Subcellular localization of the delayed rectifier K⁺channels KCNQ1 and ERG1 in the rat heart

Abstract

In the heart, several K+ channels are responsible for the repolarization of the cardiac action potential, including transient outward and delayed rectifier K+ currents. In the present study, the cellular and subcellular localization of the two delayed rectifier K+ channels, KCNQ1 and ether- a- go- go-related gene-1 (ERG1), was investigated in the adult rat heart. Confocal immunofluorescence microscopy of atrial and ventricular cells revealed that whereas KCNQ1 labeling was detected in both the peripheral sarcolemma and a structure transversing the myocytes, ERG1 immunoreactivity was confined to the latter. Immunoelectron microscopy of atrial and ventricular myocytes showed that the ERG1 channel was primarily expressed in the transverse tubular system and its entrance, whereas KCNQ1 was detected in both the peripheral sarcolemma and in the T tubules. Thus, whereas ERG1 displays a very restricted subcellular localization pattern, KCNQ1 is more widely distributed within the cardiac cells. The localization of these K+ channels to the transverse tubular system close to the Ca2+ channels renders them with maximal repolarizing effect.

Kv11.1 (ERG1) K+Channels Localize in Cholesterol and Sphingolipid Enriched Membranes and Are Modulated by Membrane Cholesterol

“…Previous reports have shown expression of Kv11.1 protein in both surface and T-tubular sarcolemma, 36 or predominantly in the T-tubular sarcolemma. 36,37 To examine further surface and T-tubular membrane localization, we performed membrane fractionation to evaluate Kv11.1 immunoreactivity in surface sarcolemma-enriched fractions (FI), T-tubule-enriched fractions (FII), junctional complex-enriched fractions (FIII) and the tissue homogenate (H). 12 The Kv11.1 antibody detected a single protein band of approximately 165 kDa consistent with the complexly-glycosylated mature canine Kv11.1 (cERG1a) in all three fractions with more intense staining in the surface and T-tubular sarcolemmal fractions (Fig.…”

Interstitial Cajal‐like cells (ICLC) in atrial myocardium: ultrastructural and immunohistochemical characterization

“…Table I presents [based on refs. [35][36][37][38][39][40][41][42][43][44][45][46][47] an incomplete survey of literature incidentally documenting (but ignoring) the occurence of ICLC or cell processes/fragments, in atrial myocardium. According to actual criteria for ultrastructural diagnosis [9,13,33], such cells can now be classified as putative ICLC.…”

In vivo monitoring of the potassium channel KcsA in Streptomyces lividans hyphae using immuno-electron microscopy and energy-filtering transmission electron microscopy

“…The bacterial cell wall is not permeable for antibodies, which is why membrane-located KcsA could only be labelled by post-embedding. IEM (using anti-peptide antibodies) was also applied to the KCNQ4 K + channel within the basal membrane of the hair cells of the mouse cochlea (Kharkovets et al, 2000) and the K + channels KCNQ1 and ERG1 within heart cells of rats (Rasmussen et al, 2004). Permeabilized human glioma cells allowed antibodies to access a chloride channel by pre-embedding (Olsen et al, 2003).…”