Structural landscape of activation, desensitization and inhibition in the human TRPM4 channel

Abstract

TRPM4 is a member of the transient receptor potential melastatin channel subfamily and functions as a Ca²⁺-activated monovalent-selective cation channel. It is widely expressed in various cells and tissues, where its activation depolarizes the plasma membrane potential and modulates various Ca²⁺-dependent biological processes. TRPM4 activity is potentiated by membrane phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P₂) and inhibited by cytosolic free adenosine triphosphate (ATP), allowing the channel to transition between different functional states in response to dynamic changes in cellular Ca²⁺, ATP and PtdIns(4,5)P₂ levels during signaling events. Here we present single-particle cryo-electron microscopy structures of human TRPM4 in four distinct states: apo closed, Ca²⁺-bound putative desensitized, Ca²⁺-PtdIns(4,5)P₂-bound open and ATP-bound inhibited. Combined with mutagenesis and electrophysiological analyses, these structures reveal the molecular mechanisms underlying TRPM4 activation, desensitization and inhibition. Given the central roles of Ca²⁺, PtdIns(4,5)P₂ and ATP in cellular signaling, this work provides a structural foundation to decipher the physiological functions of TRPM4 across diverse biological systems.