Immunocompetent astrocytes and microglia display major differences in the processing of the invariant chain and in the expression of active cathepsin L and cathepsin S

• Published in: European journal of immunology Vol. 31; no. 6; pp. 1813 - 1824
• Main Authors: Gresser, Olivia, Weber, Ekkehard, Hellwig, Andrea, Riese, Sigrid, Régnier‐Vigouroux, Anne
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY‐VCH Verlag GmbH 01.06.2001
• Subjects: Antigen presentation; Antigen Presentation - drug effects; Antigen Presentation - immunology; Antigens, Differentiation, B-Lymphocyte - immunology; Astrocytes - cytology; Astrocytes - drug effects; Astrocytes - immunology; Cathepsin; Cathepsin L; Cathepsins - immunology; Cells, Cultured; Cysteine Endopeptidases; Cytokine; Endopeptidases; Endosomes - ultrastructure; g-Interferon; Glial cell; Histocompatibility Antigens Class II - immunology; Humans; Immunocompetence; Interferon-gamma - immunology; Interferon-gamma - pharmacology; Invariant chain; Lysosomes - ultrastructure; Microglia - cytology; Microglia - drug effects; Microglia - immunology; Tumor Necrosis Factor-alpha - immunology; Tumor Necrosis Factor-alpha - pharmacology
• ISSN: 0014-2980; 1521-4141
• DOI: 10.1002/1521-4141(200106)31:6<1813::AID-IMMU1813>3.0.CO;2-8

The role of astrocytes and microglia as antigen‐presenting cells in the brain is still controversial. In this study we have analyzed and compared aspects of the molecular machinery that underlies MHC class II trafficking in immunocompetent astrocytes and microglia. We show that IFN‐γ‐stimulated microglia possess active cathepsin L and cathepsin S, and efficiently degrade the invariant chain, unlike IFN‐γ‐stimulated astrocytes that express cathepsin L but not cathepsin S. The lack of cathepsin S proves to be dramatic for the antigen‐presentation capacity of astrocytes, whichis nearly abolished when these cells are stimulated by a combination of IFN‐γ and TNF‐α. TNF‐α indeed decreases cathepsin L activity as we show here, leading to alterations in invariantchain processing, and hence in MHC class II trafficking in astrocytes. Cystatin C inhibits cathepsin L activity in astrocytes, but does not regulate cathepsin L and cathepsin S activity in microglia. We therefore identify cathepsin L and cathepsin S as key components in the regulation of the immune potential of astrocytes and microglia, and provide evidence for a cell‐specific regulation exerted byIFN‐γ and TNF‐α on the expression and activity of cathepsins.