Role of Kir4.1 channels in growth control of glia
Version of Record online: 17 SEP 2007
Copyright © 2007 Wiley-Liss, Inc.
Volume 55, Issue 16, pages 1668–1679, December 2007
How to Cite
Higashimori, H. and Sontheimer, H. (2007), Role of Kir4.1 channels in growth control of glia. Glia, 55: 1668–1679. doi: 10.1002/glia.20574
- Issue online: 27 SEP 2007
- Version of Record online: 17 SEP 2007
- Manuscript Accepted: 30 JUL 2007
- Manuscript Revised: 24 JUL 2007
- Manuscript Received: 7 JUN 2007
- NIH. Grant Number: RO1 NS31234
- potassium channel;
- resting membrane potential;
- glioma cells
The inwardly rectifying potassium channel Kir4.1 is widely expressed by astrocytes throughout the brain. Kir4.1 channels are absent in immature, proliferating glial cells. The progressive expression of Kir4.1 correlates with astrocyte differentiation and is characterized by the establishment of a negative membrane potential (> −70 mV) and an exit from the cell cycle. Despite some correlative evidence, a mechanistic interdependence between Kir4.1 expression, membrane hyperpolarization, and control of cell proliferation has not been demonstrated. To address this question, we used astrocyte-derived tumors (glioma) that lack functional Kir4.1 channels, and generated two glioma cell lines that stably express either AcGFP-tagged Kir4.1 channels or AcGFP vectors only. Kir4.1 expression confers the same K+ conductance to glioma membranes and a similar responsiveness to changes in [K+]o that characterizes differentiated astrocytes. Kir4.1 expression was sufficient to move the resting potential of gliomas from −50 to −80 mV. Importantly, Kir4.1 expression impaired cell growth by shifting a significant number of cells from the G2/M phase into the quiescent G0/G1 stage of the cell cycle. Furthermore, these effects could be nullified entirely if Kir4.1 channels were either pharmacologically inhibited by 100 μM BaCl2 or if cells were chronically depolarized by 20 mM KCl to the membrane voltage of growth competent glioma cells. These studies therefore demonstrate directly that Kir4.1 causes a membrane hyperpolarization that is sufficient to account for the growth attenuation, which in turn induces cell maturation characterized by a shift of the cells from G2/M into G0/G1. © 2007 Wiley-Liss, Inc.