Syndecan‐2 can promote clearance of T‐cell receptor/CD3 from the cell surface

• Published in: Immunology 2012-11, Vol.137 (3), p.214-225
• Main Authors: Rovira‐Clavé, Xavier, Angulo‐Ibáñez, Maria, Noguer, Oriol, Espel, Enric, Reina, Manuel
• Format: Article
• Language: English
• Subjects: CD3 Complex - immunology; Down-Regulation; endocytosis; Humans; Jurkat Cells; Original; Receptors, Antigen, T-Cell - immunology; syndecan; Syndecan-2 - immunology; T cell receptors; T lymphocytes; T‐cell receptor down‐regulation; T‐cell receptor ζ chain
• ISSN: 0019-2805; 1365-2567
• DOI: 10.1111/j.1365-2567.2012.03626.x

Summary T cells express the heparan sulphate proteoglycans syndecan‐2 and syndecan‐4. Syndecan‐4 plays a T‐cell inhibitory role; however, the function of syndecan‐2 is unknown. In an attempt to examine this function, syndecan‐2 was expressed constitutively in Jurkat T cells. Interestingly, the expression of syndecan‐2 decreased the surface levels of T‐cell receptor (TCR)/CD3 complex, concomitant with intracellular retention of CD3ε and partial degradation of the TCR‐ζ chain. Immunofluorescence microscopy revealed that intracellular CD3ε co‐located with Rab‐4 endosomes. However, the intracellular pool of CD3ε did not recycle to the cell surface. The lower TCR/CD3 surface levels caused by syndecan‐2 led to reduced TCR/CD3 responsiveness. We show that the cytosolic PDZ‐binding domain of syndecan‐2 is not necessary to elicit TCR/CD3 down‐regulation. These results identify a previously unrecognized means of controlling surface TCR/CD3 expression by syndecan‐2.