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The Journal of Neuroscience, July 15, 2000, 20(14):5245-5253
Modulation of Kv1.5 Currents by Src Tyrosine Phosphorylation:
Potential Role in the Differentiation of Astrocytes
Stacey Nee
MacFarlane and
Harald
Sontheimer
Department of Neurobiology, University of Alabama, Birmingham,
Birmingham, Alabama 35294-0021
Using biophysical techniques, we previously have implicated
outwardly rectifying potassium currents in the proliferation of cultured spinal cord astrocytes and have demonstrated that delayed rectifier potassium currents (IKd),
in particular, are upregulated on entry into the cell cycle and
downregulated with cell cycle exit and differentiation. In the present
study, using specific antibodies and antisense oligodeoxynucleotides,
we show that this proliferation-dependent potassium current is mediated
by the Shaker potassium channel Kv1.5. Downregulation of
Kv1.5 protein by antisense oligodeoxynucleotides reduces astrocyte
proliferation by ~50%, although no observed changes occur in Kv1.5
protein expression during spontaneous differentiation in culture.
Tyrosine phosphorylation of Kv1.5, however, is downregulated markedly
in differentiated cells but unaltered on cell cycle arrest. Using
immunoprecipitation, we show that Kv1.5 is associated with Src family
protein tyrosine kinases and that this association does not change with
cell differentiation. Inhibition of kinase activity with the
Src-specific inhibitor PP2 decreases Kv1.5 phosphorylation, reduces
IKd, and inhibits astrocyte
proliferation, specifically in the G0/G1
phase of cell cycle. Conversely, IKd are
potentiated when active Src is present in the pipette. Transfection of
quiescent astrocytes with constitutively active Src (Src Y529F) causes
marked upregulation of astrocyte proliferation. These data suggest that
Kv1.5 is phosphorylated constitutively by Src kinases during growth and
that downregulation of Src activity may underlie both astrocyte
differentiation and the accompanying changes in delayed rectifier
potassium channel activity.
Key words:
Src; proliferation; transfection; PP2; potassium
channels; delayed rectifier
Copyright © 2000 Society for Neuroscience 0270-6474/00/20145245-09$05.00/0
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