Modulation of K_V1.3 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.

Selective Inhibition of KCa3.1 Channels Mediates Adenosine Regulation of the Motility of Human T Cells

“…Furthermore, a similar effect was observed with the PKAI inhibitor Rp-8Br-cAMP (100 μM, Fig. 4B) (38). …”

Immunosuppressive evidence of Tityus serrulatus toxins Ts6 and Ts15: insights of a novel K+ channel pattern in T cells

“…Our results are also supported by a previous study, which demonstrated that although Kv1.3 blockers do not prevent immunological synapse formation, they suppress Ca 2+ signalling, cytokine production and proliferation of T EM cells . For a detailed Kv1.3 mechanism of T‐cell functional modulation mediated by Kv1.3/Dgl1/Lck complex, see Kuras et al 2012 …”

Membrane microdomain organization, calcium signal, and NFAT activation as an important axis in polarized Th cell function

“…Furthermore, the cease or altered kinetics of the redistribution of Kv1.3 channels during engagement of T cells in immunological synapse can also modify Ca 2+ ‐responses. In addition, a scaffolding protein of Kv1.3 (Dlgh1/CARMA‐1), which can bind and couple various protein kinases to the channel, such as p56lck and PKA, was demonstrated to promote NFAT activation (54, 57, 58). Based on these, we suppose that the control of Kv1.3 current in Th1 cell lineage may be due to the modification of the channel by protein kinases, rather than targeting to distinct lipid compartments, although it cannot be excluded, either.…”