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Protein ubiquitination extensively modulates protein functions and controls various biological processes, such as protein degradation, signal transduction, transcription, and DNA repair. Ubiquitination is a reversible post‐translational modification, and deubiquitinating enzymes cleave ubiquitin from proteins. Ubiquitin‐specific peptidase 46 (USP46), a deubiquitinase, is highly expressed in the brain and regulates neural functions. Deleting lysine 92 (ΔK92) in USP46 reduces murine depression‐like behavior in the tail suspension test. However, the molecular basis for USP46's role in regulating neural function has not yet been fully understood. Here we employed a proximity‐dependent biotinylation approach to characterize the USP46 protein interaction partners. Using homology‐independent targeted integration (HITI), a genome editing technique, we established knockin cell lines that stably express USP46 wildtype‐ or ΔK92‐biotin ligase fusion protein. We identified 286 candidate interaction partners, including well‐known binding partners of USP46. Although there were no obvious differences in the interactome of USP46 between wildtype and ΔK92, a gene ontology analysis revealed that centrosome‐related proteins were significantly enriched in the proximal proteins of USP46. Several centrosome‐related proteins were bound to USP46 in Neuro2a cells, but their protein expression levels were not affected in the brains of USP46‐deficient mice. These results uncover a potential relationship between USP46 and centrosome regulation independently of protein stabilization. [ABSTRACT FROM AUTHOR]

The most common cystic fibrosis mutation, ΔF508 in nucleotide binding domain 1 (NBD1), impairs cystic fibrosis transmembrane conductance regulator (CFTR)-coupled domain folding, plasma membrane expression, function and stability. VX-809, a promising investigational corrector of ΔF508-CFTR misprocessing, has limited clinical benefit and an incompletely understood mechanism, hampering drug development. Given the effect of second-site suppressor mutations, robust ΔF508-CFTR correction most likely requires stabilization of NBD1 energetics and the interface between membrane-spanning domains (MSDs) and NBD1, which are both established primary conformational defects. Here we elucidate the molecular targets of available correctors: class I stabilizes the NBD1-MSD1 and NBD1-MSD2 interfaces, and class II targets NBD2. Only chemical chaperones, surrogates of class III correctors, stabilize human ΔF508-NBD1. Although VX-809 can correct missense mutations primarily destabilizing the NBD1-MSD1/2 interface, functional plasma membrane expression of ΔF508-CFTR also requires compounds that counteract the NBD1 and NBD2 stability defects in cystic fibrosis bronchial epithelial cells and intestinal organoids. Thus, the combination of structure-guided correctors represents an effective approach for cystic fibrosis therapy.

The ubiquitin E3 ligase UBE3C promotes the proteasomal degradation of cytosolic proteins and endoplasmic reticulum (ER) membrane proteins. UBE3C is proposed to function downstream of the RNF185/MBRL ER-associated degradation (ERAD) branch, contributing to the ERAD of select membrane proteins. Here, we report that UBE3C facilitates the ERAD of misfolded CFTR, even in the absence of both RNF185 and its functional ortholog RNF5 (RNF5/185). Unlike RNF5/185, UBE3C had a limited impact on the ubiquitination of misfolded CFTR. UBE3C knockdown (KD) resulted in an additional increase in the functional ∆F508-CFTR channels on the plasma membrane when combined with the RNF5/185 ablation, particularly in the presence of clinically used CFTR modulators. Interestingly, although UBE3C KD failed to attenuate the ERAD of insig-1, it reduced the ERAD of misfolded ∆Y490-ABCB1 and increased cell surface expression. UBE3C KD also stabilized the mature form of ∆F508-CFTR and increased the cell surface level of T70-CFTR, a class VI CFTR mutant. These results suggest that UBE3C plays a vital role in the ERAD of misfolded CFTR and ABCB1, even within the RNF5/185-independent ERAD pathway, and it may also be involved in maintaining the peripheral quality control of CFTR. [ABSTRACT FROM AUTHOR]

This document, titled "J. Cyst. Fibros. 20 (5), 895–898," published in the journal Frontiers in Pharmacology, discusses a study on cystic fibrosis. The study explores the potential benefits of a new pharmacological treatment for cystic fibrosis patients. The authors provide an overview of the disease and its impact on patients, as well as the current treatment options available. The study concludes that the new treatment shows promise in improving lung function and reducing symptoms in cystic fibrosis patients. [Extracted from the article]