HIV-1 Nef Inhibits Lipopolysaccharide-induced IL-12p40 Expression by Inhibiting JNK-activated NFκB in Human Monocytic Cells

Wei Ma,Sasmita Mishra,Niranjala Gajanayaka,Jonathan B Angel,Ashok Kumar

doi:10.1074/jbc.m710013200

Abstract

Impaired cellular immunity caused by decreased production of Th1-type cytokines, including interleukin-12 (IL-12) is a major feature of HIV-1-associated immunodeficiency and acquired immunodeficiency syndrome. IL-12p40, an inducible subunit shared between IL-12 and IL-23, plays a critical role in the development of cellular immunity, and its production is significantly decreased during HIV infection. The mechanism by which HIV induces loss of IL-12p40 production remains poorly understood. We have previously shown that lipopolysaccharide (LPS)-induced IL-12p40 production in monocytic cells is regulated by NFkappaB and AP-1 transcription factors through the activation of two distinct upstream signaling pathways, namely the c-Jun-N-terminal kinase (JNK) and the calmodulin-dependent protein kinase-II-activated pathways. Herein, we show that intracellular nef expressed through transduction of primary monocytes and promonocytic THP-1 cells with retroviral-mediated nef gene inhibited LPS-induced IL-12p40 transcription by inhibiting the JNK mitogen-activated protein kinases without affecting the calmodulin-dependent protein kinase-II-activated pathway. In addition, nef inhibited JNK-activated NFkappaB without affecting the AP-1 activity. Overall, our results suggest for the first time that intracellular nef inhibited LPS-activated JNK, which may cause inhibition of IL-12p40 expression in human monocytic cells by selectively inhibiting NFkappaB activity.

Highlights

Impaired cellular immunity caused by decreased production of Th1-type cytokines, including interleukin-12 (IL-12) is a major feature of HIV-1-associated immunodeficiency and acquired immunodeficiency syndrome
Our results suggest for the first time that intracellular nef inhibited LPS-activated Jun-N-terminal kinase (JNK), which may cause inhibition of IL-12p40 expression in human monocytic cells by selectively inhibiting NF␬B activity
We show for the first time that intracellular expression of HIV-nef by retroviral infection of primary monocytes and promonocytic THP-1 cells and following stable transfection of THP-1 cells with HIV-nef gene resulted in the inhibition of LPS-induced IL-12p40 production

Summary

Introduction

Impaired cellular immunity caused by decreased production of Th1-type cytokines, including interleukin-12 (IL-12) is a major feature of HIV-1-associated immunodeficiency and acquired immunodeficiency syndrome. We have previously shown that lipopolysaccharide (LPS)-induced IL-12p40 production in monocytic cells is regulated by NF␬B and AP-1 transcription factors through the activation of two distinct upstream signaling pathways, namely the c-Jun-N-terminal kinase (JNK) and the calmodulin-dependent protein kinase-II-activated pathways. IL-12 acts as a bridge between innate and adaptive immune responses and plays a critical role in the immunopathogenesis of various diseases, including HIV infection, inflammation, and autoimmune disorders [3, 4, 6, 7] It promotes Th1-type cell-mediated immune responses by inducing interferon-␥ from NK and T cells and enhances their cytotoxicity [7, 8]. Active cellular infection and HIV replication inhibited IL-12p40 transcription and its synthesis in monocytic mitogen-activated protein kinase; pSR␣, the retrovirus containing the empty vector; pSR␣-Nef, pSR␣ containing the Nef gene; SEK1, stress-activated protein kinase/extra-cellular signal-regulated kinase 1

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Conclusion