ABSTRACT
Exogenously expressed unphosphorylated sub-domains of the R domain block CFTR Cl- channels in the planar lipid bilayer, though the block differs from block with full length R domain. Full length R domain peptide (aa 588-855) blocks CFTR Cl- channels quickly, completely and permanently. Two sub-domains, RD1RD2 (aa 588-805) and RD2TM (aa 672-855), also inhibit CFTR Cl- channels, but the block takes longer to effect and is not complete. Shorter sequences, RD1 (aa 588-746) and RD2 (aa 672-805), fail to effect any block. These data suggest that either the amino-terminal or carboxy-terminal portions of the R domain protein or its stabilized secondary structure are critical to functional regulation.
Subject(s)
Cystic Fibrosis Transmembrane Conductance Regulator/physiology , Cell Line , Cystic Fibrosis Transmembrane Conductance Regulator/genetics , Electrophysiology , Gene Expression , HumansABSTRACT
The cystic fibrosis transmembrane conductance regulator (CFTR) constitutes a linear conductance chloride channel, which is regulated by cAMP-dependent protein kinase phosphorylation at multiple sites located in the intracellular regulatory (R) domain. Studies in a lipid bilayer system, reported here, provide evidence for the control of CFTR chloride channel by its R domain. The exogenous R domain protein (encoded by exon 13 plus 85 base pairs of exon 14) interacted specifically with the CFTR molecule and inhibited the chloride conductance in a phosphorylation-dependent manner. Only the unphosphorylated R domain protein blocked the CFTR channel. Such functional interaction suggests that the putative gating particle of the CFTR chloride channel resides in the R domain.
