Fibronectin on activated T lymphocytes is bound to gangliosides and is present in detergent insoluble microdomains

Fibronectin (FN) is a multifunctional extracellular matrix glycoprotein, which participates in cell migration and signalling to adhering cells. Due to alternative splicing and post-translational modifications, different isoforms of FN are generated by a wide variety of cells. T lymphocytes synthesize a surface-associated isoform of FN, containing the two 'extradomains' FDA and EDB. In the present study, we identified gangliosides within the T-cell membrane as specific binding sites for the N-terminal 30 kDa fragment of FN. When T cells were activated with anti-CD3 coated beads, FN, together with the ganglioside GM 1, converged at the contact zone. Moreover, endogenous FN was present in the detergent insoluble microdomain. The function of FN in T cells is still under investigation; however, its presence together with gangliosides at the activation site suggests participation in T-cell signalling.