Identification of MKRN1 as a second E3 ligase for Eag1 potassium channels reveals regulation via differential degradation
Journal
Journal of Biological Chemistry
Journal Volume
296
Pages
100484
Date Issued
2021
Author(s)
Fang Y.-C.
Fu S.-J.
Hsu P.-H.
Chang P.-T.
Huang J.-J.
Chiu Y.-C.
Liao Y.-F.
Jow G.-M.
Jeng C.-J.
Abstract
Mutations in the human gene encoding the neuron-specific Eag1 voltage-gated K+ channel are associated with neurodevelopmental diseases, indicating an important role of Eag1 during brain development. A disease-causing Eag1 mutation is linked to decreased protein stability that involves enhanced protein degradation by the E3 ubiquitin ligase cullin 7 (CUL7). The general mechanisms governing protein homeostasis of plasma membrane- and endoplasmic reticulum (ER)-localized Eag1 K+ channels, however, remain unclear. By using yeast two-hybrid screening, we identified another E3 ubiquitin ligase, makorin ring finger protein 1 (MKRN1), as a novel binding partner primarily interacting with the carboxyl-terminal region of Eag1. MKRN1 mainly interacts with ER-localized immature core-glycosylated, as well as nascent nonglycosylated, Eag1 proteins. MKRN1 promotes polyubiquitination and ER-associated proteasomal degradation of immature Eag1 proteins. Although both CUL7 and MKRN1 contribute to ER quality control of immature core-glycosylated Eag1 proteins, MKRN1, but not CUL7, associates with and promotes degradation of nascent, nonglycosylated Eag1 proteins at the ER. In direct contrast to the role of CUL7 in regulating both ER and peripheral quality controls of Eag1, MKRN1 is exclusively responsible for the early stage of Eag1 maturation at the ER. We further demonstrated that both CUL7 and MKRN1 contribute to protein quality control of additional disease-causing Eag1 mutants associated with defective protein homeostasis. Our data suggest that the presence of this dual ubiquitination system differentially maintains Eag1 protein homeostasis and may ensure efficient removal of disease-associated misfolded Eag1 mutant channels. ? 2021 THE AUTHORS.
SDGs
Other Subjects
Cell membranes; Diagnosis; Disease control; Gene encoding; Potassium; Quality assurance; Quality control; Differential degradation; Endoplasmic reticulum; Polyubiquitination; Potassium channels; Proteasomal degradation; Protein degradation; Protein quality control; Protein stability; Proteins; cullin; cullin 7; Eag1 protein; makorin ring finger protein 1; potassium channel; ubiquitin protein ligase E3; unclassified drug; Kcnh1 protein, rat; Makorin ring finger protein 1; nerve protein; potassium channel HERG; ribonucleoprotein; ubiquitin protein ligase; animal cell; animal experiment; Article; carboxy terminal sequence; controlled study; disease association; endoplasmic reticulum; human; human cell; hybridization; nonhuman; priority journal; protein analysis; protein binding; protein degradation; protein function; protein glycosylation; protein homeostasis; protein localization; protein processing; protein protein interaction; protein quality; quality control; rat; ubiquitination; yeast; animal; cell culture; metabolism; nerve cell; protein degradation; Sprague Dawley rat; two hybrid system; ubiquitination; Animals; Cells, Cultured; Endoplasmic Reticulum; Ether-A-Go-Go Potassium Channels; Nerve Tissue Proteins; Neurons; Proteolysis; Proteostasis; Rats; Rats, Sprague-Dawley; Ribonucleoproteins; Two-Hybrid System Techniques; Ubiquitin-Protein Ligases; Ubiquitination
Publisher
American Society for Biochemistry and Molecular Biology Inc.
Type
journal article