Proteasome-mediated Degradation of STAT1α following Infection of Macrophages with Leishmania donovani

• Published in: The Journal of biological chemistry Vol. 280; no. 34; pp. 30542 - 30549
• Main Authors: Forget, Geneviève, Gregory, David J., Olivier, Martin
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 26.08.2005
• Subjects: Leishmania donovani; Trypanosoma cruzi
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M414126200

Activation of the Janus-activated kinase 2 (JAK2)/STAT1α signaling pathway is repressed in Leishmania-infected macrophages. This represents an important mechanism by which this parasite subverts the microbicidal functions of the cell to promote its own survival and propagation. We recently provided evidence that the protein tyrosine phosphatase (PTP) SHP-1 was responsible for JAK2 inactivation. However, STAT1 translocation to the nucleus was not restored in the absence of SHP-1. In the present study, we have used B10R macrophages to study the mechanism by which this Leishmania-induced STAT1 inactivation occurs. STAT1α nuclear localization was shown to be rapidly reduced by the infection. Western blot analysis revealed that cellular STAT1α, but not STAT3, was degraded. Using PTP inhibitors and an immortalized bone marrow-derived macrophage cell line from SHP-1-deficient mice, we showed that STAT1 inactivation was independent of PTP activity. However, inhibition of macrophage proteasome activity significantly rescued Leishmania-induced STAT1α degradation. We further demonstrated that degradation was receptor-mediated and involved protein kinase Cα. All Leishmania species tested (L. major, L. donovani, L. mexicana, L. braziliensis), but not the related parasite Trypanosoma cruzi, caused STAT1α degradation. Collectively, results from this study revealed a new mechanism for STAT1 regulation by a microbial pathogen, which favors its establishment and propagation within the host.