Membrane trafficking of large conductance calcium-activated potassium channels is regulated by alternative splicing of a transplantable, acidic trafficking motif in the RCK1-RCK2 linker.
Trafficking of the pore-forming alpha-subunits of large conductance calcium- and voltage-activated potassium (BK) channels to the cell surface represents an important regulatory step in controlling BK channel function. Here, we identify multiple trafficking signals within the intracellular RCK1-RCK2 linker of the cytosolic C terminus of the channel that are required for efficient cell surface expression of the channel. In particular, an acidic cluster-like motif was essential for channel exit from the endoplasmic reticulum and subsequent cell surface expression. This motif could be transplanted onto a heterologous nonchannel protein to enhance cell surface expression by accelerating endoplasmic reticulum export. Importantly, we identified a human alternatively spliced BK channel variant, hSloDelta(579-664), in which these trafficking signals are excluded because of in-frame exon skipping. The hSloDelta(579-664) variant is expressed in multiple human tissues and cannot form functional channels at the cell surface even though it retains the putative RCK domains and downstream trafficking signals. Functionally, the hSloDelta(579-664) variant acts as a dominant negative subunit to suppress cell surface expression of BK channels. Thus alternative splicing of the intracellular RCK1-RCK2 linker plays a critical role in determining cell surface expression of BK channels by controlling the inclusion/exclusion of multiple trafficking motifs.
Chen
Lie
L
Centre for Integrative Physiology, College of Medicine & Veterinary Medicine, University of Edinburgh, Edinburgh EH8 9XD, Scotland, United Kingdom.
Jeffries
Owen
O
Rowe
Iain C M
IC
Liang
Zhi
Z
Knaus
Hans-Guenther
HG
Ruth
Peter
P
Shipston
Michael J
MJ
D017398:Alternative Splicing; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D003001:Cloning, Molecular; D005091:Exons / Q000235:genetics; D005786:Gene Expression Regulation; D006801:Humans; D042541:Intracellular Space / Q000378:metabolism; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D020033:Protein Isoforms / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion
D051036:Large-Conductance Calcium-Activated Potassium Channels; D020033:Protein Isoforms