Evidence for a Functional Receptor for Cyclosporin A on the Surface of Lymphocytes

• Published in: Proceedings of the National Academy of Sciences - PNAS 1992-05, Vol.89 (10), p.4353-4357
• Main Authors: Cacalano, Nicholas A., B.-X. Chen, Cleveland, W. Louis, Erlanger, Bernard F.
• Format: Article
• Language: English
• Subjects: Agglutination; Animals; B-Lymphocytes - metabolism; Biological and medical sciences; Cell Line; Cell Membrane - immunology; Cell Membrane - metabolism; Cell membranes; Cell surface receptors; Cellular biology; COS cells; Cyclosporine - metabolism; Cyclosporine - pharmacology; HeLa cells; Humans; Immunity (Disease); Immunomodulators; Immunosuppression; Interleukin-2 - metabolism; Kinetics; Lymphocytes - drug effects; Lymphocytes - immunology; Lymphocytes - metabolism; lymphocytes T; Medical research; Medical sciences; Mice; Ova; Pharmacology. Drug treatments; Receptors; Receptors, Immunologic - physiology; T lymphocytes; T-Lymphocytes - metabolism; Tetradecanoylphorbol Acetate - pharmacology
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.89.10.4353

Cyclosporin A (CsA) is an immunosuppressive agent that inhibits the synthesis of lymphokines by T lymphocytes at the level of transcription. A cytoplasmic protein, cyclophilin, is the most thoroughly studied CsA-binding protein, but its ubiquitous presence in cells of all types raises questions about its role in immunosuppression. In an attempt to ascertain the presence of a cell surface receptor, we synthesized two polyvalent macromolecular CsA derivatives, CsA-BBa-ovalbumin and CsA-BBa-aminodextran (CBD), from the product of the photochemical reaction of CsA and 4-benzoylbenzoic acid (CsA-BBa). (i) They inhibited the peptidylprolyl cis-trans isomerase activity of cyclophilin and the synthesis of interleukin 2 by phorbol ester-activated EL-4 cells. (ii) CBD also inhibited interleukin 2 secretion by Con A-activated T-cell-enriched mouse splenocytes. 4-Benzoylbenzoic acid (BBa)-aminodextran and aminodextran were inactive. (iii) Direct binding and competition studies with [3H]CsA indicated that CBD does not enter EL-4 cells (i.e., it acted at the surface). (iv) CBD caused agglutination of EL-4 cells, murine B and T lymphocytes, human thymocytes, and two T-cell hybridomas. Agglutination was inhibited by a monoclonal antibody to CsA and by CsA and CsA-BBa, but not by BBa. No agglutination was seen with BBa-aminodextran or aminodextran. HeLa cells, Vero (monkey kidney) cells, a mouse plasmacytoma, COS cells, and a poorly differentiated B-cell lymphoma were not agglutinated. (v) EL-4 cells failed to be agglutinated after treatment with trypsin or chymotrypsin. Specific agglutination was again possible after incubation for 5 h at 37⚬C in the absence of enzyme. (vi) CBD covalently linked to crosslinked agarose beads inhibited interleukin 2 production by phorbol ester-stimulated EL-4 cells. No activity was seen if cell-to-bead contact was prevented by a 0.02-μ m microporous filter that did not interfere with the passage of CBD. Our findings support the presence of a functional receptor on the surface of selected cells of the immune system.