HIV-Tat induces a decrease in I Kr and I Ks via reduction in phosphatidylinositol-(4,5)-bisphosphate availability

Abstract

Patients with HIV present with a higher prevalence of QT prolongation, of which molecular bases are still not clear. Among HIV proteins, Tat serves as a transactivator that stimulates viral genes expression and is required for efficient HIV replication. Tat is actively secreted into the blood by infected T-cells and affects organs such as the heart. Tat has been shown to alter cardiac repolarization in animal models but how this is mediated and whether this is also the case in human cells is unknown. In the present study, we show that Tat transfection in heterologous expression systems led to a decrease in hERG (underlying cardiac I Kr ) and human KCNE1-KCNQ1 (underlying cardiac I Ks ) currents and to an acceleration of their deactivation. This is consistent with a decrease in available phosphatidylinositol-(4,5)-bisphosphate (PIP 2 ). A mutant Tat, unable to bind PIP 2 , did not reproduce the observed effects. In addition, WT-Tat had no effect on a mutant KCNQ1 which is PIP 2 -insensitive, further confirming the hypothesis. Twenty four-hour incubation of human induced pluripotent stem cells-derived cardiomyocytes with Wild-type Tat reduced I Kr and accelerated its deactivation. Concordantly, this Tat incubation led to a prolongation of the action potential (AP) duration. Events of AP alternans were also recorded in the presence of Tat, and were exacerbated at a low pacing cycle length. Altogether, these data obtained on human K + channels both in heterologous expression systems and in human cardiomyocytes strongly suggest that Tat sequesters PIP 2 , leading to a reduction of I Kr and I Ks , and provide a molecular mechanism for QT prolongation in HIV-infected patients.

hERG S4-S5 linker acts as a voltage-dependent ligand that binds to the activation gate and locks it in a closed state

“…Bound antibodies were detected using horseradish peroxidase-conjugated rabbit anti-goat (Santa Cruz Biotechnology, ref: SC-2922), goat anti-rabbit (Santa Cruz Biotechnology, ref: SC-2054), and goat anti-mouse (Santa Cruz Biotechnology, ref: SC-2055) secondary antibodies. Stain free gel technology (Bio-Rad) was used as loading control for protein normalization: band intensities were first normalized to the intensity of the corresponding stain free membrane lane, and ratios were then normalized to control hERG condition 35 .…”

A computational model of induced pluripotent stem‐cell derived cardiomyocytes incorporating experimental variability from multiple data sources

“…Dataset-specific models of steady-state activation were fit to four independent iPSC-CM experimental datasets from the Wu Lab (Garg et al 2018), as well as from Ma et al (2011), Bellin et al (2013) and Es-Salah-Lamoureux et al (2016). The data by Es-Salah-Lamoureux et al 2016were collected from an in-house iPSC-CM line and the data by Bellin et al (2013) were collected from a patient-specific cell line.…”

“…Voltage-dependent time constants of activation were extracted from current recordings published in Ma et al (2011). The time constants of activation in Ma et al (2011) were used to optimize parameters in the optimized models of Ma et al (2011), the Wu Lab (Garg et al 2018) and Es-Salah-Lamoureux et al (2016). Experimental time constants of activation were published in Bellin et al (2013) and used in the corresponding model, as shown in green in Fig.…”

“…13D-F represent a single model in the given population. Additionally, these outputs are compared w2ith experimentally measured iPSC-CM outputs shown as black dots and lines (Ma et al 2011;Doss et al 2012;Cordeiro et al 2013;Ma et al 2015;Es-Salah-Lamoureux et al 2016;Herron et al 2016), as was performed for the baseline model in Fig. 11.…”

Regulation of KCNQ/Kv7 family voltage-gated K + channels by lipids

“…For example, extracellular osmolarity dependent changes in intracellular Mg 2+ or polyamine concentration modulate the channel-PIP 2 interaction and consequently I Ks current [134]. In another example, HIV-tat mediated PIP 2 sequestration reduces both I Ks and I Kr leading to QT prolongation in the HIV-infected population [135]. Similarly, mutations in Kv7.1 or KCNE1 that lead to a reduction in Kv7.1-PIP 2 affinity have been associated with congenital LQTS [114, 136, 137].…”