The transient receptor potential, TRP4, cation channel is a novel member of the family of calmodulin binding proteins.
The mammalian gene products, transient receptor potential (trp)1 to trp7, are related to the Drosophila TRP and TRP-like ion channels, and are candidate proteins underlying agonist-activated Ca(2+)-permeable ion channels. Recently, the TRP4 protein has been shown to be part of native store-operated Ca(2+)-permeable channels. These channels, most likely, are composed of other proteins in addition to TRP4. In the present paper we report the direct interaction of TRP4 and calmodulin (CaM) by: (1) retention of in vitro translated TRP4 and of TRP4 protein solubilized from bovine adrenal cortex by CaM-Sepharose in the presence of Ca(2+), and (2) TRP4-glutathione S-transferase pull-down experiments. Two domains of TRP4, amino acid residues 688-759 and 786-848, were identified as being able to interact with CaM. The binding of CaM to both domains occurred only in the presence of Ca(2+) concentrations above 10 microM, with half maximal binding occurring at 16.6 microM (domain 1) and 27.9 microM Ca(2+) (domain 2). Synthetic peptides, encompassing the two putative CaM binding sites within these domains and covering amino acid residues 694-728 and 829-853, interacted directly with dansyl-CaM with apparent K(d) values of 94-189 nM. These results indicate that TRP4/Ca(2+)-CaM are parts of a signalling complex involved in agonist-induced Ca(2+) entry.
Trost
C
C
Institut für Pharmakologie und Toxikologie der Universität des Saarlandes, D-66421 Homburg, Germany. claudia.trost@med-rz.uni-sb.de
Bergs
C
C
Himmerkus
N
N
Flockerzi
V
V
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000737:chemistry / Q000378:metabolism*; D002147:Calmodulin / Q000378:metabolism*; D002148:Calmodulin-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D002417:Cattle; D051379:Mice; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000138:chemical synthesis / Q000737:chemistry / Q000378:metabolism; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D050052:TRPC Cation Channels
D015220:Calcium Channels; D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; D010446:Peptide Fragments; D050052:TRPC Cation Channels; C489571:TRPC4 ion channel; C096351:transient receptor potential cation channel, subfamily C, member 1; D002118:Calcium