The focal adhesion protein Testin modulates KCNE2 potassium channel β subunit activity

Abstract

Coronary Artery Disease (CAD) typically kills more people globally each year than any other single cause of death. A better understanding of genetic predisposition to CAD and the underlying mechanisms will help to identify those most at risk and contribute to improved therapeutic approaches. KCNE2 is a functionally versatile, ubiquitously expressed potassium channel β subunit associated with CAD and cardiac arrhythmia susceptibility in humans and mice. Here, to identify novel KCNE2 interaction partners, we employed yeast two-hybrid screening of adult and fetal human heart libraries using the KCNE2 intracellular C-terminal domain as bait. Testin (encoded by TES ), an endothelial cell-expressed, CAD-associated, focal adhesion protein, was identified as a high-confidence interaction partner for KCNE2. We confirmed physical association between KCNE2 and Testin in vitro by co-immunoprecipitation. Whole-cell patch clamp electrophysiology revealed that KCNE2 negative-shifts the voltage dependence and increases the rate of activation of the endothelial cell and cardiomyocyte-expressed Kv channel α subunit, Kv1.5 in CHO cells, whereas Testin did not alter Kv1.5 function. However, Testin nullified KCNE2 effects on Kv1.5 voltage dependence and gating kinetics. In contrast, Testin did not prevent KCNE2 regulation of KCNQ1 gating. The data identify a novel role for Testin as a tertiary ion channel regulatory protein. Future studies will address the potential role for KCNE2-Testin interactions in arterial and myocyte physiology and CAD.

Transcriptional profiling of the developing rat ovary following intrauterine exposure to the endocrine disruptors diethylstilbestrol and ketoconazole

“…Expression pattern P2 included Kcne2 , Dhcr7 and Akr1b7 that were all upregulated in several exposure groups (several doses and developmental stages). Kcne2 encodes an ion transmembrane transport and voltage-gated potassium channel protein (Kundu et al 2008 ) involved in cardiac arrhythmia (Abbott 2012 ; Papanikolaou et al 2021 ). While its role during gonad development is not clearly established, several potassium channels are known to participate in the regulation of progesterone secretion (Kim et al 2020 ).…”

Fluorescence Fluctuation Spectroscopy enables quantification of potassium channel subunit dynamics and stoichiometry

“…We speculate that other cell-to-cell variability in endogenous factors known to affect KCNQ1 and KCNE surface expression and interaction might explain this cell-specific behavior. Possible examples include Protein Kinase C activity, which regulates KCNQ1-KCNE surface expression and interaction 67 – 70 or differential endogenous expression of proteins that interact with KCNE2, such as the focal adhesion protein Testin 71 . Other regulatory influences for diffusion of Kv channels include the underlying cytoskeletal structure, and interactions with other membrane proteins.…”

“…We recorded currents expressed in CHO cell as before 71 using whole-cell patch-clamp at room temperature (22–25 °C) with 3–6 MΩ borosilicate glass electrodes backfilled with solution containing (in mM): 90 K Acetate, 20 KCl, 40 HEPES, 3 MgCl 2 , 1 CaCl 2 , 3 EGTA-KOH, 2 MgATP; pH7.2. We perfused cells continuously at 1–2 ml/min with an extracellular solution containing (in mM): 135 NaCl, 5 KCl, 5 HEPES, 1.2 MgCl 2 , 2.5 CaCl 2 , 10 glucose; pH 7.4.…”

Kv Channel Ancillary Subunits: Where Do We Go from Here?

“…Other classes of protein that serve other functional roles in their own right form in some cases reciprocally regulating complexes with Kv channels, e.g., sodium-coupled solute transporters (79)(80)(81). Finally, ancillary subunits may coordinate coassembly of tertiary regulators into Kv channel complexes (82) or modify the way in which other secondary regulators interact with the Kv a-subunits (70).…”

“…KCNQ1 also forms complexes with KCNE3, 4, and 5, discussed in more detail below (32). Kv1 a-subunits are regulated by Kvb subunits (38,100,101) and also by KCNEs (21,82,(102)(103)(104)(105)(106)(107)(108); Kv2 subunits are regulated by KCNEs (54,55,109); and Kv4 subunits form complexes with KCNEs, KChIPs, and DPP subunits (110)(111)(112)(113)(114). The main classes of Kv a-ancillary interactions are summarized in Table 1.…”