title: Inhibitor of myogenic family, a novel suppressor of store-operated currents through an interaction with TRPC1.
abstract: Depletion of intracellular Ca2+ stores leads to the activation of Ca2+ inflow through store-operated Ca2+ channels. Although the identity of these channels is unknown, there is considerable evidence that the transient receptor potential channel 1 (TRPC1) participates in the formation of these channels. We show that TRPC1 physically interacts with the a-isoform of the inhibitor of the myogenic family (I-mfa), a known inhibitor of basic helix-loop-helix transcription factors, in vitro and in vivo. The interaction is mediated by the C-terminal cytoplasmic tail of TRPC1 and the C-terminal cysteine-rich domain of I-mfa. Using the whole cell configuration of the patch clamp technique, we show that ectopic expression of I-mfa in CHO-K1 cells reduces native store-activated Ca2+ currents, whereas knock-down of endogenous I-mfa in A431 cells by RNA interference enhances these currents. Pipette perfusion of purified recombinant I-mfa rescues the effect of I-mfa knock-down on store-operated conductance. Finally, cell dialysis with a monoclonal antibody specific to TRPC1 results in the suppression of store-activated conductance in cells lacking I-mfa, but not in I-mfa expressing cells. We propose that I-mfa functions as a molecular switch to suppress the store dependence of TRPC1.
authors.affiliation: Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.
authors.forename: Rong
authors.initials: R
authors.lastname: Ma
authors.forename: Dana
authors.initials: D
authors.lastname: Rundle
authors.forename: Jeanie
authors.initials: J
authors.lastname: Jacks
authors.forename: Marci
authors.initials: M
authors.lastname: Koch
authors.forename: Tamyra
authors.initials: T
authors.lastname: Downs
authors.forename: Leonidas
authors.initials: L
authors.lastname: Tsiokas
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism*; D002460:Cell Line; D006224:Cricetinae; D003545:Cysteine / Q000737:chemistry; D003593:Cytoplasm / Q000378:metabolism; D004594:Electrophysiology; D005260:Female; D006801:Humans; D007668:Kidney / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D018006:Myogenic Regulatory Factors / Q000235:genetics* / Q000502:physiology*; D018008:Myogenin / Q000378:metabolism; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D020033:Protein Isoforms; D017434:Protein Structure, Tertiary; D034622:RNA Interference; D051381:Rats; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D050052:TRPC Cation Channels; D014157:Transcription Factors / Q000737:chemistry; D014162:Transfection; D020798:Two-Hybrid System Techniques
chemical_list: D000911:Antibodies, Monoclonal; D015220:Calcium Channels; C503799:MYOG protein, human; C491077:Mdfi protein, mouse; C503801:Myog protein, mouse; C503803:Myog protein, rat; D018006:Myogenic Regulatory Factors; D018008:Myogenin; D020033:Protein Isoforms; D011994:Recombinant Proteins; D050052:TRPC Cation Channels; D014157:Transcription Factors; C096351:transient receptor potential cation channel, subfamily C, member 1; C101295:MDFI protein, human; D003545:Cysteine; D002118:Calcium