Inhibition of RPE65 Retinol Isomerase Activity by Inhibitors of Lipid Metabolism
| Autor: | Eugenia Poliakov, Susan Gentleman, T. Michael Redmond, Abdulkerim Eroglu |
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| Rok vydání: | 2016 |
| Předmět: |
cis-trans-Isomerases
0301 basic medicine Isomerase activity Stereochemistry Molecular Sequence Data Isomerase Biology Biochemistry 03 medical and health sciences chemistry.chemical_compound Coenzyme A Ligases Animals Humans Moiety Amino Acid Sequence Enzyme Inhibitors Molecular Biology chemistry.chemical_classification Binding Sites 030102 biochemistry & molecular biology Cell Biology eye diseases Retinol isomerase activity Triacsin C HEK293 Cells 030104 developmental biology Enzyme chemistry Enzyme inhibitor Cis-trans-Isomerases Enzymology biology.protein sense organs Triazenes Chickens Protein Binding |
| Zdroj: | Journal of Biological Chemistry. 291:4966-4973 |
| ISSN: | 0021-9258 |
| Popis: | RPE65 is the isomerase catalyzing conversion of all-trans-retinyl ester (atRE) into 11-cis-retinol in the retinal visual cycle. Crystal structures of RPE65 and site-directed mutagenesis reveal aspects of its catalytic mechanism, especially retinyl moiety isomerization, but other aspects remain to be determined. To investigate potential interactions between RPE65 and lipid metabolism enzymes, HEK293-F cells were transfected with expression vectors for visual cycle proteins and co-transfected with either fatty acyl:CoA ligases (ACSLs) 1, 3, or 6 or the SLC27A family fatty acyl-CoA synthase FATP2/SLCA27A2 to test their effect on isomerase activity. These experiments showed that RPE65 activity was reduced by co-expression of ACSLs or FATP2. Surprisingly, however, in attempting to relieve the ACSL-mediated inhibition, we discovered that triacsin C, an inhibitor of ACSLs, also potently inhibited RPE65 isomerase activity in cellulo. We found triacsin C to be a competitive inhibitor of RPE65 (IC50 = 500 nm). We confirmed that triacsin C competes directly with atRE by incubating membranes prepared from chicken RPE65-transfected cells with liposomes containing 0-1 μM atRE. Other inhibitors of ACSLs had modest inhibitory effects compared with triascin C. In conclusion, we have identified an inhibitor of ACSLs as a potent inhibitor of RPE65 that competes with the atRE substrate of RPE65 for binding. Triacsin C, with an alkenyl chain resembling but not identical to either acyl or retinyl chains, may compete with binding of the acyl moiety of atRE via the alkenyl moiety. Its inhibitory effect, however, may reside in its nitrosohydrazone/triazene moiety. |
| Databáze: | OpenAIRE |
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