On potential interactions between non-selective cation channel TRPM4 and sulfonylurea receptor SUR1

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Abstract

The sulfonylurea receptor SUR1 associates with Kir6.2 or Kir6.1 to form K ATP channels, which link metabolism to excitability in multiple cell types. The strong physical coupling of SUR1 with Kir6 subunits appears exclusive, but recent studies argue that SUR1 also modulates TRPM4, a member of the transient receptor potential family of non-selective cation channels. It has been reported that, following stroke, brain, or spinal cord injury, SUR1 is increased in neurovascular cells at the site of injury. This is accompanied by up-regulation of a non-selective cation conductance with TRPM4-like properties and apparently sensitive to sulfonylureas, leading to the postulation that posttraumatic non-selective cation currents are determined by TRPM4/SUR1channels.Toinvestigate the mechanistic hypothesis for the coupling between TRPM4 and SUR1, we performed electrophysiological and FRET studies in COSm6 cells expressing TRPM4 channels with or without SUR1. TRPM4-mediated currents were Ca 2+-activated, voltage-dependent, underwent desensitization, and were inhibited by ATP but were insensitive to glibenclamide and tolbutamide. These properties were not affected by cotransfection with SUR1. When the same SUR1 was cotransfected with Kir6.2, functional K ATP channels were formed. In cells cotransfected with Kir6.2, SUR1, and TRPM4, we measured K ATP-mediated K + currents and Ca 2+-activated, sulfonylurea-insensitive Na + currents in the same patch, further showing that SUR1 controls K ATP channel activity but not TRPM4 channels. FRET signal between fluorophore-tagged TRPM4 subunits was similar to that between Kir6.2 and SUR1, whereas there was no detectable FRET efficiency between TRPM4 and SUR1. Our data suggest that functional or structural association of TRPM4 and SUR1 is unlikely.

Original languageEnglish
Pages (from-to)8746-8756
Number of pages11
JournalJournal of Biological Chemistry
Volume287
Issue number12
DOIs
StatePublished - Mar 16 2012

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