Dataset Information

ER-associated degradation of Eag1 potassium channels by the RING E3 ubiquitin ligase MKRN1: the presence of a dual ubiquitination system

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 mutant channel is linked to defective protein stability that involves enhanced protein degradation by the E3 ubiquitin ligase cullin 7 (CUL7). The detailed mechanisms governing protein homeostasis of plasma membrane- and endoplasmic reticulum (ER)-localized Eag1 K+ channels, however, remains 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 non-glycosylated, 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, non-glycosylated 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.

INSTRUMENT(S): LCQ Classic

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Chen-Chung Liao

LAB HEAD: Chen-Chung Liao

PROVIDER: PXD023984 | Pride | 2021-09-10

REPOSITORIES: Pride

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Publications

Identification of MKRN1 as a second E3 ligase for Eag1 potassium channels reveals regulation via differential degradation.

Fang Ya-Ching YC Fu Ssu-Ju SJ Hsu Po-Hao PH Chang Pei-Tzu PT Huang Jing-Jia JJ Chiu Yi-Chih YC Liao Yi-Fan YF Jow Guey-Mei GM Tang Chih-Yung CY Jeng Chung-Jiuan CJ

The Journal of biological chemistry 20210101

Mutations in the human gene encoding the neuron-specific Eag1 voltage-gated K<sup>+</sup> 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<sup>+</su ...[more]

PMID: 33647316

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Project description:N-glycosylation is an important posttranslational modification in all eukaryotes, but little is known about the N-glycoproteomes in microalgal systems. Here, N-glycoproteome of the model diatom Phaeodactylum tricornutum was unveiled. Totally, 893 different N-glycosylated sites from 649 proteins were identified from P. tricornutum. The new synthesized N-glycans were principally transferred to asparagine residues within the conserved N-X-S/T (where X is a residue other than proline) sequence of nascent polypeptide chains. Functional annotation of N-glycosylated proteins showed that 70% N-glycoproteins were involved in vesicular transport and posttranslational modification, protein turnover, chaperones, indicating the N-glycosylation was important for these functions. Of the all identified N-glycoproteins 45.3% were predicted to localize on chloroplast, which implied the widespread regulatory role of N-glycosylation in chloroplast. Furthermore, the enrichment results of N-glycoproteins indicated that compared to ‘Cellular component’ and ‘Biological process’ categories proteins related with the ‘Molecular function’ category were more prone to be N-glycosylated. And it was speculated that N-glycosylation played a vital regulatory role in catalytic activity of enzymes and metabolism processes of many small molecules. 47% of all enriched proteins were related with metabolic pathways. The functional annotation and enrichment of N-glycoproteins suggested that N-glycoproteins participated in a variety of important metabolic pathways and perform different functions in P. tricornutum. 12 proteins involved in the ER quality control mechanism and ER- associated degradation pathway were identified as N-glycosylated proteins, indicating that the N-glycosylated modification was important for their functions in the protein N-glycosylation pathway. Additionally, some interacted glycoproteins were classified from this study, which provided valuable information for studying the functions of these glycoproteins. In the study, the identification of N-glycosylation on nascent proteins expands our understanding of this PTM at a proteomics scale and may facilitate the elucidation of the precise function of proteins in this model diatom.

Dataset Information

ER-associated degradation of Eag1 potassium channels by the RING E3 ubiquitin ligase MKRN1: the presence of a dual ubiquitination system

Publications

Identification of MKRN1 as a second E3 ligase for Eag1 potassium channels reveals regulation via differential degradation.

Similar Datasets

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