The Abl and Arg Kinases Mediate Distinct Modes of Phagocytosis and Are Required for Maximal Leishmania Infection

Abstract

Leishmania, an obligate intracellular parasite, binds several receptors to trigger engulfment by phagocytes, leading to cutaneous or visceral disease. These receptors include complement receptor 3 (CR3), used by promastigotes, and the Fc receptor (FcR), used by amastigotes. The mechanisms mediating uptake are not well understood. Here we show that Abl family kinases mediate both phagocytosis and the uptake of Leishmania amazonensis by macrophages (Mϕs). Imatinib, an Abl/Arg kinase inhibitor, decreases opsonized polystyrene bead phagocytosis and Leishmania uptake. Interestingly, phagocytosis of IgG-coated beads is decreased in Arg-deficient Mϕs, while that of C3bi-coated beads is unaffected. Conversely, uptake of C3bi-coated beads is decreased in Abl-deficient Mϕs, but that of IgG-coated beads is unaffected. Consistent with these results, Abl-deficient Mϕs are inefficient at C3bi-opsonized promastigote uptake, and Arg-deficient Mϕs are defective in IgG1-opsonized amastigote uptake. Finally, genetic loss of Abl or Arg reduces infection severity in murine cutaneous leishmaniasis, and imatinib treatment results in smaller lesions with fewer parasites than in controls. Our studies are the first to demonstrate that efficient phagocytosis and maximal Leishmania infection require Abl family kinases. These results highlight Abl family kinase-mediated signaling pathways as potential therapeutic targets for leishmaniasis.

ACKNOWLEDGMENTS

We thank Norma Andrews for providing L. amazonensis strain IFLA/BR/67/PH8 and Richard Flavell for providing Tie2-Cre⁺ mice. The M1/70 antibody was obtained from the Developmental Studies Hybridoma Bank, developed under the NICHD and maintained by the University of Iowa, Iowa City, IA. We thank all of the members of the McMahon-Pratt and Koleske laboratories, as well as Hanspeter Niederstrasser, for technical assistance, helpful discussions, and critical comments on the manuscript. We also thank the Calderwood laboratory for helpful discussions and use of their Amaxa nucleofector device.

D.M.W. was supported by T32 AI007210, a Pediatric Infectious Diseases Society Fellowship (sponsored by Wyeth Pharmaceuticals), and NRSA F32 AI094905. Work was supported by PHS grants CA133346, NS39475 (A.J.K.), and AI093775 (D.M.P.).