Inhibition of Kv1.3 potassium current by phosphoinositides and stromal-derived factor-1α in Jurkat T cells

Abstract

The activation of Kv1.3 potassium channel has obligatory roles in immune responses of T lymphocytes. Stromal cell-derived factor-1alpha (SDF-1alpha) binds to C-X-C chemokine receptor type 4, activates phosphoinositide 3-kinase, and plays essential roles in cell migration of T lymphocytes. In this study, the effects of phosphoinositides and SDF-1alpha on Kv1.3 current activity were examined in the Jurkat T cell line using whole cell patch-clamp techniques. The internal application of 10 microM phosphatidylinositol 4,5-bisphosphate (PIP(2)) or 10 microM phosphatidylinositol-3,4,5-trisphosphate (PIP(3)) significantly reduced Kv1.3 current, but that of 10 microM phosphatidylinositol-4-monophosphate (PIP) did not. The coapplication of 10 microg/ml anti-PIP(3) antibody with PIP(2) from the pipette did not change the reduction of Kv1.3 current by PIP(2), but the coapplication of the antibody with PIP(3) eliminated the reduction. The heat-inactivated anti-PIP(3) antibody had no effect on PIP(3)-induced inhibition. These results suggest that PIP(2) per se can reduce Kv1.3 current as well as PIP(3). External application of 1 muM Akt-kinase inhibitor VIII did not reverse the effect of intracellular PIP(3). External application of 10 and 30 ng/ml SDF-1alpha significantly reduced Kv1.3 current. Internal application of anti-PIP(3) antibody reversed the SDF-1alpha-induced reduction. These results suggest that, in Jurkat T cells, PIP(2), PIP(3), and SDF-1alpha reduce Kv1.3 channel activity and that the reduction by SDF-1alpha may be mediated by the enhancement of PIP(3) production. These novel inhibitory effects of phosphoinositides and SDF-1alpha on Kv1.3 current may have a significant function as a downregulation mechanism of Kv1.3 activity for the maintenance of T lymphocyte activation in immune responses.

Peripherally induced human regulatory T cells uncouple Kv1.3 activation from TCR‐associated signaling

“…The association between the Src‐family tyrosine kinase Lck and Kv1.3 is necessary for the initiation of the TCR‐mediated signaling triggered during the formation of the immune synapse 6–8 and has been reported in other, non‐TCR‐dependent, T‐cell responses as well 9–11. Therefore, we explored whether a differential Lck activation in iTregs may concur with the loss of control of Kv1.3 activity by TCR.…”

“…We next wanted to address the question of whether the relocalization and clustering of Lck to the IL‐2‐R complex in iTregs encompassed the regulatory switch of Kv1.3 activity. The functional incidence of Kv1.3 spatial redistribution has been already documented in T cells 6–11. In order to examine whether the TCR‐dissociated Kv1.3 becomes functionally linked to the highly active IL‐2‐R complex, we performed high‐throughput patch clamp analysis with sorted iTregs incubated with IL‐2, IL‐6 or IL‐10.…”

Screening for Acute I Kr Block Is Insufficient to Detect Torsades de Pointes Liability

“…Including PIP3 in the pipette solution in cells exposed to dofetilide for 5 hours reversed AP prolongation (Figure 2D) and inhibited afterdepolarizations; as reported by others, this effect was very rapid. 7,16 Action potentials recorded from control cells with PIP3 in the pipette were no different from action potentials recorded without PIP3 in the pipette. Figure 2E summarizes the frequency of afterdepolarizations in cells studied ≥5 hr after isolation (controls, 0/15), cells exposed to dofetilide for 5 hr after isolation (15/19), and cells exposed to dofetilide for 5 hr after isolation and studied with PIP3 in the pipette (2/15).…”

Dual Regulation of Voltage-Sensitive Ion Channels by PIP2

“…The Kv1.3 channel is important in the activation and function of effector memory T cells (Gilhar et al, 2011 ). Recently, it was reported that PIP 2 applied through patch pipettes in whole-cell recordings significantly reduced Kv1.3 currents in Jurkat T cells and this regulation may be significant for the maintenance of T lymphocyte activation in immune responses (Matsushita et al, 2009 ). However, the mechanisms of this modulation need to be further explored.…”