Expression, Distribution And Function Of PTA1 Molecule, A Novel Member Of Immunoglobulinsuperfamily, On Human Megakaryocyte/platelet Lineage

The PTA1 antigen was initially discribed as a T lineage specific activation antigen expressed mainly on the surface of activation T cells and involved in the differentiation of human cytotoxic T cells in 1985 with the name TLiSA1(T lineage specific activation antigen 1). Subsequently the antigen was identified on platelets and involved in platelet activation and renamed platelet and T cell activation antigenl (PTA1). Furthermore preliminary investigation demonstrated that PTA1 take part in signal transduction of T cell activation and differentiation as well as platelet activation and aggregation, and PTA1 is also involved in autoimmune diseases, tumors and virus infection. PTA1 cDNA has been cloned from Jurkat cells in 1997 and was shown that it is a novel member of the immunoglobulin superfamily(IgSF) with a 232 aa extracellular region, 25 aa transmembrane region and 61 cytoplasmic region. Identity of PTA1 between activated T cell and platelet was established by the comparison of amino acid sequence deduced from PTA1 cDNA and internal peptide sequences obtained from purified platelet glycoprotein. Recently ,The PTA1 homologous cDNA of ape and monkey was cloned successfully in our Lab, Homology analysis showed that PTA1 molecule is highly conserved among human, ape and monkey, indicated that this molecule may play an important role in immune system. In addition, The PTA1/Ig fusion protein was reconstructed in our Lab and PTA1 ligand may exist on Colo205 tumor cell surface.Here we investigated the expression and localization of PTA1 molecule on human megakaryoblastcyte cell line(HEL) and resting or activated platelets by...