Class IA phosphoinositide 3-kinase β and δ regulate neutrophil oxidase activation in response to Aspergillus fumigatus hyphae

J Immunol. 2011 Mar 1;186(5):2978-89. doi: 10.4049/jimmunol.1002268. Epub 2011 Jan 21.

Abstract

An effective immune response to the ubiquitous fungus Aspergillus fumigatus is dependent upon production of reactive oxygen species (ROS) by the NADPH oxidase. This is evidenced by the acute sensitivity of oxidase-deficient humans and mice to invasive aspergillosis. Neutrophils are recruited to the lungs shortly postinfection and respond by phagocytosing conidia and mediating extracellular killing of germinated hyphae in a ROS-dependent manner. However, the signaling mechanisms regulating the generation of ROS in response to hyphae are poorly understood. PI3Ks are important regulators of numerous cellular processes, with much recent work describing unique roles for the different class I PI3K isoforms. We showed by live-cell imaging that the lipid products of class I PI3Ks accumulated at the hyphal-bound neutrophil plasma membrane. Further, we used pharmacological and genetic approaches to demonstrate essential, but overlapping, roles for PI3Kβ and PI3Kδ in the ROS and spreading responses of murine neutrophils to Aspergillus hyphae. Hyphal-induced ROS responses were substantially inhibited by deletion of the common β2-integrin subunit CD18, with only a minor, redundant role for Dectin-1. However, addition of soluble algal glucans plus the genetic deletion of CD18 were required to significantly inhibit activation of the PI3K-effector protein kinase B. Hyphal ROS responses were also totally dependent on the presence of Syk, but not its ITAM-containing adaptor proteins FcRγ or DAP12, and the Vav family of Rac-guanine nucleotide exchange factors. These results start to define the signaling network controlling neutrophil ROS responses to A. fumigatus hyphae.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Aspergillus fumigatus / enzymology
  • Aspergillus fumigatus / immunology*
  • Aspergillus fumigatus / metabolism
  • Catalytic Domain / immunology
  • Cell Adhesion / immunology
  • Class I Phosphatidylinositol 3-Kinases
  • Class Ia Phosphatidylinositol 3-Kinase / physiology*
  • Enzyme Activation / genetics
  • Enzyme Activation / immunology
  • Hyphae / enzymology
  • Hyphae / immunology*
  • Isoenzymes / deficiency
  • Isoenzymes / genetics
  • Isoenzymes / physiology
  • Mice
  • Mice, 129 Strain
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Mice, Transgenic
  • NADPH Oxidases / metabolism*
  • Neutrophil Activation / genetics
  • Neutrophil Activation / immunology*
  • Neutrophils / enzymology*
  • Neutrophils / immunology
  • Neutrophils / microbiology
  • Phosphatidylinositol 3-Kinases / physiology*
  • Protein Subunits / deficiency
  • Protein Subunits / genetics
  • Protein Subunits / physiology*
  • Radiation Chimera
  • Reactive Oxygen Species / metabolism
  • Signal Transduction / genetics
  • Signal Transduction / immunology

Substances

  • Isoenzymes
  • Protein Subunits
  • Reactive Oxygen Species
  • NADPH Oxidases
  • Class I Phosphatidylinositol 3-Kinases
  • Class Ia Phosphatidylinositol 3-Kinase
  • Pik3cd protein, mouse