C-terminal domains within human MT sub(1) and MT sub(2) melatonin receptors are involved in internalization processes

Melatonin, a molecule implicated in a variety of diseases, including cancer, often exerts its effects through G-protein-coupled melatonin receptors, MT sub(1) and MT sub(2). In this study, we sought to understand further the domains involved in the function and desensitization patterns of these rece...

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Veröffentlicht in:Journal of pineal research 2008-09, Vol.45 (2), p.212-218
Hauptverfasser: Sethi, Shalini, Adams, Wendy, Pollock, John, Witt-Enderby, Paula A
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Sprache:eng
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Zusammenfassung:Melatonin, a molecule implicated in a variety of diseases, including cancer, often exerts its effects through G-protein-coupled melatonin receptors, MT sub(1) and MT sub(2). In this study, we sought to understand further the domains involved in the function and desensitization patterns of these receptors through site-directed mutagenesis. Two mutations were constructed in the cytoplasmic C-terminal tail of each receptor subtype: (i) a cysteine residue in the C-terminal tail was mutated to alanine, thus removing a putative palmitoylation site, and a site possibly required for normal receptor function (MT sub(1)C7.72A and MT sub(2)C7.77A) and (ii) the C-terminal tail in the MT sub(1) and MT sub(2) receptors was truncated, removing the putative phosphorylation and beta -arrestin binding sites (MT sub(1)Y7.64 and MT sub(2)Y7.64). These mutations did not alter the affinity of 2-[ super(125)I]-iodomelatonin binding to the MT sub(1) or MT sub(2) receptors. Using confocal microscopy, it was determined that the putative palmitoylation site (cysteine residue) did not play a role in receptor internalization; however, this residue was essential for receptor function, as determined by 3',5'-cyclic adenosine monophosphate (cAMP) accumulation assays. Truncation of the C-terminal tail of both receptors (MT sub(1)Y7.64 and MT sub(2)Y7.64) inhibited internalization as well as the cAMP response, suggesting the importance of the C-terminal tail in these receptor functions.
ISSN:0742-3098
1600-079X
DOI:10.1111/j.1600-079X.2008.00579.x