Disruption of Dictyostelium PI3K genes reduces [32P]phosphatidylinositol 3,4 bisphosphate and [32P]phosphatidylinositol trisphosphate levels, alters F-actin distribution and impairs pinocytosis

J Cell Sci. 1998 Jan:111 ( Pt 2):283-94. doi: 10.1242/jcs.111.2.283.

Abstract

To understand how phosphatidylinositol 3-kinase (PI3K) modulates cell structure and function, we examined the molecular and cellular defects of a Dictyostelium mutant strain (pik1(Delta)2(Delta)) missing two (DdPIK1 and 2) of three PI3K genes, which are homologues of the mammalian p110 subunit. Levels of [32P]phosphatidylinositol 3, 4 bisphosphate (PI(3,4)P2) and [32P]phosphatidylinositol trisphosphate (PIP3) were reduced in pik1(Delta)2(Delta), which had major defects in morphological and functional correlates of macropinocytosis. This was accompanied by dramatic deficits in a subset of F-actin-enriched structures such as circular ruffles, actin crowns and pseudopodia. Although pik1(Delta)2(Delta) were mobile, they failed to aggregate into streams. Therefore we conclude that PIK1 and 2, possibly through modulation of the levels of PIP3 and PI(3,4)P2, regulate the organization of actin filaments necessary for circular ruffling during macropinocytosis, the extension of pseudopodia and the aggregation of cells into streams, but not the regulation of cell motility.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actins / metabolism*
  • Animals
  • Cell Movement
  • Dictyostelium / genetics
  • Dictyostelium / metabolism*
  • Genetic Complementation Test
  • Mutagenesis
  • Phagocytosis
  • Phosphatidylinositol 3-Kinases / genetics
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphatidylinositol Phosphates / metabolism*
  • Phosphorus Radioisotopes
  • Pinocytosis / physiology*
  • Vacuoles

Substances

  • Actins
  • Phosphatidylinositol Phosphates
  • Phosphorus Radioisotopes
  • phosphatidylinositol 3,4,5-triphosphate
  • phosphatidylinositol 3,4-diphosphate
  • Phosphatidylinositol 3-Kinases