p110-Related PI 3-kinases regulate phagosome-phagosome fusion and phagosomal pH through a PKB/Akt dependent pathway in Dictyostelium

Adam C. Rupper, Juan M. Rodriguez-Paris, Bryon D. Grove, James A. Cardelli

Research output: Contribution to journalArticle

33 Scopus citations

Abstract

The Dictyostelium p110-related PI 3-kinases, PIK1 and PIK2, regulate the endosomal pathway and the actin cytoskeleton, but do not significantly regulate internalization of particles in D. discoideum. Bacteria internalized into δdpik1/ddpik2 cells or cells treated with PI 3-kinase inhibitors remained intact as single particles in phagosomes with closely associated membranes after 2 hours of internalization, while in control cells, bacteria appeared degraded in multi-particle spacious phagosomes. Addition of LY294002 to control cells, after 60 minutes of chase, blocked formation of spacious phagosomes, suggesting PI 3-kinases acted late to regulate spacious phagosome formation. Phagosomes purified from control and drug treated cells contained equivalent levels of lysosomal proteins, including the proton pump complex, and were acidic, but in drug treated cells and δdpik1/ddpik2 cells phagosomal pH was significantly more acidic during maturation than the pH of control phagosomes. Inhibition of phagosomal maturation by LY294002 was overcome by increasing phagosomal pH with NH4Cl, suggesting that an increase in pH might trigger homotypic phagosome fusion. A pkbA null cell line (PKB/Akt) reproduced the phenotype described for cells treated with PI 3-kinase inhibitors and δdpik1/ddpik2 cells. We propose that PI 3-kinases, through a PKB/Akt dependent pathway, directly regulate homotypic fusion of single particle containing phagosomes to form multiparticle, spacious phagosomes, possibly through the regulation of phagosomal pH.

Original languageEnglish (US)
Pages (from-to)1283-1295
Number of pages13
JournalJournal of cell science
Volume114
Issue number7
Publication statusPublished - May 17 2001

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Keywords

  • 3-kinase
  • Dictyostelium discoideum
  • Phagosomal maturation
  • Phagosome fusion
  • Phosphoinositide
  • Protein kinase B

ASJC Scopus subject areas

  • Cell Biology

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