Epithelial Na+ channel subunit stoichiometry. Biophys J 2005 Jun;88(6):3966-75
Date
04/12/2005Pubmed ID
15821171Pubmed Central ID
PMC1305628DOI
10.1529/biophysj.104.056804Scopus ID
2-s2.0-22244458247 (requires institutional sign-in at Scopus site) 99 CitationsAbstract
Ion channels, including the epithelial Na(+) channel (ENaC), are intrinsic membrane proteins comprised of component subunits. Proper subunit assembly and stoichiometry are essential for normal physiological function of the channel protein. ENaC comprises three subunits, alpha, beta, and gamma, that have common tertiary structures and much amino acid sequence identity. For maximal ENaC activity, each subunit is required. The subunit stoichiometry of functional ENaC within the membrane remains uncertain. We combined a biophysical approach, fluorescence intensity ratio analysis, used to assess relative subunit stoichiometry with total internal reflection fluorescence microscopy, which enables isolation of plasma membrane fluorescence signals, to determine the limiting subunit stoichiometry of ENaC within the plasma membrane. Our results demonstrate that membrane ENaC contains equal numbers of each type of subunit and that at steady state, subunit stoichiometry is fixed. Moreover, we find that when all three ENaC subunits are coexpressed, heteromeric channel formation is favored over homomeric channels. Electrophysiological results testing effects of ENaC subunit dose on channel activity were consistent with total internal reflection fluorescence/fluorescence intensity ratio findings and confirmed preferential formation of heteromeric channels containing equal numbers of each subunit.
Author List
Staruschenko A, Adams E, Booth RE, Stockand JDMESH terms used to index this publication - Major topics in bold
Amino Acid SequenceAnimals
Biophysical Phenomena
Biophysics
CHO Cells
COS Cells
Cell Membrane
Cricetinae
Epithelial Sodium Channels
Microscopy, Fluorescence
Protein Subunits
Recombinant Fusion Proteins
Sodium Channels
