Published online before print May 27, 2005
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* Institute of Human Virology, University of Maryland Biotechnology Institute, and
Department of Microbiology and Immunology, School of Medicine, University of Maryland, Baltimore; and
Chemocentryx, Inc., Mt. View, California
1 Correspondence: Institute of Human Virology, University of Maryland Biotechnology Institute, University of Maryland, 725 W. Lombard Street, Baltimore, MD 21201. E-mail: devico{at}umbi.umd.edu
The CC chemokine regulated on activation, normal T cell expressed and secreted (RANTES)/CC chemokine ligand 5 (CCL5) is expressed by macrophages, endothelial cells, keratinocytes, and T cells during a wide variety of immune responses. Post-translational proteolysis is expected to play an important role in regulating such broad-based expression; however, the rates and modes of RANTES processing by primary cell systems remain poorly understood. Here, we show that peripheral blood mononuclear cells (PBMC) secrete RANTES as an intact molecule that is subject to three post-translational processing pathways. One occurs in the presence of serum or plasma and rapidly generates a RANTES variant lacking two N-terminal residues (368 RANTES). Such processing is mainly attributable to soluble CD26. A second pathway, which is evident in the absence of serum or plasma, generates 368 RANTES in concert with the expression of cell-surface CD26. The third pathway is unique and generates a novel variant lacking three N-terminal residues (468 RANTES). This variant binds CC chemokine receptor 5, exhibits reduced chemotactic and human immunodeficiency virus (HIV)-suppressive activity compared with 168 and 368 RANTES, and is generated by an unidentified enzyme associated with monocytes and neutrophils. Overall, these results indicate that the production of RANTES by primary cells is regulated by multiple processing pathways which produce two variants with different functional properties. Such findings have important implications for understanding the immunological and HIV-suppressive activities of native RANTES.
Key Words: chemokines CD26 protease PBMC
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