title: Alternative splicing of a protein domain indispensable for function of transient receptor potential melastatin 3 (TRPM3) ion channels.
abstract: TRPM3 channels form ionotropic steroid receptors in the plasma membrane of pancreatic β and dorsal root ganglion cells and link steroid hormone signaling to insulin release and pain perception, respectively. We identified and compared the function of a number of TRPM3 splice variants present in mouse, rat and human tissues. We found that variants lacking a region of 18 amino acid residues display neither Ca(2+) entry nor ionic currents when expressed alone. Hence, splicing removes a region that is indispensable for channel function, which is called the ICF region. TRPM3 variants devoid of this region (TRPM3ΔICF), are ubiquitously present in different tissues and cell types where their transcripts constitute up to 15% of the TRPM3 isoforms. The ICF region is conserved throughout the TRPM family, and its presence in TRPM8 proteins is also necessary for function. Within the ICF region, 10 amino acid residues form a domain essential for the formation of operative TRPM3 channels. TRPM3ΔICF variants showed reduced interaction with other TRPM3 isoforms, and their occurrence at the cell membrane was diminished. Correspondingly, coexpression of ΔICF proteins with functional TRPM3 subunits not only reduced the number of channels but also impaired TRPM3-mediated Ca(2+) entry. We conclude that TRPM3ΔICF variants are regulatory channel subunits fine-tuning TRPM3 channel activity.
authors.affiliation: From the Experimentelle und Klinische Pharmakologie und Toxikologie, Universität des Saarlandes, 66421 Homburg, Germany.
authors.forename: Julia
authors.initials: J
authors.lastname: Frühwald
authors.forename: Julia
authors.initials: J
authors.lastname: Camacho Londoño
authors.forename: Sandeep
authors.initials: S
authors.lastname: Dembla
authors.forename: Stefanie
authors.initials: S
authors.lastname: Mannebach
authors.forename: Annette
authors.initials: A
authors.lastname: Lis
authors.forename: Anna
authors.initials: A
authors.lastname: Drews
authors.forename: Ulrich
authors.initials: U
authors.lastname: Wissenbach
authors.forename: Johannes
authors.initials: J
authors.lastname: Oberwinkler
authors.forename: Stephan E
authors.initials: SE
authors.lastname: Philipp
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D020013:Calcium Signaling; D017124:Conserved Sequence; D005091:Exons; D057809:HEK293 Cells; D006801:Humans; D047468:Immunoprecipitation; D008564:Membrane Potentials; D051379:Mice; D008969:Molecular Sequence Data; D018408:Patch-Clamp Techniques; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D025941:Protein Interaction Mapping; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D022821:RNA Splice Sites; D051381:Rats; D017386:Sequence Homology, Amino Acid; D050053:TRPM Cation Channels / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D020033:Protein Isoforms; D022821:RNA Splice Sites; D050053:TRPM Cation Channels; C475667:TRPM3 protein, human