A biologic function for an "orphan" messenger: D-myo-inositol 3,4,5,6-tetrakisphosphate selectively blocks epithelial calcium-activated chloride channels.

Academic Article

Abstract

  • Inositol phosphates are a family of water-soluble intracellular signaling molecules derived from membrane inositol phospholipids. They undergo a variety of complex interconversion pathways, and their levels are dynamically regulated within the cytosol in response to a variety of agonists. Relatively little is known about the biological function of most members of this family, with the exception of inositol 1,4,5-trisphosphate. Specifically, the biological functions of inositol tetrakisphosphates are largely obscure. In this paper, we report that D-myo-inositol 3,4,5,6-tetrakisphosphate (D-Ins(3,4,5,6)P4) has a direct biphasic (activation/inhibition) effect on an epithelial Ca(2+)-activated chloride channel. The effect of D-Ins(3,4,5,6)P4 is not mimicked by other inositol tetrakisphosphate isomers, is dependent on the prevailing calcium concentration, and is influenced when channels are phosphorylated by calmodulin kinase II. The predominant effect of D-Ins(3,4,5,6)P4 on phosphorylated channels is inhibitory at levels of intracellular calcium observed in stimulated cells. Our findings indicate the biological function of a molecule hitherto considered as an "orphan" messenger. They suggest that the molecular target for D-Ins(3,4,5,6)P4 is a plasma membrane Ca(2+)-activated chloride channel. Regulation of this channel by D-Ins(3,4,5,6)P4 and Ca2+ may have therapeutic implications for the disease states of both diabetic nephropathy and cystic fibrosis.
  • Keywords

  • Adenosine Triphosphate, Animals, Calcium, Calcium-Calmodulin-Dependent Protein Kinase Type 2, Calcium-Calmodulin-Dependent Protein Kinases, Calmodulin, Cattle, Chloride Channels, Cloning, Molecular, Egtazic Acid, Epithelium, Female, Inositol Phosphates, Lipid Bilayers, Membrane Potentials, Oocytes, Recombinant Proteins, Signal Transduction, Xenopus laevis
  • Author List

  • Ismailov II; Fuller CM; Berdiev BK; Shlyonsky VG; Benos DJ; Barrett KE
  • Start Page

  • 10505
  • End Page

  • 10509
  • Volume

  • 93
  • Issue

  • 19