title: Ultradian rhythm in the intestine of Caenorhabditis elegans is controlled by the C-terminal region of the FLR-1 ion channel and the hydrophobic domain of the FLR-4 protein kinase.
abstract: Defecation behavior in Caenorhabditis elegans is driven by an endogenous ultradian clock in the intestine. Its periods are positively regulated by FLR-1, an ion channel of the epithelial sodium channel/degenerin superfamily, and FLR-4, a protein kinase with a hydrophobic domain at the carboxyl terminus. FLR-1 has many putative phosphorylation sites in the C-terminal intracellular region. This structure implies that the periods may be regulated by the phosphorylation of FLR-1 by FLR-4, but it remains to be clarified. Here, we show that a truncated FLR-1 lacking the C-terminal intracellular region resulted in longer periods, suggesting that this region is involved in the negative regulation of defecation cycle periods. Contrary to our expectation, FLR-4 was still necessary for the function of the truncated FLR-1. Furthermore, FLR-4 containing a kinase-dead mutation or lacking the whole kinase domain was sufficient for normal defecation cycle periods. FLR-4 was necessary for the stable expression of FLR-1::GFP, and its hydrophobic domain was sufficient also for this function. FLR-1 and FLR-4 are often colocalized in the plasma membrane. These data showed an unexpected role of FLR-4: its hydrophobic domain stabilizes the FLR-1 ion channel, a key regulator of defecation cycle periods in the intestine.
authors.affiliation: Structural Biology Center, National Institute of Genetics, Mishima, Shizuoka-ken, Japan.
authors.forename: Yuri
authors.initials: Y
authors.lastname: Kobayashi
authors.forename: Koutarou D
authors.initials: KD
authors.lastname: Kimura
authors.forename: Isao
authors.initials: I
authors.lastname: Katsura
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001665:Binding Sites; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D002940:Circadian Rhythm; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007413:Intestinal Mucosa / Q000378:metabolism*; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009154:Mutation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D015222:Sodium Channels / Q000235:genetics / Q000378:metabolism*
chemical_list: D029742:Caenorhabditis elegans Proteins; C561471:FLR-1 protein, C elegans; D015222:Sodium Channels; D049452:Green Fluorescent Proteins; D011494:Protein Kinases; C502826:FLR-4 protein, C elegans; D017346:Protein Serine-Threonine Kinases