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Pflugers Arch. 2015 Aug;467(8):1723-1732. doi: 10.1007/s00424-014-1610-3. Epub 2014 Sep 18.

Casein kinase-mediated phosphorylation of serine 839 is necessary for basolateral localization of the Ca²⁺-activated non-selective cation channel TRPM4.

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Programa de Biología Celular y Molecular, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile.
Centro de Estudios Moleculares de la Célula (CEMC), Facultad de Medicina, Universidad de Chile, Santiago, Chile.
Department of Neurobiology, Physiology and Behavior, College of Biological Sciences, University of California, Davis CA 95616, USA.
Department of Physiology, Kyung Hee University School of Medicine, Seoul, South Korea 130-701.
Programa de Fisiopatología, Facultad de Medicina, ICBM, Universidad de Chile, Santiago, Chile.
Department of Physiology and Membrane Biology, School of Medicine, University of California, Davis CA 95616, USA.
Contributed equally


Transient receptor potential melastatin-like 4 (TRPM4) is a Ca(2+)-activated non-selective cation channel expressed in a wide range of human tissues. TRPM4 participates in a variety of physiological processes such as T cell activation, myogenic vasoconstriction, and allergic reactions. TRPM4 Ca(2+) sensitivity is enhanced by calmodulin (CaM) and phosphathydilinositol 4, 5-bisphosphate (PI(4,5)P2) binding, as well as, under certain conditions, PKC activation. However, information as to the mechanisms of modulation of this channel remains unknown, including direct identification of phosphorylation sites on TRPM4 and their role in channel features. Here, we use mass-spectrometric-based proteomic approaches (immunoprecipitation and tandem mass spectrometry) to unambiguously identify S839 as a phosphorylation site present on human TRPM4 expressed in a human cell line. Site-directed mutagenesis employing a serine to alanine mutation to eliminate phosphorylation, and a phospho-mimetic aspartate mutation, as well as biochemical and immunocytochemical experiments, revealed a role for S839 phosphorylation in the basolateral expression of TRPM4 channels in epithelial cells. Moreover, we demonstrated that casein kinase 1 (CK1) phosphorylates S839 and is responsible for the basolateral localization of TRPM4.

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