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Environmental Circadian Modulators Target Melatonin Receptors in Pancreatic β‐Cells
Author(s) -
Jones Anthony,
PopovskaGorevski Marina,
Mastandrea Lucy,
Rajnarayanan Rajendram,
Dubocovich Margarita
Publication year - 2015
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.29.1_supplement.776.3
Subject(s) - melatonin , circadian rhythm , receptor , melatonin receptor , endocrinology , chemistry , medicine , microbiology and biotechnology , biology
In silico 3D modelling and 2‐[ 125 I]‐iodomelatonin binding to human MT 1 and MT 2 melatonin receptors identified the carbamate insecticides, carbaryl and carbofuran, as potential melatonin receptor circadian modulators (M P‐G et al., EB Abstract, 2014). In humans, signaling through MT 1 and MT 2 melatonin receptors modulates insulin secretion from pancreatic β‐cells (Int J Mol Sci 14: 6981, 2013). This study determined the pharmacological profile of melatonin receptors and the effect of carbamate insecticides in rat insulinoma cells (INS‐1), a model for pancreatic β‐cells. Saturation binding with 2‐[ 125 I]‐Iodomelatonin (1 to 1000 pM) to INS‐1 cell membranes yielded a K D of 50.2 ± 13.2 pM and a B max of 10.8 ± 2.8 fmol/mg protein (n=5). Competition binding of melatonin and the competitive melatonin receptor antagonist luzindole for 2‐[ 125 I]‐iodomelatonin binding to INS‐1 cell membranes yielded K i of 83 ± 18 pM (n=9) and 0.50 ± 0.14 µM (n=4), respectively. The affinity of luzindole and the reported low to undetectable levels of MT 2 receptor expression in INS‐1 cells, suggest that 2‐[ 125 I]‐iodomelatonin binds primarily to MT 1 receptors. The K i for carbaryl was 2.59 ± 0.54 µM (n=7) while concentrations as high as 1 mM of carbofuran did not compete for 2‐[ 125 I]‐iodomelatonin binding to INS‐1 cell membranes. The presence of GTP (100 µM) did not alter the competition of carbaryl for 2‐[ 125 I]‐iodomelatonin binding (Ki = 5.39 ± 0.19 µM, n=4). These results suggest that carbaryl may potentially block melatonin receptors in INS‐1 cells. Supported by ES 023684 to MLD and RVR.