Defective human Ether-à-go-go-related gene trafficking linked to an endoplasmic reticulum retention signal in the C terminus.
Mutations in the human Ether-à-go-go-Related gene (HERG), encoding the protein underlying the cardiac K(+) current, I(Kr), cause chromosome 7-linked long QT syndrome (LQT2). In this study, we show that deletion of the C-terminal 147 amino acids (HERG(Delta147)) abolished I(Kr), whereas a larger, 159-amino acid deletion (HERG(Delta159)) identified in an LQT2 kindred did generate I(Kr), albeit with reduced amplitude compared with the wild type. The 12 amino acids present in HERG(Delta147) and absent in HERG(Delta159) include a potential endoplasmic reticulum (ER) retention signal, RGR, which when mutated to LGL (HERG(Delta147-LGL)) restored I(Kr). Streptavidin selection of biotin-labeled surface proteins showed good expression of wild-type and HERG(Delta159) at the cell surface and low expression of HERG(Delta147-LGL) and HERG(Delta147). Additionally, a 100-amino acid peptide spanning the RGR triplet can rescue the defect in HERG(Delta147) when co-expressed as an ER-targeted minigene. Failure of HERG trafficking is known to cause LQT2, and this identified a molecular mechanism underlying this defect. Further, our data indicate that a key function of the C-terminal 104 amino acids is to mask the RGR ER retention signal, which becomes exposed when mutations truncate the HERG C terminus.
Kupershmidt
Sabina
S
Departments of Pharmacology and Medicine, Vanderbilt University School of Medicine, 561A Preston Research Building, Nashville, TN 37232, USA. sabina.kupershmidt@vanderbilt.edu
Yang
Tao
T
Chanthaphaychith
Siprachanh
S
Wang
Zhiqing
Z
Towbin
Jeffrey A
JA
Roden
Dan M
DM
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D019921:Biotinylation; D015153:Blotting, Western; D016466:CHO Cells; D027682:Cation Transport Proteins; D006224:Cricetinae; D004268:DNA-Binding Proteins; D000072237:ERG1 Potassium Channel; D004594:Electrophysiology; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D051638:Ether-A-Go-Go Potassium Channels; D017353:Gene Deletion; D006801:Humans; D008564:Membrane Potentials; D008954:Models, Biological; D008957:Models, Genetic; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D010957:Plasmids / Q000378:metabolism; D015221:Potassium Channels / Q000235:genetics* / Q000378:metabolism*; D024642:Potassium Channels, Voltage-Gated; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG
D027682:Cation Transport Proteins; D004268:DNA-Binding Proteins; C072312:ERG protein, human; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; C092509:KCNH6 protein, human; D010455:Peptides; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG