Antiproliferative effects of SR31747A in animal cell lines are mediated by inhibition of cholesterol biosynthesis at the sterol isomerase step.
SR31747A is a new sigma ligand exhibiting immunosuppressive properties and antiproliferative activity on lymphocyte cells. Only two subtypes of sigma receptor, namely the sigma1 receptor and emopamil-binding protein, have been characterised molecularly. Only the sigma1 receptor has been shown to bind (Z)N-cyclohexyl-N-ethyl-3-(3-chloro4-cyclohexylphenyl)pro pen-2-ylamine hydrochloride (SR31747A) with high affinity. It was demonstrated that the SR31747A effect on the inhibition of T-cell proliferation was consistent with a sigma1 receptor-mediated event. In this report, binding experiments and sterol isomerase assays, using recombinant yeast strains, indicate that the recently cloned emopamil-binding protein is a new SR31747A-binding protein whose activity is inhibited by SR31747A. Sterol analyses reveal the accumulation of a delta8-cholesterol isomer at the expense of cholesterol in SR31747A-treated cells, suggesting that cholesterol biosynthesis is inhibited by SR31747A at the delta8-delta7 sterol isomerase step in animal cells. This observation is consistent with a sterol isomerase role of the emopamil-binding protein in the cholesterol biosynthetic pathway in animal cells. In contrast, there is no evidence for such a role of the sigma1 receptor, in spite of the structural similarity shared by this protein and yeast sterol isomerase. We have found that SR31747A also exerts anti-proliferative effects at nanomolar concentrations on various established cell lines. The antiproliferative activity of SR31747A is reversed by cholesterol. Sterol-isomerase overproduction enhances resistance of CHO cells. This last observation strongly suggests that sterol isomerase is implicated in the antiproliferative effect of the drug in established cell lines.
Sanofi Recherche, Centre de Labège, France.
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Labit-Le Bouteiller
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Jamme
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David
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Silve
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Lanau
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Dhers
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Picard
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Rahier
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Taton
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Loison
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Caput
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Ferrara
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Lupker
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects*; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D003510:Cyclohexanes / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005656:Fungal Proteins / Q000378:metabolism; D006801:Humans; D051379:Mice; D011485:Protein Binding; D011957:Receptors, Opioid; D017480:Receptors, sigma / Q000378:metabolism*; D013251:Steroid Isomerases / Q000037:antagonists & inhibitors*; D000097605:Sigma-1 Receptor
D002352:Carrier Proteins; D002784:Cholesterol; D003510:Cyclohexanes; D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D011957:Receptors, Opioid; D017480:Receptors, sigma; D013251:Steroid Isomerases; D000097605:Sigma-1 Receptor; C088447:SR 31747; C490380:Ebp protein, mouse; C090445:EBP protein, human