Role of G-proteins in T cell activation: non-hydrolysable GTP analogues induce early ornithine decarboxylase activity in human T lymphocytes.

Abstract

Rapid activation of ornithine decarboxylase is one of the earliest recognized events during induction of a mitogenic response in human T lymphocytes. Here we show that the non‐hydrolysable GTP analogues guanine‐5‐(gamma‐thio)trisphosphate and guanylyl‐5‐imidodiphosphate, introduced into human T cells by means of a transient membrane permeabilization technique, can replace an external mitogenic ligand, such as concanavalin A, in inducing early ornithine decarboxylase activity. Neomycin inhibits this rapid activation at concentrations known to bind to phosphoinositides. One of the two compounds formed in polyphosphoinositide breakdown, inositol‐1,4,5‐trisphosphate, also induces ornithine decarboxylase activity. The other, diacylglycerol, apparently does not, since the phorbol ester, tetradecanoyl phorbol acetate, which is thought to mimic the action of diacylglycerols, does not alter basal ornithine decarboxylase activity in T cells until several hours after administration. These findings indicate that guanine nucleotide‐binding regulatory (G‐) protein(s) participates in the transduction of the mitogenic signal. The intracellular target system for this G‐protein may include phosphoinositide breakdown and generation of inositoltrisphosphate, which might be involved in the early activation of ornithine decarboxylase.

The [Ca2+]i increase induced in murine thymocytes by extracellular ATP does not involve ATP hydrolysis and is not related to phosphoinositide metabolism

“…Our data suggest that such receptors linked to increased calcium influx might mediate the [Ca'+]i rise in thymocytes, maybe by pore formation as suggested by Tathan et al [26] in the case of rat mast cells, which might explain that ATP in the presence of EDTA has been used to permeabilize human T lymphocyte membrane to impermeable compounds [29]. The high ATP concentration (in the range of 100 PM) needed to promote the calcium response might be explained by the presence of ecto-ATPase on the cell membrane [lo], the Ca-ATP complex being a substrate of this enzyme; such concentrations have been reported in other tissues for P2 receptors linked to the activation of the phosphoinositide pathway [4][5][6]8].…”

A role for guanine-nucleotide-binding proteins in mediating T-cell-receptor coupling to inositol phospholipid hydrolysis in a murine T-helper (type II) lymphocyte clone

“…These receptors include those responsible for the response of neutrophils to chemotactic ligands [11,12] or the stimulation of B-lymphocytes triggered via the immunoglobulin receptor [13,14]. With regard to T-lymphocytes, G-proteins have been implicated in the secretory response of cytotoxic T-cells [15], the activation of ornithine decarboxylase in human peripheral-blood T-cells [16], the release of interleukin-2 by Jurkat T-cell leukaemia [17] or a T-cell hybridoma [18], Ca2l mobilization in thymocytes [19] and the activation of InsPL metabolism in a T-cell hybridoma [20], Jurkat cells [17,21], and peripheral-blood lymphocytes [22]. Data are, however, scarce with regard to the role of G-proteins in coupling TCR to an effector function or to InsPL hydrolysis in particular.…”

Interleukin 3‐stimulated proliferation is sensitive to pertussis toxin: Evidence for a guanyl nucleotide regulatory protein‐mediated signal transduction mechanism

“…Cells were permeabilized by the procedure ofMustelin et al (1986). Briefly, cells were washed three times Effect of PT on IL-3-stimulated proliferation; 1 x lo6 76A1 or BG.S/UT cells were cultured with various concentrations of IL-3 and 10% PS with or without 10 ng/ml of PT.…”