C-terminus of Human BKca Channel Alpha Subunit Enhances the Permeability of the Brain Endothelial Cells by Interacting with Caveolin-1 and Triggering Caveolin-1 Intracellular Trafficking
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The blood–tumor barrier (BTB) significantly limits the delivery of chemotherapeutic drugs to brain tumors. In this study, we found a significant increase in the permeability of BTB by mediating the association of the C-terminus of alpha subunit of human large-conductance calcium-activated potassium channels (hSlo1c) with caveolin-1 (Cav-1). We present evidence for the first time that hSlo1c associates with Cav-1 in human brain microvascular endothelial cells (HBMECs). A 57-amino acid (966–1022) fragment in hSlo1c was identified to be critical for hSlo1c/Cav-1 interaction. Activation of HBMECs transfected with fusion plasmids of pCMV–hSlo1c containing aa966–1022 by NS1619 selectively enhanced BTB permeability in a BTB model from the co-culture of HBMECs and U87 MG cells but not if the fusion plasmid lacks this fragment. This effect was attenuated by filipin, an agent disrupting caveolae or deletion of the potential interaction fragment, suggesting hSlo1c/Cav-1 association is crucial for regulating the permeability of BTB. Furthermore, we found that hSlo1c/Cav-1 association boosted Cav-1 transferring from the cell membrane to the cytoplasm of HBMECs. Our study indicates that cytoplasmic hSlo1c not only associates with Cav-1 but also has functional consequences on the permeability of BTB by triggering the intracellular trafficking of its interacting protein partner, Cav-1.
KeywordsBKca HSlo1 Caveolin-1 Blood–tumor barrier HBMECs
This work is supported by Grants from the Natural Science Foundation of China (81001029, 81171131, 81172197, 81272564, 81272795, 81100893), the special fund for Scientific Research of Doctor-degree Subjects in Colleges and Universities, (20102104110009), the Natural Science Foundation of Liaoning Province in China (No. 201102300), Liaoning Science and Technology Plan Projects (No. 2011225020), and Shenyang Science and Technology Plan Projects (Nos. F11-264-1-15 and F12-277-1-05).
Conflict of interest
The authors declare no conflict of interest.
- Brainard, A. M., Miller, A. J., Martens, J. R., & England, S. K. (2005). Maxi-K channels localize to caveolae in human myometrium: a role for an actin-channel-caveolin complex in the regulation of myometrial smooth muscle K+ current. American Journal of Physiology-Cell Physiology, 289, C49–C57.PubMedCrossRefGoogle Scholar
- Meera, P., Wallner, M., Song, M., & Toro, L. (1997). Large conductance voltage- and calcium-dependent K+ channel, a distinct member of voltage-dependent ion channels with seven N-terminal transmembrane segments (S0–S6), an extracellular N terminus, and an intracellular (S9–S10) C terminus. Proceedings of the National Academy of Sciences of the United States of America, 94, 14066–14071.PubMedCentralPubMedCrossRefGoogle Scholar
- Proescholdt, M. A., Heiss, J. D., Walbridge, S., Mühlhauser, J., Capogrossi, M. C., Oldfield, E. H., et al. (1999). Vascular endothelial growth factor (VEGF) modulates vascular permeability and inflammation in rat brain. Journal of Neuropathology and Experimental Neurology, 58, 613–627.PubMedCrossRefGoogle Scholar
- Sheikov, N., McDannold, N., Jolesz, F., Zhang, Y. Z., Tam, K., & Hynynen, K. (2006). Brain arterioles show more active vesicular transport of blood-borne tracer molecules than capillaries and venules after focused ultrasound-evoked opening of the blood–brain barrier. Ultrasound in Medicine and Biology, 32, 1399–1409.PubMedCrossRefGoogle Scholar
- Wallner, M., Meera, P., & Toro, L. (1996). Determinant for beta-subunit regulation in high-conductance voltage-activated and Ca2+-sensitive K+ channels: an additional transmembrane region at the N terminus. Proceedings of the National Academy of Sciences of the United States of America, 93, 14922–14927.PubMedCentralPubMedCrossRefGoogle Scholar
- Weksler, B. B., et al. (2005). Blood–brain barrier-specific properties of a human adult brain endothelial cell line. The FASEB Journal, 19, 1872–1874.Google Scholar
- Xie, H., Xue, Y. X., Liu, L. B., Liu, Y. H., & Wang, P. (2012). Role of RhoA/ROCK signaling in endothelial-monocyte-activating polypeptide II opening of the blood–tumor barrier: Role of RhoA/ROCK signaling in EMAP II opening of the BTB. Journal of Molecular Neuroscience, 46, 666–676.PubMedCrossRefGoogle Scholar
- Yuan, F., Chen, Y., Dellian, M., Safabakhsh, N., Ferrara, N., & Jain, R. K. (1996). Time-dependent vascular regression and permeability changes in established human tumor xenografts induced by an anti-vascular endothelial growth factor/vascular permeability factor antibody. Proceedings of the National Academy of Sciences of the United States of America, 93, 14765–14770.PubMedCentralPubMedCrossRefGoogle Scholar