期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2014
卷号：111
期号：6
页码：2361-2366
DOI：10.1073/pnas.1317527111
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Ion channels composed of pore-forming and auxiliary subunits control physiological functions in virtually all cell types. A conventional view is that channels assemble with their auxiliary subunits before anterograde plasma membrane trafficking of the protein complex. Whether the multisubunit composition of surface channels is fixed following protein synthesis or flexible and open to acute and, potentially, rapid modulation to control activity and cellular excitability is unclear. Arterial smooth muscle cells (myocytes) express large-conductance Ca2+-activated potassium (BK) channel and auxiliary {beta}1 subunits that are functionally significant modulators of arterial contractility. Here, we show that native BK subunits are primarily ([~]95%) plasma membrane-localized in human and rat arterial myocytes. In contrast, only a small fraction ([~]10%) of total {beta}1 subunits are located at the cell surface. Immunofluorescence resonance energy transfer microscopy demonstrated that intracellular {beta}1 subunits are stored within Rab11A-postive recycling endosomes. Nitric oxide (NO), acting via cGMP-dependent protein kinase, and cAMP-dependent pathways stimulated rapid ([≤]1 min) anterograde trafficking of {beta}1 subunit-containing recycling endosomes, which increased surface {beta}1 almost threefold. These {beta}1 subunits associated with surface-resident BK proteins, elevating channel Ca2+ sensitivity and activity. Our data also show that rapid {beta}1 subunit anterograde trafficking is the primary mechanism by which NO activates myocyte BK channels and induces vasodilation. In summary, we show that rapid {beta}1 subunit surface trafficking controls functional BK channel activity in arterial myocytes and vascular contractility. Conceivably, regulated auxiliary subunit trafficking may control ion channel activity in a wide variety of cell types.
