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Activation of Protein Kinase D1 in Mast Cells in Response to Innate, Adaptive, and Growth Factor Signals¹

Department of Medicine, Harvard Medical School, and Division of Rheumatology, Immunology and Allergy, Brigham and Women’s Hospital, Boston, MA 02115

Little is known about the serine/threonine kinase protein kinase D (PKD)1 in mast cells. We sought to define ligands that activate PKD1 in mast cells and to begin to address the contributions of this enzyme to mast cell activation induced by diverse agonists. Mouse bone marrow-derived mast cells (BMMC) contained both PKD1 mRNA and immunoreactive PKD1 protein. Activation of BMMC through TLR2, Kit, or FcRI with Pam₃CSK₄ (palmitoyl-3-cysteine-serine-lysine-4), stem cell factor (SCF), and cross-linked IgE, respectively, induced activation of PKD1, as determined by immunochemical detection of autophosphorylation. Activation of PKD1 was inhibited by the combined PKD1 and protein kinase C (PKC) inhibitor Gö 6976 but not by broad-spectrum PKC inhibitors, including bisindolylmaleimide (Bim) I. Pam₃CSK₄ and SCF also induced phosphorylation of heat shock protein 27, a known substrate of PKD1, which was also inhibited by Gö 6976 but not Bim I in BMMC. This pattern also extended to activation-induced increases in mRNA encoding the chemokine CCL2 (MCP-1) and release of the protein. In contrast, both pharmacologic agents inhibited exocytosis of β-hexosaminidase induced by SCF or cross-linked IgE. Our findings establish that stimuli representing innate, adaptive, and growth factor pathways activate PKD1 in mast cells. In contrast with certain other cell types, activation of PKD1 in BMMC is largely independent of PKC activation. Furthermore, our findings also indicate that PKD1 preferentially influences transcription-dependent production of CCL2, whereas PKC predominantly regulates the rapid exocytosis of preformed secretory granule mediators.

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.

¹ This work is supported by Grants AI07306, AI41144, and HL36110 from the National Institutes of Health.

² Address correspondence and reprint requests to Dr. Howard R. Katz, Division of Rheumatology, Immunology, and Allergy, Room 638A Brigham and Women’s Hospital, 1 Jimmy Fund Way, Boston, MA 02115. E-mail address: hkatz{at}rics.bwh.harvard.edu

³ Abbreviations used in this paper: PKC, protein kinase C; PKD, protein kinase D; Bim, bisindolylmaleimide; BMMC, bone marrow-derived mast cell; hsp, heat shock protein; MAR, mouse anti-rat IgG; SCF, stem cell factor; WCM, WEHI-3 conditioned medium.