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Functional Kir7.1 channels localized at the root of apical processes in rat retinal pigment epithelium
Author(s) -
Kusaka Shunji,
Inanobe Atsushi,
Fujita Akikazu,
Makino Yasunaka,
Tanemoto Masayuki,
Matsushita Kenji,
Tano Yasuo,
Kurachi Yoshihisa
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.0027j.x
Subject(s) - retinal pigment epithelium , microbiology and biotechnology , potassium channel , biology , hek 293 cells , epithelium , chemistry , cell culture , retinal , anatomy , biophysics , biochemistry , genetics
1 The inwardly rectifying K + channel current ( I K(IR) ) recorded from isolated retinal pigmented epithelial (RPE) cells showed poor dependence on external K + ([K + ] o ) and low sensitivity to block by Ba 2+ . We examined the molecular identity and specific subcellular localization of the K IR channel in RPE cells. 2 The Kir7.1 channel current heterologously expressed in HEK293T cells (human embryonic kidney cell line) showed identical properties to those of the RPE I K(IR) , i.e. poor dependence on [K + ] o and low sensitivity to Ba 2+ block. 3 Expression of Kir7.1 mRNA and protein was detected in RPE cells by RT‐PCR and immunoblot techniques, respectively. 4 Immunohistochemical studies including electron microscopy revealed that the Kir7.1 channel was localized specifically at the proximal roots of the apical processes of RPE cells, where Na + ,K + ‐ATPase immunoreactivity was also detected. 5 The middle‐distal portions of apical processes of RPE cells in the intact tissue exhibited immunoreactivity of Kir4.1, a common K IR channel. In the isolated RPE cells, however, Kir4.1 immunoreactivity was largely lost, while Kir7.1 immunoreactivity remained. 6 These data indicate that the only I K(IR) recorded in isolated RPE cells is derived from the functional Kir7.1 channel localized at the root of apical processes. Co‐localization with Na + ,K + ‐ATPase suggests that the Kir7.1 channel may provide the pathway for recycling of K + to maintain pump activity and thus is essential for K + handling in RPE cells.