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.
Labit-Le Bouteiller
C
C
Sanofi Recherche, Centre de Labège, France.
Jamme
M F
MF
David
M
M
Silve
S
S
Lanau
C
C
Dhers
C
C
Picard
C
C
Rahier
A
A
Taton
M
M
Loison
G
G
Caput
D
D
Ferrara
P
P
Lupker
J
J
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