title: Interactions between β-catenin and the HSlo potassium channel regulates HSlo surface expression.
abstract: BACKGROUND
  The large conductance calcium-activated potassium channel alpha-subunit (Slo) is widely distributed throughout the body and plays an important role in a number of diseases. Prior work has shown that Slo, through its S10 region, interacts with β-catenin, a key component of the cytoskeleton framework and the Wnt signaling pathway. However, the physiological significance of this interaction was not clear.
  
  
  RESULTS
  Using a combination of proteomic and cell biology tools we show the existence of additional multiple binding sites in Slo, and explore in detail β-catenin interactions with the S10 region. We demonstrate that deletion of this region reduces Slo surface expression in HEK cells, which indicates that interaction with beta-catenin is important for Slo surface expression. This is confirmed by reduced expression of Slo in HEK cells and chicken (Gallus gallus domesticus leghorn white) hair cells treated with siRNA to β-catenin. HSlo reciprocally co-immunoprecipitates with β-catenin, indicating a stable binding between these two proteins, with the S10 deletion mutant having reduced binding with β-catenin. We also observed that mutations of the two putative GSK phosphorylation sites within the S10 region affect both the surface expression of Slo and the channel's voltage and calcium sensitivities. Interestingly, expression of exogenous Slo in HEK cells inhibits β-catenin-dependent canonical Wnt signaling.
  
  
  CONCLUSIONS
  These studies identify for the first time a central role for β-catenin in mediating Slo surface expression. Additionally we show that Slo overexpression can lead to downregulation of Wnt signaling.
authors.affiliation: Department of Neurology, Yale University School of Medicine, New Haven, Connecticut, United States of America.
authors.forename: Shumin
authors.initials: S
authors.lastname: Bian
authors.forename: Jun-Ping
authors.initials: JP
authors.lastname: Bai
authors.forename: Hannah
authors.initials: H
authors.lastname: Chapin
authors.forename: Cathy
authors.initials: C
authors.lastname: Le Moellic
authors.forename: Huiping
authors.initials: H
authors.lastname: Dong
authors.forename: Michael
authors.initials: M
authors.lastname: Caplan
authors.forename: Fred J
authors.initials: FJ
authors.lastname: Sigworth
authors.forename: Dhasakumar S
authors.initials: DS
authors.lastname: Navaratnam
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D001681:Biological Assay; D002462:Cell Membrane / Q000378:metabolism*; D002645:Chickens; D055785:Gene Knockdown Techniques; D057809:HEK293 Cells; D006198:Hair Cells, Auditory / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D007365:Intercellular Junctions / Q000378:metabolism; D007700:Kinetics; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D010766:Phosphorylation; D011485:Protein Binding; D021381:Protein Transport; D034741:RNA, Small Interfering / Q000378:metabolism; D017384:Sequence Deletion; D014162:Transfection; D060449:Wnt Signaling Pathway; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D050505:Mutant Proteins; D034741:RNA, Small Interfering; D051176:beta Catenin