Thy-1 functions as a signal transduction molecule in T lymphocytes and transfected B lymphocytes

Abstract

Thy-1, a glycoprotein of relative molecular mass 25,000 (25K), is a major constituent of the cell surface of mouse thymocytes, peripheral T cells and neurones¹. In man, Thy-1 is present on neurones and on a small percentage of thymocytes, but is absent from peripheral T cells². The amino-acid^3,4 and complementary DNA^5–7 sequences of Thy-1 indicate that it has a structure similar to an isolated V (variable region) domain of immunoglobulin⁴. Although the function of Thy-1 is unknown, the ability of different anti-Thy-1 monoclonal antibodies to activate murine T cells^8,9 or induce functional changes in neuronal cells in vitro¹⁰ suggests that Thy-1 is involved in transmembrane signalling. We now show that crosslinking of murine Thy-1 triggers a rapid rise in the cytoplas-mic free calcium concentration ([Ca²⁺]_i), not only in murine T cells and Thy-1.2-transfected human T cells, but also in murine B-lymphoma cells transfected with the murine thy-1.2 gene. These results indicate that the generation and transduction of the signal leading to the rise in [Ca²⁺]_i is independent of the T-cell receptor and other T-cell-spec i fie molecules. The preservation of the [Ca²⁺]_i-modulating function of Thy-1 in various lymphoid cells of two species further suggests that the necessary signal either originates in the Thy-1 molecule itself or is generated in concert with a highly conserved molecules(s) associated with Thy-1.