Modulation of DRAK2 Autophosphorylation by Antigen Receptor Signaling in Primary Lymphocytes

• Published in: The Journal of biological chemistry Vol. 282; no. 7; pp. 4573 - 4584
• Main Authors: Friedrich, Monica L., Cui, Meng, Hernandez, Jeniffer B., Weist, Brian M., Andersen, Hilde-Marie, Zhang, Xiaowu, Huang, Lan, Walsh, Craig M.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 16.02.2007; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Apoptosis Regulatory Proteins; Calcium Signaling - physiology; Enzyme Activation - physiology; Humans; Jurkat Cells; Lymphocyte Activation - physiology; Mice; Mice, Knockout; Phosphorylation; Protein Processing, Post-Translational - physiology; Protein-Serine-Threonine Kinases - genetics; Protein-Serine-Threonine Kinases - immunology; Protein-Serine-Threonine Kinases - metabolism; Receptors, Antigen, T-Cell - immunology; Receptors, Antigen, T-Cell - metabolism; T-Lymphocytes - enzymology; T-Lymphocytes - immunology
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M606675200

Death-associated protein-related apoptotic kinase-2 (DRAK2), a member of the death-associated protein-like family of serine/threonine kinases, is highly expressed in lymphoid organs and is a negative regulator of T cell activation. To investigate the regulation of DRAK2 activity in primary lymphocytes, we employed mass spectrometry to identify sites of autophosphorylation on DRAK2. These studies have revealed a key site of autophosphorylation on serine 12. Using a phospho-specific antibody to detect Ser12 phosphorylation, we found that autophosphorylation is induced by antigen receptor stimulation in T and B cells. In Jurkat T cells, resting B cells and thymocytes, DRAK2 was hypophosphorylated on Ser12 but rapidly phosphorylated with antigen receptor ligation. This increase in phosphorylation was dependent on intracellular calcium mobilization, because BAPTA-AM blocked DRAK2 kinase activity, whereas the SERCA inhibitor thapsigargin promoted Ser12 phosphorylation. Our results show that DRAK2 kinase activity is regulated in a calcium-dependent manner and that Ser12 phosphorylation is necessary for optimal suppression of T cell activation by this kinase, suggesting a potential feedback loop may act to modulate the activity of this kinase following antigen receptor signaling.