| Autor: |
Matsushita M; First Department of Physiology, Okayama University Medical School, 2-5-1 Shikata-cho, Okayama 700-8558, Japan., Kozak JA, Shimizu Y, McLachlin DT, Yamaguchi H, Wei FY, Tomizawa K, Matsui H, Chait BT, Cahalan MD, Nairn AC |
| Jazyk: |
angličtina |
| Zdroj: |
The Journal of biological chemistry [J Biol Chem] 2005 May 27; Vol. 280 (21), pp. 20793-803. Date of Electronic Publication: 2005 Mar 21. |
| DOI: |
10.1074/jbc.M413671200 |
| Abstrakt: |
TRPM7/ChaK1 is a unique channel/kinase that contains a TRPM channel domain with 6 transmembrane segments fused to a novel serine-threonine kinase domain at its C terminus. The goal of this study was to investigate a possible role of kinase activity and autophosphorylation in regulation of channel activity of TRPM7/ChaK1. Residues essential for kinase activity were identified by site-directed mutagenesis. Two major sites of autophosphorylation were identified in vitro by mass spectrometry at Ser(1511) and Ser(1567), and these sites were found to be phosphorylated in intact cells. TRPM7/ChaK1 is a cation-selective channel that exhibits strong outward rectification and inhibition by millimolar levels of internal [Mg(2+)]. Mutation of the two autophosphorylation sites or of a key catalytic site that abolished kinase activity did not alter channel activity measured by whole-cell recording or Ca(2+) influx. Inhibition by internal Mg(2+) was also unaffected in the autophosphorylation site or "kinase-dead" mutants. Moreover, kinase activity was enhanced by Mg(2+), was decreased by Zn(2+), and was unaffected by Ca(2+). In contrast, channel activity was inhibited by all three of these divalent cations. However, deletion of much of C-terminal kinase domain resulted in expression of an apparently inactive channel. We conclude that neither current activity nor regulation by internal Mg(2+) is affected by kinase activity or autophosphorylation but that the kinase domain may play a structural role in channel assembly or subcellular localization. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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