Molecular Immunology 46 (2009) 2947–2954 Contents lists available at ScienceDirect Molecular Immunology journal homepage: www.elsevier.com/locate/molimm SOCS3 expression induced by PIM2 requires PKC and PI3K signaling Yeddula Narayana a , Kushagra Bansal a , Akhauri Yash Sinha a , Nisha Kapoor a , Germain Puzo b , Martine Gilleron b , Kithiganahalli Narayanaswamy Balaji a,∗ a Department of Microbiology and Cell Biology, Indian Institute of Science, Bangalore 560012, India b Department of Molecular Mechanisms of Mycobacterial Infections, Institut de Pharmacologie et de Biologie Structurale du Centre National de la Recherche Scientifique (CNRS) and Université Paul Sabatier, 205 route de Narbonne, 31077 Toulouse Cedex 4, France article info Article history: Received 6 May 2009 Received in revised form 11 June 2009 Accepted 18 June 2009 Available online 15 July 2009 Keywords: PIM2 TLR2 SOCS3 PI3K PKC abstract Initiation of proinflammatory host immunity in response to infection represents as a key event in effective control and containment of the pathogen at the site of infection as well as in elicitation of robust immune memory responses. In the current investigation, we demonstrate that an integral cell wall antigen of the mycobacterial envelope, Phosphatidyl-myo-inositol dimannosides (PIM2) triggers Suppressor of cytokine signaling (SOCS) 3 expression in macrophages in a Toll-like receptor 2 (TLR2)-MyD88 dependent manner. Data derived from signaling perturbations suggest the involvement of phosphoinositide-3 kinase (PI3K) and protein kinase C (PKC) signaling pathways during PIM2 induced SOCS3 expression. Further, pharma- cological inhibition of ERK1/2, but not of p38 MAP kinase or JNK abrogated the induced expression of SOCS3. The PIM2 induced activation of ERK1/2 was dependent on the activation of PI3K or PKC signal- ing which in turn regulated p65 nuclear factor -B (NF-B) nuclear translocation. Overall, current study delineates the role for PI3K-PKC axis and ERK1/2 signaling as key signaling events during PIM2 induced SOCS3 expression in macrophages. © 2009 Elsevier Ltd. All rights reserved. 1. Introduction Macrophages play a central role in pathophysiological responses associated with infections with various mycobacteria including Mycobacterium tuberculosis, Mycobacterium bovis etc. Studies have suggested that macrophages participate in host immunity to intracellular mycobacterial infections by modulating the steps of initiation as well as the activation of host proinflammatory responses (Flynn and Chan, 2001). The regulation of proinflam- matory responses often involves diverse signaling cascades and modulation of key signaling cascades leading to macrophage activa- tion represents one such mechanism by which mycobacteria might survive amid strong host immunity (Nigou et al., 2002; Schorey and Cooper, 2003; Koul et al., 2004; Jo et al., 2007; Pathak et al., 2007). In this perspective, selective refractoriness of mycobacteria infected macrophages to key cytokines including IFN- assumes critical importance in overall host immune responses. In this context, SOCS3, a member of SOCS family functions as negative regulator of several cytokine and toll receptor induced signaling (Yoshimura et al., 2007) and SOCS3 has been shown to specifically inhibit signal- ing by IFN-, IL-6 family of cytokines (Stoiber et al., 1999; Karlsen et al., 2001; Lang et al., 2003; Wormald et al., 2006). Diverse species of ∗ Corresponding author. Tel.: +91 80 22933223; fax: +91 80 23602697. E-mail address: balaji@mcbl.iisc.ernet.in (K.N. Balaji). mycobacteria including M. bovis BCG triggers the inducible expres- sion of SOCS3 (Imai et al., 2003; Manca et al., 2005; Vazquez et al., 2006; Narayana and Balaji, 2008). The induced expression of SOCS3 or SOCS1 proteins is suggested to play a role in marked reduc- tion in IFN--stimulated JAK/STAT signaling in macrophages (Imai et al., 2003). Despite the role of JAK/STAT signaling pathway, we and others have shown that STAT-independent signals including Notch1-PI3K signaling participate in the induction of SOCS proteins signifying the involvement of multiple signal events in regulation of SOCS expression (Cassatella et al., 1999; Narayana and Balaji, 2008). Albeit members of mycobacteria species are suggested to trig- ger SOCS3 expression, role of important cell wall antigens that contribute to mycobacterium potential to trigger SOCS3 expres- sion remains obscure. In this context, our current investigation focuses on PIM2, a key cell wall antigen present in mycobacteria. PIM represents a variety of phosphatidyl-myo-inositol mannosides (PIM) 1–6 containing molecules and are integral component of the mycobacterial envelope. Though mycobacteria reside within phagolysosomes of the infected macrophages, envelope gly- coconjugates like phosphatidyl-myo-inositol mannosides (PIM), Lipoarabinomannan (LAM), Trehalose 6,6 ′ -dimycolate (TDM; cord factor) etc., are released and traffic out of the mycobacterial phago- some into endocytic compartments as well as can gain access to the extracellular environment in the form of exocytosed vesicles (Beatty et al., 2000; Rhoades et al., 2003). A number of biological functions have been credited to PIM2 (Hoppe et al., 1997; Gilleron 0161-5890/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.molimm.2009.06.019