ABSTRACT
Exogenous HIV-1 matrix protein p17 was found to deregulate biologic activities of many different immune cells that are directly or indirectly involved in AIDS pathogenesis after binding to unknown cellular receptor(s). In particular, p17 was found to induce a functional program in monocytes related to activation and inflammation. In the present study, we demonstrate that CXCR1 is the receptor molecule responsible for p17 chemokine-like activity on monocytes. After CXCR1 binding, p17 was capable of triggering rapid adhesion and chemotaxis of monocytes through a pathway that involved Rho/ROCK. Moreover, CXCR1-silenced primary monocytes lost responsiveness to p17 chemoattraction, whereas CXCR1-transfected Jurkat cells acquired responsiveness. Surface plasmon resonance studies confirmed the capacity of p17 to bind CXCR1 and showed that the p17/CXCR1 interaction occurred with a low affinity compared with that measured for IL-8, the physiologic CXCR1 ligand. In all of its activities, p17 mimicked IL-8, the natural high-affinity ligand of CXCR1. Recent studies have highlighted the role of IL-8 and CXCR1 in HIV-1 replication and AIDS pathogenesis. Our findings herein call for an exploration of the therapeutic potential of blocking the p17/IL-8/CXCR1 axis in HIV-1 infection.
Subject(s)
HIV Antigens/metabolism , Monocytes/metabolism , Receptors, Interleukin-8A/metabolism , gag Gene Products, Human Immunodeficiency Virus/metabolism , rho-Associated Kinases/metabolism , Animals , Binding, Competitive , Cell Adhesion/drug effects , Cell Movement/drug effects , Cells, Cultured , Chemotaxis, Leukocyte/drug effects , Dose-Response Relationship, Drug , Enzyme Activation , HIV Antigens/genetics , HIV Antigens/pharmacology , Humans , Interleukin-8/metabolism , Jurkat Cells , Male , Mice , Mice, Inbred C57BL , Monocytes/cytology , Monocytes/drug effects , Neutrophils/cytology , Neutrophils/drug effects , Neutrophils/metabolism , Pertussis Toxin/pharmacology , Protein Binding , RNA Interference , Receptors, Interleukin-8A/genetics , Recombinant Proteins/metabolism , Recombinant Proteins/pharmacology , gag Gene Products, Human Immunodeficiency Virus/genetics , gag Gene Products, Human Immunodeficiency Virus/pharmacologyABSTRACT
The HIV-1 matrix protein p17 is a structural protein that can act in the extracellular environment to deregulate several functions of immune cells, through the interaction of its NH(2)-terminal region with a cellular surface receptor (p17R). The intracellular events triggered by p17/p17R interaction have been not completely characterized yet. In this study we analyze the signal transduction pathways induced by p17/p17R interaction and show that in Raji cells, a human B cell line stably expressing p17R on its surface, p17 induces a transient activation of the transcriptional factor AP-1. Moreover, it was found to upregulate pERK1/2 and downregulate pAkt, which are the major intracellular signalling components involved in AP-1 activation. These effects are mediated by the COOH-terminal region of p17, which displays the capability of keeping PTEN, a phosphatase that regulates the PI3K/Akt pathway, in an active state through the serine/threonine (Ser/Thr) kinase ROCK. Indeed, the COOH-terminal truncated form of p17 (p17Δ36) induced activation of the PI3K/Akt pathway by maintaining PTEN in an inactive phosphorylated form. Interestingly, we show that among different p17s, a variant derived from a Ugandan HIV-1 strain, named S75X, triggers an activation of PI3K/Akt signalling pathway, and leads to an increased B cell proliferation and malignant transformation. In summary, this study shows the role of the COOH-terminal region in modulating the p17 signalling pathways so highlighting the complexity of p17 binding to and signalling through its receptor(s). Moreover, it provides the first evidence on the presence of a p17 natural variant mimicking the p17Δ36-induced signalling in B cells and displaying the capacity of promoting B cell growth and tumorigenesis.
Subject(s)
B-Lymphocytes/enzymology , B-Lymphocytes/pathology , HIV Antigens/metabolism , Mutant Proteins/metabolism , PTEN Phosphohydrolase/metabolism , gag Gene Products, Human Immunodeficiency Virus/metabolism , Amino Acid Sequence , Cell Proliferation , Cells, Cultured , Colony-Forming Units Assay , Enzyme Activation , Extracellular Signal-Regulated MAP Kinases/metabolism , HIV Antigens/chemistry , Humans , Molecular Sequence Data , Mutant Proteins/chemistry , Osmolar Concentration , Phosphorylation , Protein Binding , Protein Structure, Quaternary , Proto-Oncogene Proteins c-akt/metabolism , Receptors, Virus/metabolism , Sequence Alignment , Signal Transduction , Solutions , Transcription Factor AP-1/metabolism , gag Gene Products, Human Immunodeficiency Virus/chemistry , rho-Associated Kinases/metabolismABSTRACT
The success in the development of anti-retroviral therapies (HAART) that contain human immunodeficiency virus type 1 (HIV-1) infection is challenged by the cost of this lifelong therapy and by its toxicity. Immune-based therapeutic strategies that boost the immune response against HIV-1 proteins or protein subunits have been recently proposed to control virus replication in order to provide protection from disease development, reduce virus transmission, and help limit the use of anti-retroviral treatments. HIV-1 matrix protein p17 is a structural protein that is critically involved in most stages of the life cycle of the retrovirus. Besides its well established role in the virus life cycle, increasing evidence suggests that p17 may also be active extracellularly in deregulating biological activities of many different immune cells that are directly or indirectly involved in AIDS pathogenesis. Thus, p17 might represent a promising target for developing a therapeutic vaccine as a contribution to combating AIDS. In this article we review the biological characteristics of HIV-1 matrix protein p17 and we describe why a synthetic peptide representative of the p17 functional epitope may work as a vaccine molecule capable of inducing anti-p17 neutralizing response against p17 derived from divergent HIV-1 strains.
