AN ACIDIC COMPONENT OF THE HETEROGENEOUS TC-85 PROTEIN FAMILY FROM THE SURFACE OF TRYPANOSOMA-CRUZI IS A LAMININ-BINDING GLYCOPROTEIN

Successful infection of mammalian host by trypomastigotes of Trypanoso ma cruzi is a complex event, involving host receptors and parasite lig ands. Interaction of the trypomastigote stage with laminin, a componen t of specialized extracellular matrices, as basement membranes, is stu died in this report. Binding of I-125-laminin to trypomastigotes is sp ecific and 2-5 x 10(3) laminin binding sites were calculated to be pre sent on the surface of live trypomastigotes. Antilaminin antibodies we re able to inhibit the invasion of cultured cells by trypomastigotes ( 75-62%), suggesting that laminin may be involved in the adhesion of th e parasite to host cells. By affinity chromatography, an 85-kDa glycop rotein was isolated (laminin binding glycoprotein, LBG) from trypomast igote lysates, but not from epimastigote lysates. It is suggested that at least fragment E8 (but not E1') from laminin could be involved in the reaction which is independent of the carbohydrate moieties from bo th ligand and receptor, as suggested by glycosidase or tunicamycin tre atments. It is also shown that LBG is an acidic component of the polym orphic Tc-85 protein family, a trypomastigote-specific surface membran e glycoprotein which contains several polypeptides recognized by the m onoclonal antibody H1A10, and previously related with the invasion pro cess of the parasite.