Modulation of Kv1.3 channels by protein kinase A I in T lymphocytes is mediated by the disc large 1-tyrosine kinase Lck complex

• Published in: American Journal of Physiology: Cell Physiology Vol. 302; no. 10; p. C1504
• Main Authors: Kuras, Zerrin, Kucher, Vladimir, Gordon, Scott M, Neumeier, Lisa, Chimote, Ameet A, Filipovich, Alexandra H, Conforti, Laura
• Format: Journal Article
• Language: English
• Published: United States 15-05-2012
• Subjects: 8-Bromo Cyclic Adenosine Monophosphate - pharmacology; Adaptor Proteins, Signal Transducing - physiology; Cells, Cultured; Cyclic AMP-Dependent Protein Kinase Type I - physiology; Humans; Immunosuppressive Agents - pharmacology; Jurkat Cells; Kv1.3 Potassium Channel - metabolism; Lymphocyte Specific Protein Tyrosine Kinase p56(lck) - antagonists & inhibitors; Lymphocyte Specific Protein Tyrosine Kinase p56(lck) - physiology; Membrane Proteins - physiology; Signal Transduction - drug effects; Signal Transduction - physiology; T-Lymphocytes - drug effects; T-Lymphocytes - enzymology; T-Lymphocytes - metabolism
• ISSN: 1522-1563
• DOI: 10.1152/ajpcell.00263.2011

The cAMP/PKA signaling system constitutes an inhibitory pathway in T cells and, although its biochemistry has been thoroughly investigated, its possible effects on ion channels are still not fully understood. K(V)1.3 channels play an important role in T-cell activation, and their inhibition suppresses T-cell function. It has been reported that PKA modulates K(V)1.3 activity. Two PKA isoforms are expressed in human T cells: PKAI and PKAII. PKAI has been shown to inhibit T-cell activation via suppression of the tyrosine kinase Lck. The aim of this study was to determine the PKA isoform modulating K(V)1.3 and the signaling pathway underneath. 8-Bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP), a nonselective activator of PKA, inhibited K(V)1.3 currents both in primary human T and in Jurkat cells. This inhibition was prevented by the PKA blocker PKI(6-22). Selective knockdown of PKAI, but not PKAII, with siRNAs abolished the response to 8-BrcAMP. Additional studies were performed to determine the signaling pathway mediating PKAI effect on K(V)1.3. Overexpression of a constitutively active mutant of Lck reduced the response of K(V)1.3 to 8-Br-cAMP. Moreover, knockdown of the scaffolding protein disc large 1 (Dlg1), which binds K(V)1.3 to Lck, abolished PKA modulation of K(V)1.3 channels. Immunohistochemistry studies showed that PKAI, but not PKAII, colocalizes with K(V)1.3 and Dlg1 indicating a close proximity between these proteins. These results indicate that PKAI selectively regulates K(V)1.3 channels in human T lymphocytes. This effect is mediated by Lck and Dlg1. We thus propose that the K(V)1.3/Dlg1/Lck complex is part of the membrane pathway that cAMP utilizes to regulate T-cell function.