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© by The Society for Leukocyte Biology
Journal of Leukocyte Biology, doi:10.1189/jlb.0205091

Received for publication February 14, 2005.

Accepted for publication March 10, 2005.

Article

Phosphoinositide-3 kinase regulates actin polymerization during delayed phagocytosis of Helicobacter pylori

Lee-Ann H. Allen @, J. Aaron Allgood , Xuemei Han , and Lara M. Wittine

Department of Medicine and the Inflammation Program, University of Iowa and the VA Medical Center, Iowa City

@ To whom correspondence should be addressed. E-mail: lee-ann-allen{at}uiowa.edu.


  Abstract

We have shown previously that ulcerogenic (type I) strains of Helicobacter pylori (Hp) retard their entry into macrophages. However, the signaling pathways that regulate Hp phagocytosis are largely undefined. We show here that Hp strongly activated class IA phosphoinositide-3 kinases (PI-3Ks) in macrophages, coincident with phagocytosis, and endogenous p85 and active protein kinase B{alpha} accumulated on forming phagosomes. PI-3K inhibitors, wortmannin and LY294002, inhibited phagocytosis of Hp in a dose-dependent manner, and blockade of engulfment correlated directly with loss of 3`-phosphoinositides in the membrane subjacent to attached bacteria. During uptake of large immunoglobulin G (IgG)-coated particles, PI-3Ks regulate pseudopod extension and phagosome closure. In marked contrast, we show here that 3`-phosphoinositides regulated actin polymerization at sites of Hp uptake. Moreover, Hp and IgG beads activated distinct PI-3K isoforms. Phagosomes containing IgG-coated particles accumulated 3`-phosphatase and tensin homologue deleted on chromosome 10 and Src homology 2 domain-containing inositol 5`-phosphatase, yet Hp phagosomes did not. Finally, rapid uptake of IgG-opsonized Hp or a less-virulent type II Hp was PI-3K-independent. We conclude that Hp and IgG beads are ingested by distinct mechanisms and that PI-3Ks regulate the actin cytoskeleton during slow phagocytosis of ulcerogenic Hp.

Key Words: macrophage • signal transduction • phagosome




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