Activation of resting human T cells requires prolonged stimulation of protein kinase C.

Abstract

Purified resting human T cells can be induced to express the a subunit of the interleukin 2 receptor and to proliferate by treatment with 12-O-tetradecanoylphorbol-13-acetate plus ionomycin but not with 1,2-dioctanoylglycerol plus ionomycin. Determination of the translocation of protein kinase C showed that 12-0-tetradecanoylphorbol-13-acetate plus ionomycin caused a prolonged membrane association of the enzyme for more than 4 hr, whereas 1,2-dioctanoylglycerol plus ionomycin induced a transient membrane association, which was maximal at 20 min. Delivery of multiple additions of 1,2-dioctanoylglycerol plus ionomycin to the T cells resulted in progressively increased expression of the a subunit of the interleukin 2 receptor and proliferation commensurate with the number of multiple additions delivered, suggesting that prolonged protein kinase C activity is required for T-cell activation.In several cell types, activation of cell responses results from the receptor-mediated hydrolysis of inositol phospholipids, generating two second messengers, diacylglycerol (DAG) and inositol 1,4,5-trisphosphate, which activate protein kinase C (PKC) and elevate the intracellular Ca2+ concentration, respectively (reviewed in refs. 1 and 2). Antigenic activation of resting human T cells can be mimicked by the synergistic action of the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), which activates PKC, and the calcium ionophore, ionomycin, which raises the intracellular Ca2+ concentration (3). This treatment results in the secretion of interleukin 2 (IL-2) and expression of a 55-kDa a subunit, which combines with a constitutively expressed 70-kDa ,B subunit (4, 5) to form the high-affinity IL-2 receptor (IL-2R; reviewed in ref. 6). Both expression of the a subunit of IL-2R (IL-2Ra) and secretion of IL-2 are controlled at the level of gene transcription (7) and represent a state of irreversible activation ofT cells, because autocrine binding of IL-2 to its cell surface receptor triggers proliferation (8).It was recently demonstrated that, in a >991% pure population of resting human T cells, replacing TPA with membrane-permeable DAGs, which activate PKC in a more physiological manner than TPA, does not induce expression ofthe IL-2Ra or cell proliferation (9). One explanation for the difference in cell response to TPA or DAGs is that TPA stimulates prolonged (longer than 1 hr) activation of PKC (10), whereas DAGs are rapidly converted to the corresponding phosphatidic acid by DAG kinase (11). In the present study, the duration of PKC activation by TPA or by the DAG 1,2-dioctanoylglycerol (DiC8) Chemical (Osaka), trypsin treated with L-1-tosylamido-2-phenylethyl chloromethyl ketone was purchased from Worthington, and soybean trypsin inhibitor was from Sigma. MBP4_14 (GlnLys-Arg-Pro-Ser-Gln-Arg-Ser-Lys-Tyr-Leu), synthesized in this laboratory, is a PKC-specific substrate (A.K. and Y.N., unpublished observations).Preparation of Pure T Lymphocytes. A population of resting T cells was purified from human peripheral ...

Protein kinase C translocation in intact vascular smooth muscle strips

“…2-4, 6 and 7). Although this value is higher than that reported in some studies in isolated cells [2,3,24,25], it is similar to that described in a number of other studies [26][27][28][29] (Fig. 2).…”

Sustained activation of protein kinase C is essential to HL-60 cell differentiation to macrophage.

“…PMA has been shown indeed to cause irreversible insertion of PKC into the membrane, and there appear to be several states of the active form of PKC, although the precise mechanism of this lipid-PKC interaction remains largely unknown (18). With natural signals and also with membranepermeant DAG, however, irreversible association of PKC to membranes was not normally detectable, although some loosely bound, digitonin-nonreleasable form of PKC was produced transiently (10). It is worth noting that, under the conditions in which HL-60 cells undergo terminal differentiation, complete depletion of the a-subspecies of PKC was never observed as described above.…”

Early-response gene signalling is induced by angiogenic oligosaccharides of hyaluronan in endothelial cells. Inhibition by non-angiogenic, high-molecular-weight hyaluronan

“…However, these observations are entirely consistent with studies in other in vitro cell-line models of induced proliferation. For example, chronic exposure of T cells to the protein-kinase-C agonist, phorbol ester, is required to elicit a proliferative response (Berry et al, 1992). Clearly, additional mechanisms, presumably acting in concert with immediate early signalling pathways, underlie the proliferative responses of these cells.…”