Immunomodulation of voltage-dependent K+ channels in macrophages: molecular and biophysical consequences

Abstract

Voltage-dependent potassium (Kv) channels play a pivotal role in the modulation of macrophage physiology. Macrophages are professional antigen-presenting cells and produce inflammatory and immunoactive substances that modulate the immune response. Blockage of Kv channels by specific antagonists decreases macrophage cytokine production and inhibits proliferation. Numerous pharmacological agents exert their effects on specific target cells by modifying the activity of their plasma membrane ion channels. Investigation of the mechanisms involved in the regulation of potassium ion conduction is, therefore, essential to the understanding of potassium channel functions in the immune response to infection and inflammation. Here, we demonstrate that the biophysical properties of voltage-dependent K+ currents are modified upon activation or immunosuppression in macrophages. This regulation is in accordance with changes in the molecular characteristics of the heterotetrameric Kv1.3/Kv1.5 channels, which generate the main Kv in macrophages. An increase in K+ current amplitude in lipopolysaccharide-activated macrophages is characterized by a faster C-type inactivation, a greater percentage of cumulative inactivation, and a more effective margatoxin (MgTx) inhibition than control cells. These biophysical parameters are related to an increase in Kv1.3 subunits in the Kv1.3/Kv1.5 hybrid channel. In contrast, dexamethasone decreased the C-type inactivation, the cumulative inactivation, and the sensitivity to MgTx concomitantly with a decrease in Kv1.3 expression. Neither of these treatments apparently altered the expression of Kv1.5. Our results demonstrate that the immunomodulation of macrophages triggers molecular and biophysical consequences in Kv1.3/Kv1.5 hybrid channels by altering the subunit stoichiometry.

Immunomodulatory effects of diclofenac in leukocytes through the targeting of Kv1.3 voltage-dependent potassium channels

“…Although both Kv1.3 and Kv1.5 are present in macrophages, Kv1.3 is the main 15 isoform responsible for cell activation [8,9]. [8,9].…”

“…LightCycler FastStart DNA MasterPLUS SYBR Green I (Roche) was used, and the reactions were performed under the following conditions: 95ºC for 5 s, 55ºC for 8 s, and 72ºC for 9 s, preceded by 7 10 min at 95ºC and followed by 10 min at 95ºC. Melting curves were performed to verify the specificity of the product, and primers for 18S were included as an internal reference [8,9].…”

“…Because the association between Kv1.3 and Kv1.5 generates the major voltagedependent K + current in macrophages [7,9], we wanted to check whether this diclofenac-dependent current decrease was due to changes in the expression of either of these Kv channels. Real-time PCR analysis and, as shown in Fig.…”

“…Kv1.3-high T EM are abundant in these patients, and selective blockage of Kv1.3 ameliorates arthritis in rats [6]. In addition, Kv1.3, together with Kv1.5, is also present in macrophages, where it controls proliferation and activation processes [2,[7][8][9]. Macrophages turn the immune response toward inflammation or tolerance.…”

Ion channels and anti-cancer immunity

“…Monocytes and microglia (resident macrophages in the central nervous system) express voltage-gated Kv1.3 and Ca 2þ -activated KCa3.1 K þ channels, similar to T lymphocytes. In addition, Kv1.5 is also expressed in variable extent in both macrophages and microglia [38,39], and Kv1.3/Kv1.5 heterotetrameric channels are important determinants of the plasma membrane K þ conductance in macrophages [40]. The K þ channels, similar to T cells, regulate the membrane potential of macrophages and microglia, and thus the Ca 2þ influx pathway trough CRAC channels.…”