Regulation of the voltage-gated K⁺ channel KCNA10 by KCNA4B, a novel β-subunit

Abstract

Voltage-gated K+ (Kv) channels are heteromultimeric complexes consisting of pore-forming alpha-subunits and accessory beta-subunits. Several beta-subunits have been identified and shown to interact with specific alpha-subunits to modify their levels of expression or some of their kinetic properties. The aim of the present study was to isolate accessory proteins for KCNA10, a novel Kv channel alpha-subunit functionally related to Kv and cyclic nucleotide-gated cation channels. Because one distinguishing feature of KCNA10 is a putative cyclic nucleotide-binding domain located at the COOH terminus, the entire COOH-terminal region was used to probe a human cardiac cDNA library using the yeast two-hybrid system. Interacting clones were then rescreened in a functional assay by coinjection with KCNA10 in Xenopus oocytes. One of these clones (KCNA4B), when injected alone in oocytes, produced no detectable current. However, when coinjected with KCNA10, it increased KCNA10 current expression by nearly threefold. In addition, the current became more sensitive to activation by cAMP. KCNA4B can be coimmunoprecipitated with the COOH terminus of KCNA10 and full-length KCNA10. It encodes a soluble protein (141 aa) with no amino acid homology to known beta-subunits but with limited structural similarity to the NAD(P)H-dependent oxidoreductase superfamily. KCNA4B is located on chromosome 13 and spans approximately16 kb, and its coding region is made up of five exons. In conclusion, KCNA4B represents the first member of a new class of accessory proteins that modify the properties of Kv channels.

Renalase is a novel, soluble monoamine oxidase that regulates cardiac function and blood pressure

“…Northern blot analysis. Studies were carried out with the entire coding region of the clones of interest as previously described (22).…”

Molecular Diversity and Regulation of Renal Potassium Channels

“…E: the single transmembrane subunit MinK (KCNE1). (552). KCNA4B binds to the carboxy terminus of KCNA10, increases KCNA10 current expression by almost threefold, and also alters its sensitivity to cAMP.…”

“…Two PKC sites are located in the putative cyclic nucleotide-binding domain, suggesting that cyclic nucleotides might modulate the effect of PKC on channel current. A small soluble protein of 141 amino acids, KCNA4B, with limited structural similarity to the NAD(P)H-dependent oxidoreductase superfamily is a ␤-subunit of KCNA10 (552). K ϩ current increases nearly threefold when KCNA4B is coinjected with KCNA10 and becomes more sensitive to activation by cAMP.…”

Possible tetramerisation of the proteasome maturation factor POMP/proteassemblin/hUmp1 and its subcellular localisation

“…The following POMP sequence representing the full length mRNA was used for cloning: GenBank accession number AF262975 (Homo sapiens voltage-gated potassium channel ␤ subunit 4.1, K + v ␤4.1/KCNA4B [23]), which is identical within the coding sequence to AF077200 (HSPC014), that was described as proteassemblin [9], as well as to AF125097 (HSPC036), that was described as hUmp1 [8] and POMP [10]. The cDNA was cloned into the pGEX-4T-3 bacterial expression vector (Amersham Biosciences, Freiburg, Germany) using the following primers for PCR amplification: TG-104 (BamHI): 5 -GCG GGA TCC CGG ATG AAT GCC AGA GGA CTT GGA-3 and TG-105 (XhoI): 5 -CCG CTC GAG CCT ATT ACA GTA AAC CAA GTT TAT ATT CCA CCA T-3 .…”