Deglycosylation of the beta1-subunit of the BK channel changes its biophysical properties

Am J Physiol Cell Physiol. 2006 Oct;291(4):C750-6. doi: 10.1152/ajpcell.00116.2006. Epub 2006 May 31.

Abstract

Large-conductance Ca(2+)-activated potassium (BK) channels are composed of pore-forming alpha-subunits and auxiliary beta-subunits. The alpha-subunits are widely expressed in many cell types, whereas the beta-subunits are more tissue specific and influence diverse aspects of channel function. In the current study, we identified the presence of the smooth muscle-specific beta1-subunit in murine colonic tissue using Western blotting. The native beta1-subunits migrated in SDS-PAGE as two molecular mass bands. Enzymatic removal of N-linked glycosylations from the beta1-subunit resulted in a single band that migrated at a lower molecular mass than the native beta1-subunit bands, suggesting that the native beta1-subunit exists in either a core glycosylated or highly glycosylated form. We investigated the functional consequence of deglycosylating the beta1-subunit during inside-out single-channel recordings. During inside-out single-channel recordings, with N-glycosidase F in the pipette solution, the open probability (P(o)) and mean open time of BK channels increased in a time-dependent manner. Deglycosylation of BK channels did not affect the conductance but shifted the steady-state voltage of activation toward more positive potentials without affecting slope when Ca(2+) concentration was <1 microM. Treatment of myocytes lacking the beta1-subunits of the BK channel with N-glycosidase F had no effect. These data suggest that glycosylations on the beta1-subunit in smooth muscle cells can modify the biophysical properties of BK channels.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Biophysical Phenomena
  • Biophysics
  • Cations, Divalent / pharmacology
  • Colon / cytology
  • Colon / metabolism*
  • Electric Conductivity
  • Glycosylation* / drug effects
  • Homeostasis / drug effects
  • Large-Conductance Calcium-Activated Potassium Channels / deficiency
  • Large-Conductance Calcium-Activated Potassium Channels / drug effects
  • Large-Conductance Calcium-Activated Potassium Channels / metabolism
  • Large-Conductance Calcium-Activated Potassium Channels / physiology*
  • Mice
  • Mice, Inbred BALB C
  • Mice, Knockout
  • Myocytes, Smooth Muscle / metabolism*
  • Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase / pharmacology
  • Protein Isoforms / deficiency
  • Protein Isoforms / drug effects
  • Protein Isoforms / metabolism
  • Protein Isoforms / physiology

Substances

  • Cations, Divalent
  • Large-Conductance Calcium-Activated Potassium Channels
  • Protein Isoforms
  • Peptide-N4-(N-acetyl-beta-glucosaminyl) Asparagine Amidase