title: Modulation of Kv1.3 channels by protein kinase A I in T lymphocytes is mediated by the disc large 1-tyrosine kinase Lck complex.
abstract: 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.
authors.affiliation: Department of Internal Medicine, 231 Albert Sabin Way, University of Cincinnati, Cincinnati, OH 45267-0585, USA.
authors.forename: Zerrin
authors.initials: Z
authors.lastname: Kuras
authors.forename: Vladimir
authors.initials: V
authors.lastname: Kucher
authors.forename: Scott M
authors.initials: SM
authors.lastname: Gordon
authors.forename: Lisa
authors.initials: L
authors.lastname: Neumeier
authors.forename: Ameet A
authors.initials: AA
authors.lastname: Chimote
authors.forename: Alexandra H
authors.initials: AH
authors.lastname: Filipovich
authors.forename: Laura
authors.initials: L
authors.lastname: Conforti
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology*; D002478:Cells, Cultured; D054743:Cyclic AMP-Dependent Protein Kinase Type I / Q000502:physiology*; D000074288:Discs Large Homolog 1 Protein; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D019169:Jurkat Cells; D051664:Kv1.3 Potassium Channel / Q000378:metabolism*; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck) / Q000037:antagonists & inhibitors / Q000502:physiology*; D008565:Membrane Proteins / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013601:T-Lymphocytes / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C513314:DLG1 protein, human; D000074288:Discs Large Homolog 1 Protein; D007166:Immunosuppressive Agents; D051664:Kv1.3 Potassium Channel; D008565:Membrane Proteins; D015124:8-Bromo Cyclic Adenosine Monophosphate; D019860:Lymphocyte Specific Protein Tyrosine Kinase p56(lck); D054743:Cyclic AMP-Dependent Protein Kinase Type I