Hydrolysis of Phosphatidylinositol 4, 5‐Bisphosphate and Increase in Cytosolic Free Ca²⁺‐Concentration Induced in a Human T Cell Leukemia Line, JURKAT, by Monoclonal Antibodies against the T3 Complex

Abstract

The monoclonal antibodies against the T3 complex on human T lymphocytes, anti-Leu-4, OKT3, and T3, induced an accumulation of inositol phosphates in a human T cell leukemia line, JURKAT, in the presence of LiCl. The monoclonal antibodies also induced an increase in the cytosolic free Ca2+-concentration ([Ca2]i) in JURKAT. The accumulation of inositol phosphates and the increase in [Ca2+]i were specifically induced by the monoclonal antibodies against the T3 complex. Other monoclonal antibodies against differentiation antigens on human T lymphocytes were not active in inducing these responses in JURKAT. Stimulation of JURKAT by anti-Leu-4 induced a rapid and immediate decrease in phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] and an increase in the 32P-labeling of phosphatidic acid, which occurred after a short lag period. An analysis of inositol phosphates formed in the anti-Leu-4-stimulated JURKAT indicated the formation of inositol trisphosphate. These results strongly suggested that the T3 complex or T3/antigen receptor (Ti) complex functions as a receptor which transduces antigen signal, presented by either antigen-presenting cells or target cells, into the hydrolysis of Ptdlns(4,5)P2. Fetal bovine serum at a dose oi ly after addition. However, the level of formation of inositol phosphates was very small in cells stimulated by fetal bovine serum. Fetal bovine serum induced an immediate increase in the 32P-labeling of phosphatidic acid in JURKAT. These and other results suggested that serum increased [Ca2]i in JURKAT by a mechanism different from that for the anti-Leu-4-induced [Ca2]i response.

Activation of polyphosphoinositide phospholipase C by guanosine 5′‐O‐(3‐thio)triphosphate and fluoroaluminate in membranes prepared from a human T cell leukemia line, JURKAT

“…At least one receptor, or possibly the only receptor [4,5], participating in the lectin-induced transmembrane signaling is the T-cell antigen receptor composed of the clonotypic oe/fl chain heterodimer (Ti) and its associated, monomorphic molecules, three CD3 subunits and CD3-~" subunits [6]. Thus, monoclonal antibodies directed against either Ti or CD3 induce the increase in [CaZ+]i and the hydrolysis of Ptdlns(4,5)P2 in JURKAT [4,[7][8][9]. These results indicate that the activation of T lymphocytes by antigen presenting cells and target cells induces the hydrolysis of Ptdlns(4,5)Pz and subsequent increase in [Ca2+]i and activation of protein kinase C.…”

Suppression by staurosporine of Ca2+‐mobilization triggered by ligation of antigen‐specific receptors on T and B lymphocytes An essential role of protein tyrosine kinase in the signal transduction

“…The receptor-stimulated activation of PLC in such ligand-receptor systems as those used in this study [2,4,8,9,11,16,21,22,26,27] can be indirectly monitored by the Ca*'. responses, which are by far more sensitive and convenient than the assay of ['Hlinositol phosphate release from the cells labeled with myot3H]inositol.…”