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

Genes Cells. 2011 May;16(5):565-75. doi: 10.1111/j.1365-2443.2011.01508.x.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Animals, Genetically Modified
  • Binding Sites
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans / metabolism*
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism*
  • Cell Membrane / metabolism
  • Circadian Rhythm
  • Green Fluorescent Proteins / genetics
  • Green Fluorescent Proteins / metabolism
  • Intestinal Mucosa / metabolism*
  • Microscopy, Confocal
  • Microscopy, Fluorescence
  • Mutation
  • Protein Kinases / genetics
  • Protein Kinases / metabolism
  • Protein-Serine-Threonine Kinases / genetics
  • Protein-Serine-Threonine Kinases / metabolism*
  • Sodium Channels / genetics
  • Sodium Channels / metabolism*


  • Caenorhabditis elegans Proteins
  • FLR-1 protein, C elegans
  • Sodium Channels
  • Green Fluorescent Proteins
  • Protein Kinases
  • FLR-4 protein, C elegans
  • Protein-Serine-Threonine Kinases