Polarized subcellular distribution of the 1-, 4- and 5-phosphatase activities that metabolize inositol 1,4,5-trisphosphate in intestinal epithelial cells

Biochem J. 1990 Jul 15;269(2):353-8. doi: 10.1042/bj2690353.

Abstract

In intestinal epithelial cells, Ins(1,4,5)P3 is metabolized both by an intracellular 5-phosphatase and by less specific extracellular phosphatases [Rubiera, Velasco, Michell, Lazo & Shears (1988) Biochem. J. 255, 131-137]. A total of 91% of intracellular Ins(1,4,5)P3 5-phosphatase was particulate, and was preferentially associated with plasma membranes rather than with other subcellular organelles. A soluble Ins(1,4,5)P3 3-kinase activity was also characterized, further supporting the idea that inositol phosphates are important in enterocyte function. We have studied the distribution of Ins(1,4,5)P3 phosphatase activities in basolateral and brush-border domains of the plasma membrane. Compared with homogenates, the extracellular phosphatases were 13-17-fold enriched in brush-border membranes, but only 2-fold enriched in basolateral membranes. The 1- and 4-phosphates of Ins(1,4,5)P3 were hydrolysed at equal rates by the extracellular phosphatases; these enzymes are proposed to have digestive functions. The intracellular particulate 5-phosphatase was 2-fold enriched in brush-border membranes and 13-fold enriched in basolateral membranes, at the same pole of the cell where Ins(1,4,5)P3 is believed to be generated. This is opposite to the polarized distribution of particulate 5-phosphatase in hepatocytes [Shears, Evans, Kirk & Michell (1988) Biochem. J. 256, 363-369]; these differences in subcellular distribution may be important in determining cell-specific metabolism of Ins(1,4,5)P3.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Membrane / enzymology
  • Chromatography, High Pressure Liquid
  • Epithelium / enzymology
  • Epithelium / ultrastructure
  • Glucose-6-Phosphate
  • Glucosephosphates / pharmacology
  • Hydrogen-Ion Concentration
  • Inositol 1,4,5-Trisphosphate / metabolism*
  • Inositol Polyphosphate 5-Phosphatases
  • Intestines / enzymology
  • Intestines / ultrastructure*
  • Microvilli / enzymology
  • Phosphoric Monoester Hydrolases / analysis*
  • Phosphoric Monoester Hydrolases / metabolism
  • Phosphorylation
  • Phosphotransferases (Alcohol Group Acceptor)*
  • Phosphotransferases / analysis
  • Rats
  • Rats, Inbred Strains
  • Subcellular Fractions / enzymology*

Substances

  • Glucosephosphates
  • Glucose-6-Phosphate
  • Inositol 1,4,5-Trisphosphate
  • Phosphotransferases
  • Phosphotransferases (Alcohol Group Acceptor)
  • Inositol 1,4,5-trisphosphate 3-kinase
  • Phosphoric Monoester Hydrolases
  • Inositol Polyphosphate 5-Phosphatases