title: Evidence for the interaction of endophilin a3 with endogenous Kca2.3 channels in PC12 cells.
abstract: OBJECTIVE
  Small-conductance calcium-activated (SK) channels play an important role by controlling the after-hyperpolarization of excitable cells. The level of expression and density of these channels is an essential factor for controlling different cellular functions. Several studies showed a co-localization of K(Ca)2.3 channels and Endophilin A3 in different tissues. Endophilin A3 belongs to a family of BAR- and SH3 domain containing proteins that bind to dynamin and are involved in the process of vesicle scission in clathrin-mediated endocytosis.
  
  
  METHODS
  Using the yeast two-hybrid system and the GST pull down assay we demonstrated that Endophilin A3 interacts with the N-terminal part of K(Ca)2.3 channels. In addition, we studied the impact of this interaction on channel activity by patch clamp measurements in PC12 cells expressing endogenous K(Ca)2.3 channels. K(Ca)2.3 currents were activated by using pipette solutions containing 1 µM free Ca(2+).
  
  
  RESULTS
  Whole-cell measurements of PC12 cells transfected with Endophilin A3 showed a reduction of KCa2.3 specific Cs(+) currents indicating that the interaction of Endophilin A3 with K(Ca)2.3 channels also occurs in mammalian cells and that this interaction has functional consequences for current flowing through K(Ca)2.3 channels. Since K(Ca)2.3 specific currents could be increased in PC12 cells transfected with Endophilin A3 with DC-EBIO (30 µM), a known SK-channel activator, these data also implicate that Endophilin A3 did not significantly remove K(Ca)2.3 channels from the membrane but changed the sensitivity of the channels to Ca(2+) which could be overcome by DC-EBIO.
  
  
  CONCLUSIONS
  This interaction seems to be important for the function of K(Ca)2.3 channels and might therefore play a significant role in situations where channel activation is pivotal for cellular function.
authors.affiliation: Institute of Applied Physiology, University of Ulm, Ulm, Germany.
authors.forename: Malika
authors.initials: M
authors.lastname: Janbein
authors.forename: Mohamed Abo
authors.initials: MA
authors.lastname: Quader
authors.forename: Anselm Cornelius
authors.initials: AC
authors.lastname: Hoppner
authors.forename: Isabell
authors.initials: I
authors.lastname: Grüner
authors.forename: Erich
authors.initials: E
authors.lastname: Wanker
authors.forename: Stephanie
authors.initials: S
authors.lastname: Wälter
authors.forename: Eva
authors.initials: E
authors.lastname: Küppers
authors.forename: Stephan
authors.initials: S
authors.lastname: Grissmer
authors.forename: Heike
authors.initials: H
authors.lastname: Jäger
mesh_terms: D000217:Acyltransferases / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D008969:Molecular Sequence Data; D016716:PC12 Cells; D016133:Polymerase Chain Reaction; D015221:Potassium Channels / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D017386:Sequence Homology, Amino Acid; D020798:Two-Hybrid System Techniques
chemical_list: D017931:DNA Primers; D015221:Potassium Channels; D000217:Acyltransferases; C018764:2-acylglycerophosphate acyltransferase