Transient Receptor Potential Melastatin 1 (TRPM1) Is an Ion-conducting Plasma Membrane Channel Inhibited by Zinc Ions

TRPM1 is the founding member of the melastatin subgroup of transient receptor potential (TRP) proteins, but it has not yet been firmly established that TRPM1 proteins form ion channels. Consequently, the biophysical and pharmacological properties of these proteins are largely unknown. Here we show t...

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Published in:	The Journal of biological chemistry Vol. 286; no. 14; pp. 12221 - 12233
Main Authors:	Lambert, Sachar, Drews, Anna, Rizun, Oleksandr, Wagner, Thomas F.J., Lis, Annette, Mannebach, Stefanie, Plant, Sandra, Portz, Melanie, Meissner, Marcel, Philipp, Stephan E., Oberwinkler, Johannes
Format:	Journal Article
Language:	English
Published:	United States Elsevier Inc 08-04-2011 American Society for Biochemistry and Molecular Biology
Subjects:	Cell Line Cell Membrane - metabolism Electrophysiology Fluorescence Resonance Energy Transfer Humans Immunoprecipitation Ion Channel Pharmacology Ion Channel Selectivity Ion Channels Molecular Biophysics Mutation Pancreatic Islet Retina Retinal Bipolar Cell TRP Channels TRPM Cation Channels - drug effects TRPM Cation Channels - genetics TRPM Cation Channels - metabolism Zinc Zinc - pharmacology Pancreatic Islet Ion Channel Pharmacology Ion Channels TRP Channels Retina Retinal Bipolar Cell Ion Channel Selectivity Zinc
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Summary:	TRPM1 is the founding member of the melastatin subgroup of transient receptor potential (TRP) proteins, but it has not yet been firmly established that TRPM1 proteins form ion channels. Consequently, the biophysical and pharmacological properties of these proteins are largely unknown. Here we show that heterologous expression of TRPM1 proteins induces ionic conductances that can be activated by extracellular steroid application. However the current amplitudes observed were too small to enable a reliable biophysical characterization. We overcame this limitation by modifying TRPM1 channels in several independent ways that increased the similarity to the closely related TRPM3 channels. The resulting constructs produced considerably larger currents after overexpression. We also demonstrate that unmodified TRPM1 and TRPM3 proteins form functional heteromultimeric channels. With these approaches, we measured the divalent permeability profile and found that channels containing the pore of TRPM1 are inhibited by extracellular zinc ions at physiological concentrations, in contrast to channels containing only the pore of TRPM3. Applying these findings to pancreatic β cells, we found that TRPM1 proteins do not play a major role in steroid-activated currents of these cells. The inhibition of TRPM1 by zinc ions is primarily due to a short stretch of seven amino acids present only in the pore region of TRPM1 but not of TRPM3. Combined, our data demonstrate that TRPM1 proteins are bona fide ion-conducting plasma membrane channels. Their distinct biophysical properties allow a reliable identification of endogenous TRPM1-mediated currents.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 Present address: Dept. of Cell Biology and Dorris Neuroscience Center, The Scripps Research Institute, La Jolla, CA 92037. Present address: Center for Biomedical Research at The Queen's Medical Center and John A. Burns School of Medicine at the University of Hawaii, Honolulu, HI 96813. Both authors contributed equally to this work.
ISSN:	0021-9258 1083-351X
DOI:	10.1074/jbc.M110.202945