Alternatively spliced C-terminal domains regulate the surface expression of large conductance calcium-activated potassium channels

• Published in: Neuroscience 2007-06, Vol.146 (4), p.1652-1661
• Main Authors: Kim, E.Y, Ridgway, L.D, Zou, S, Chiu, Y.-H, Dryer, S.E
• Format: Article
• Language: English
• Subjects: Alternative Splicing - physiology; Analysis of Variance; Animals; Biological and medical sciences; Biotinylation - methods; Cells, Cultured; Chick Embryo; ciliary ganglion; Fundamental and applied biological sciences. Psychology; Ganglia, Parasympathetic - cytology; Gene Expression Regulation - genetics; Gene Expression Regulation - physiology; Green Fluorescent Proteins - genetics; Green Fluorescent Proteins - metabolism; Humans; Large-Conductance Calcium-Activated Potassium Channels - genetics; Large-Conductance Calcium-Activated Potassium Channels - metabolism; Membrane Potentials - genetics; Mice; neuregulin; Neurology; Neurons - metabolism; PDZ; Peripheral nervous system. Autonomic nervous system. Neuromuscular transmission. Ganglionic transmission. Electric organ; Protein Structure, Tertiary; Protein Transport - physiology; Rats; Reverse Transcriptase Polymerase Chain Reaction - methods; RNA, Messenger - biosynthesis; Slo1; traffic; Transfection - methods; Vertebrates: nervous system and sense organs
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2007.03.038

Abstract The Slo1 gene, also known as KCNMA1 , encodes the pore-forming subunits of large-conductance Ca2+ -activated K+ (BKCa ) channels. Products of this gene are widely expressed in vertebrate tissues, and occur in a large number (≥20) of alternatively spliced variants that vary in their gating properties, susceptibility to modulation, and trafficking to the plasma membrane. Motifs in the large cytoplasmic C-terminal are especially important in determining the functional properties of BKCa channels. Here we report that chick ciliary ganglion neurons express transcripts and proteins of two Slo1 splice variants that differ at the extreme C-terminal. We refer to these variants as VEDEC and QEDRL (or QEERL for the orthologous mammalian versions), after the five terminal amino acid residues in each isoform. Individual ciliary ganglion neurons preferentially express these variants in different subcellular compartments. Moreover, QEERL channels show markedly higher levels of constitutive expression on the plasma membrane than VEDEC channels in HEK293T and NG108-15 cells. However, growth factor treatment can stimulate surface expression of VEDEC channels to levels comparable to those seen with QEERL. In addition, we show that co-expression of a soluble protein composed of VEDEC C-terminal tail residues markedly increases cell surface expression of full-length VEDEC channels, suggesting that this region binds to proteins that cause retention of the these channels in intracellular stores.