; D004164:Diphosphonates; D006888:Hydroxycholesterols; D011973:Receptors, LDL; C497390:SREBF2 protein, human; D051782:Sterol Regulatory Element Binding Protein 2; D014157:Transcription Factors; C407151:apomine; C007997:25-hydroxycholesterol; D002784:Cholesterol; D006903:Hydroxymethylglutaryl CoA Reductases