Altered outward-rectifying K+ current reveals microglial activation induced by HIV-1 Tat protein

Abstract

Microglial cells are believed to be one of the key elements in the development of the HIV–related neuropathology. Not only can microglial cells be productively infected by the virus, but they are also sensitive to viral proteins. Among them, the HIV‐1 regulatory protein Tat, which was shown to have neurotoxic activity, is able to promote some proinflammatory functions of microglia. Considering that microglial activation goes along with a change of ion channel profile, we aimed to study whether Tat could influence microglial electrophysiology. When microglial cultures obtained from neonatal rats were treated with Tat (≥ 100 ng/ml), whole‐cell recording showed the appearance of a large outwardly rectifying current (OR) virtually absent in untreated control cells. According to voltage dependence of the kinetic variables, K+ permeability, and pharmacological sensitivity, the Tat‐induced current was due to the presence of functional Kv1.3 channels. The effect of Tat was abolished by specific anti‐Tat polyclonal antibody and by heat denaturation of Tat protein, confirming that the OR enhancement was due to the viral protein. Interestingly, the OR current induced by Tat was largely prevented by two inhibitors of the transcription factor NF‐κB, TPCK and SN50, which suggests an involvement of NF‐κB in the effect of the viral protein. The relatively high dose of Tat needed to observe an effect (≥ 100 ng/ml) might indicate that the action of Tat required entrance of the protein into the cell, rather than being mediated by a membrane receptor. In conclusion, the HIV‐1 protein Tat is able to enhance OR K+ current in rat microglia through a mechanism involving the activation of NF‐κB. We propose that such effect of Tat could be part of the process of microglial activation known to take place in the brain of persons with neuro‐AIDS. GLIA 33:181–190, 2001. © 2001 Wiley‐Liss, Inc.

HIV-1 Tat Protein Increases Microglial Outward K+ Current and Resultant Neurotoxic Activity

“…Tat protein has also been shown capable of increasing an outward-rectifying K + current in rat microglia through regulation of transcription factor NF-κB [49]. However, while K v 1.3 channel activity has here been demonstrated to be necessary for Tat-induced microglial neurotoxicity, the underlying connection remains to be elucidated.…”

HIV-1 Tat Protein Increases Microglial Outward K+ Current and Resultant Neurotoxic Activity

“…Tat protein has also been shown capable of increasing an outward-rectifying K + current in rat microglia through regulation of transcription factor NF-κB [49]. However, while K v 1.3 channel activity has here been demonstrated to be necessary for Tat-induced microglial neurotoxicity, the underlying connection remains to be elucidated.…”

Biocompatibility of silicon nanowires: A step towards IC detectors

“…3, a). Likewise, when investigating BV-2 cells in voltage-clamp experiments to test for their membrane expression of voltage-activated IR or OR K + channels [23], we found no difference across seeding conditions (Fig. 3, b).…”

Silicon nanowires to detect electric signals from living cells

“…In particular, in current-clamp experiments we found that in response to the injection of hyperpolarizing and depolarizing current steps NG108CC15 cells had both passive properties (resting membrane potential; membrane capacitance; voltage sag and input resistance; not shown) and active response (firing profile) unaltered by the presence of SiNWs as seeding substrate ( figure 5, a). Likewise, when investigating BV-2 cells in voltageclamp experiments to test for their membrane expression of voltage-activated IR or OR K + channels [45], we found no difference across seeding conditions (figure 5, b; for patch-clamp experiments, n = 3-to-4 cells per condition; p>0.3 or more, unpaired t-test when applicable).…”

HIV-1 Tat Protein Increases Microglial Outward K+ Current and Resultant Neurotoxic Activity

“…Tat protein has also been shown capable of increasing an outward-rectifying K + current in rat microglia through regulation of transcription factor NF-κB [49]. However, while K v 1.3 channel activity has here been demonstrated to be necessary for Tat-induced microglial neurotoxicity, the underlying connection remains to be elucidated.…”

Biocompatibility of silicon nanowires: A step towards IC detectors

“…3, a). Likewise, when investigating BV-2 cells in voltage-clamp experiments to test for their membrane expression of voltage-activated IR or OR K + channels [23], we found no difference across seeding conditions (Fig. 3, b).…”

Silicon nanowires to detect electric signals from living cells

“…In particular, in current-clamp experiments we found that in response to the injection of hyperpolarizing and depolarizing current steps NG108CC15 cells had both passive properties (resting membrane potential; membrane capacitance; voltage sag and input resistance; not shown) and active response (firing profile) unaltered by the presence of SiNWs as seeding substrate ( figure 5, a). Likewise, when investigating BV-2 cells in voltageclamp experiments to test for their membrane expression of voltage-activated IR or OR K + channels [45], we found no difference across seeding conditions (figure 5, b; for patch-clamp experiments, n = 3-to-4 cells per condition; p>0.3 or more, unpaired t-test when applicable).…”

HIV-1 Tat Protein Increases Microglial Outward K+ Current and Resultant Neurotoxic Activity

“…Tat protein has also been shown capable of increasing an outward-rectifying K + current in rat microglia through regulation of transcription factor NF-κB [49]. However, while K v 1.3 channel activity has here been demonstrated to be necessary for Tat-induced microglial neurotoxicity, the underlying connection remains to be elucidated.…”

Biocompatibility of silicon nanowires: A step towards IC detectors

“…3, a). Likewise, when investigating BV-2 cells in voltage-clamp experiments to test for their membrane expression of voltage-activated IR or OR K + channels [23], we found no difference across seeding conditions (Fig. 3, b).…”

Silicon nanowires to detect electric signals from living cells

“…In particular, in current-clamp experiments we found that in response to the injection of hyperpolarizing and depolarizing current steps NG108CC15 cells had both passive properties (resting membrane potential; membrane capacitance; voltage sag and input resistance; not shown) and active response (firing profile) unaltered by the presence of SiNWs as seeding substrate ( figure 5, a). Likewise, when investigating BV-2 cells in voltageclamp experiments to test for their membrane expression of voltage-activated IR or OR K + channels [45], we found no difference across seeding conditions (figure 5, b; for patch-clamp experiments, n = 3-to-4 cells per condition; p>0.3 or more, unpaired t-test when applicable).…”