Modulation of glioma BK channels via erbB2.

Abstract

Glioma cells show up-regulation and constitutive activation of erbB2, and its expression correlates positively with increased malignancy. A similar correlation has been demonstrated for the expression of gBK, a calcium-sensitive, large-conductance K(+) channel. We show here that glioma BK channels are a downstream target of erbB2/neuregulin signaling. Tyrphostin AG825 was able to disrupt the constituitive erbB2 activation in a dose-dependent manner, causing a 30-mV positive shift in gBK channel activation in cell-attached patches. Conversely, maximal stimulation of erbB2 with a recombinant neuregulin (NRG-1beta) caused a 12-mV shift in the opposite direction. RT-PCR studies reveal no change in the BK splice variants expressed in treated glioma cells. Furthermore, isolation of surface proteins through biotinylation did not show a change in gBK channel expression, and probing with phospho-specific antibodies showed no alteration in channel phosphorylation. However, fura-II Ca(2+) fluorescence imaging revealed a 35% decrease in the free intracellular Ca(2+) concentration after erbB2 inhibition and an increase in NRG-1beta-treated cells, suggesting that the observed changes most likely were due to alterations in [Ca(2+)](i). Consistent with this conclusion, neither tyrphostin AG825 nor NRG-1beta was able to modulate gBK channels under inside-out or whole-cell recording conditions when intracellular Ca(2+) was fixed. Thus, gBK channels are a downstream target for the abundantly expressed neuregulin-1 receptor erbB2 in glioma cells. However, unlike the case in other systems, this modulation appears to occur via changes in [Ca(2+)](i) without changes in channel expression or phosphorylation. The enhanced sensitivity of gBK channels in glioma cells to small, physiological Ca(2+) changes appears to be a prerequisite for this modulation.

• Authors: M L Olsen, A K Weaver, P S Ritch, H Sontheimer
• Journal: Journal of neuroscience research (J Neurosci Res) Vol. 81 Issue 2 Pg. 179-89 (Jul 15 2005) ISSN: 0360-4012 [Print] United States
• PMID: 15948146 (Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Benzothiazoles
• Large-Conductance Calcium-Activated Potassium Channels
• Neuregulins
• Potassium Channels, Calcium-Activated
• Tyrphostins
• tyrphostin AG825
• Protein-Tyrosine Kinases
• Receptor, ErbB-2
• Calcium

Topics

• Benzothiazoles
• Brain Neoplasms (metabolism)
• Calcium (metabolism)
• Cell Line, Tumor
• Glioblastoma (metabolism)
• Humans
• Large-Conductance Calcium-Activated Potassium Channels
• Neuregulins (metabolism)
• Potassium Channels, Calcium-Activated (drug effects, metabolism)
• Protein-Tyrosine Kinases (antagonists & inhibitors)
• Receptor, ErbB-2 (drug effects, physiology)
• Signal Transduction (drug effects, physiology)
• Tyrphostins (pharmacology)