Cross-talk with Ca2+ Influx Does Not Underlie the Role of Extracellular Signal-regulated Kinases in Cytotoxic T Lymphocyte Lytic Granule Exocytosis*
- Department of Physiology and Biophysics, University of Colorado Health Sciences Center, Denver, Colorado 80262
- ‡ To whom correspondence should be addressed: Dept. of Physiology and Biophysics, University of Colorado Health Sciences Center, 4200 E. 9th Ave., Denver, CO 80262. Tel.: 303-315-5007; Fax: 303-315-8110; E-mail: adam.zweifach{at}UCHSC.edu.
Abstract
One important mechanism cytotoxic T lymphocytes use to kill target cells is exocytosis of lytic granules that contain cytotoxic agents such as perforin and granzyme. Ca2+ influx and activation of protein kinase C have been known for many years to be key signals for granule exocytosis. Recent work has suggested that activation of extracellular signal-regulated kinases (ERK), members of the mitogen-activated protein kinase (MAP kinase) family, may be a third required signal. We surmised that the involvement of ERK in lytic granule exocytosis could be mediated through cross-talk with Ca2+ influx, rather than constituting an independent signal. We tested this idea using TALL-104 human leukemic CTLs as a model system and discovered the following. 1) ERK inhibition caused a modest decrease in the amplitude of increases in intracellular Ca2+ concentration, but this effect cannot account for the profound inhibition of granule exocytosis. 2) Ca2+ influx can activate ERK in TALL-104 cells, but this effect does not contribute to ERK activation stimulated by solid phase anti-CD3 monoclonal antibodies. We conclude that cross-talk between ERK signaling and Ca2+ does not mediate the role of ERK in CTL lytic granule exocytosis.
Footnotes
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↵1 The abbreviations used are: CTL, cytotoxic T lymphocyte; TCR, T cell receptor; [Ca2+]i, intracellular Ca2+ concentration; Ca2+o, extracellular Ca2+; PKC, protein kinase C; ERK, extracellular signal-regulated kinase; MAP kinase, mitogen-activated protein kinase; CCE, capacitative calcium entry; MTOC, microtubule-organizing center; PMA, phorbol myristate acetate; mAb, monoclonal antibody; CHAPS, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid; 7-AAD, 7-amino-actinomycin D; TG, thapsigargin; BLT, Nα-benzyloxycarbonyl-l-lysine thiobenzyl ester; MEK, mitogen-activated protein kinase/extracellular signal-regulated kinase kinase; NK, natural killer cells.
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↵2 A. Zweifach and G. A. Wurth, unpublished observations.
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↵* This work was supported by National Institutes of Health Grant AI054839. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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- Received January 12, 2004.
- Revision received March 18, 2004.
- The American Society for Biochemistry and Molecular Biology, Inc.
