CD2 physically associates with CD5 in rat T lymphocytes with the involvement of both extracellular and intracellular domains

• Published in: European journal of immunology 2002-05, Vol.32 (5), p.1509-1518
• Main Authors: Castro, Mónica A. A., Tavares, Paula A., Almeida, Mara S., Nunes, Raquel J., Wright, Mark D., Mason, Don, Moreira, Alexandra, Carmo, Alexandre M.
• Format: Article
• Language: English
• Subjects: Animals; CD2; CD2 Antigens - chemistry; CD2 Antigens - genetics; CD2 Antigens - metabolism; CD4 Antigens - metabolism; CD5; CD5 Antigens - chemistry; CD5 Antigens - genetics; CD5 Antigens - metabolism; Cell Line; COS Cells; Extracellular Space - immunology; Immunologic Capping; In Vitro Techniques; Intracellular Fluid - immunology; Male; Precipitin Tests; Protein Structure, Tertiary; Rats; Recombinant Fusion Proteins - chemistry; Recombinant Fusion Proteins - genetics; Recombinant Fusion Proteins - metabolism; Signal Transduction; T lymphocyte; T-Lymphocytes - immunology; Transfection
• ISSN: 0014-2980; 1521-4141
• DOI: 10.1002/1521-4141(200205)32:5<1509::AID-IMMU1509>3.0.CO;2-T

T lymphocytes can be activated and induced to proliferate through stimulation of the CD2 glycoprotein with functional combinations of CD2 antibodies. However, this mechanism of signal transduction via CD2 is still not fully understood. We have investigated which molecules on the T cell surface preferentially associate in Cis with CD2 and may regulate its signaling properties. Though a quantification method we found that CD5 represents the antigen capable of co‐precipitating a larger proportion of CD2. Using co‐capping assays and immunoprecipitations from cell lysates, we show that an association between CD2 and CD5 can be found in rat thymocytes, T lymphocytes and in a thymoma cell line. Possibly, this interaction is a direct one, since CD2 and CD5 transiently expressed in Cos7 cells co‐precipitate each other. Furthermore, using CD2 chimeric proteins containing different domains of CD2, expressed in Cos7 cells as well as in stably transfected Jurkat cells, we show that the interaction between CD2 and CD5 is held at both the intra‐ and extracellular levels, but does not involve the transmembrane domain. The fact that both the extracellular and the cytoplasmic domains of CD2 interact with CD5 suggests a specific and tight association between the two molecules, possibly relevant for the fine‐tuning of signal transduction in T lymphocytes.