Neurotrophin B receptor kinase increases Kv subfamily member 1.3 (Kv1.3) ion channel half-life and surface expression

• Published in: Neuroscience Vol. 144; no. 2; pp. 531 - 546
• Main Authors: Colley, B.S, Biju, K.C, Visegrady, A, Campbell, S, Fadool, D.A
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 19.01.2007; Elsevier
• Subjects: Biological and medical sciences; Blotting, Western - methods; Brain-Derived Neurotrophic Factor - pharmacology; Cell Line, Transformed; Dose-Response Relationship, Radiation; Electric Stimulation - methods; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation - drug effects; Gene Expression Regulation - physiology; Half-Life; Humans; Immunohistochemistry - methods; Immunoprecipitation - methods; Insulin - pharmacology; Kv1.3 Potassium Channel - genetics; Kv1.3 Potassium Channel - metabolism; Membrane Potentials - physiology; Membrane Potentials - radiation effects; Neurology; neurotrophins; olfactory bulb; Olfactory system and olfaction. Gustatory system and gustation; Patch-Clamp Techniques - methods; potassium channel; Receptor, trkB - metabolism; Shaker; Time Factors; trafficking; Transfection; tyrosine kinase; Vertebrates: nervous system and sense organs; EPL; IPL; N terminus; deactivation time constant; τ Deact; phosphate-buffered saline; P20; BSA; K channel+TrkB kinase; minimum essential medium; Myc; V c; NP40 PPI; wildtype; cDNA; Kv1.5; brain-derived neurotrophic factor; τ Inact; Kv1.3; trafficking; neurotrophin B receptor kinase; V h; PBS; SDS; K channel+dead TrkB kinase; IR; ER; granule cell layer of the olfactory bulb; SDS-PAGE; command voltage; MEM; HEK 293; holding voltage; external plexiform layer of the olfactory bulb; tyrosine; bovine serum albumin; Kv subfamily member 1.3 alone; PCR; protease and phosphatase inhibitor; rt; room temperature; human embryonic kidney 293 cells; Shaker; sodium dodecyl sulfate polyacrylamide gel electrophoresis; F; tyrosine kinase; AU13; PPI; inactivation time constant; K; internal plexiform layer of the olfactory bulb; phosphotyrosine antiserum; anti-PY; GFP; phosphate-buffered saline+Tween; homogenization buffer; insulin receptor kinase; amino terminus of a protein; OB; postnatal day 20; carboxyl terminus of a protein; KD; sodium dodecyl sulfate; Y; antiserum directed against Kv subfamily member 1.3 ion channel; neurotrophins; WT; polymerase chain reaction; olfactory bulb; phenylalanine; BDNF; GL; mitral cell layer of the olfactory bulb; glomerular layer of the olfactory bulb; KT; green florescence protein; GCL; C terminus; TrkB; copy DNA; Kv subfamily member 1.5; Kv subfamily member 1.3; PBST; MCL; myc epitope tag; nonidet-NP40 protease and phosphatase inhibitor; potassium channel; HB; endoplasmic reticulum; Vc; Vh; τInact; τDeact; Neurotrophin; Enzyme; Transferases; Central nervous system; Ionic channel; Encephalon; Olfactory pathway; Kinase; Olfactory bulb; Potassium; Protein-tyrosine kinase; Biological receptor
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2006.09.055

Abstract Kv subfamily member 1.3 (Kv1.3), a member of the Shaker family of potassium channels, has been found to play diverse roles in immunity, metabolism, insulin resistance, sensory discrimination, and axonal targeting in addition to its traditional role in the stabilization of the resting potential. We demonstrate that the neurotrophin B receptor (TrkB) causes an upregulation of Kv1.3 ion channel protein expression in the absence of the preferred ligand for the receptor (brain-derived neurotrophic factor; BDNF) and oppositely downregulates levels of Kv subfamily member 1.5. Although the effect occurs in the absence of the ligand, Kv1.3 upregulation by TrkB is dependent upon the catalytic domain of the TrkB kinase as well as tyrosine (Y) residues in the N and C terminus of the Kv1.3 channel. Using pulse-chase experiments we find that TrkB alters the half-life residence of the channel by approximately 2× and allows it to sustain activity as reflected in an increased current magnitude without alteration of kinetic properties. TrkB and Kv1.3 co-immunoprecipitate from tissue preparations of the mouse olfactory bulb and olfactory cortex, and by immunocytochemical approaches, are found to be co-localized in the glomerular, mitral cell, and internal plexiform layers of the olfactory bulb. These data suggest that Kv1.3 is not only modulated by direct phosphorylation in the presence of BDNF-activated TrkB kinase, but also may be fine tuned via regulation of surface expression while in the proximity of neurotrophic factor receptors. Given the variability of TrkB expression during development, regeneration, or neuronal activation, modulation of surface expression and turnover of Kv channels could significantly impact neuronal excitability, distinct from that of tyrosine kinase phosphorylation.