Chemical mimetics of the N-degron pathway alleviate systemic inflammation by activating mitophagy and immunometabolic remodeling.

The Arg/N-degron pathway, which is involved in the degradation of proteins bearing an N-terminal signal peptide, is connected to p62/SQSTM1-mediated autophagy. However, the impact of the molecular link between the N-degron and autophagy pathways is largely unknown in the context of systemic inflammation. Here, we show that chemical mimetics of the N-degron Nt-Arg pathway (p62 ligands) decreased mortality in sepsis and inhibited pathological inflammation by activating mitophagy and immunometabolic remodeling. The p62 ligands alleviated systemic inflammation in a mouse model of lipopolysaccharide (LPS)-induced septic shock and in the cecal ligation and puncture model of sepsis. In macrophages, the p62 ligand attenuated the production of proinflammatory cytokines and chemokines in response to various innate immune stimuli. Mechanistically, the p62 ligand augmented LPS-induced mitophagy and inhibited the production of mitochondrial reactive oxygen species in macrophages. The p62 ligand-mediated anti-inflammatory, antioxidative, and mitophagy-activating effects depended on p62. In parallel, the p62 ligand significantly downregulated the LPS-induced upregulation of aerobic glycolysis and lactate production. Together, our findings demonstrate that p62 ligands play a critical role in the regulation of inflammatory responses by orchestrating mitophagy and immunometabolic remodeling.

Chemical modulation of SQSTM1/p62-mediated xenophagy that targets a broad range of pathogenic bacteria.

The N-degron pathway is a proteolytic system in which the N-terminal degrons (N-degrons) of proteins, such as arginine (Nt-Arg), induce the degradation of proteins and subcellular organelles via the ubiquitin-proteasome system (UPS) or macroautophagy/autophagy-lysosome system (hereafter autophagy). Here, we developed the chemical mimics of the N-degron Nt-Arg as a pharmaceutical means to induce targeted degradation of intracellular bacteria via autophagy, such as Salmonella enterica serovar Typhimurium (S. Typhimurium), Escherichia coli, and Streptococcus pyogenes as well as Mycobacterium tuberculosis (Mtb). Upon binding the ZZ domain of the autophagic cargo receptor SQSTM1/p62 (sequestosome 1), these chemicals induced the biogenesis and recruitment of autophagic membranes to intracellular bacteria via SQSTM1, leading to lysosomal degradation. The antimicrobial efficacy was independent of rapamycin-modulated core autophagic pathways and synergistic with the reduced production of inflammatory cytokines. In mice, these drugs exhibited antimicrobial efficacy for S. Typhimurium, Bacillus Calmette-Guérin (BCG), and Mtb as well as multidrug-resistant Mtb and inhibited the production of inflammatory cytokines. This dual mode of action in xenophagy and inflammation significantly protected mice from inflammatory lesions in the lungs and other tissues caused by all the tested bacterial strains. Our results suggest that the N-degron pathway provides a therapeutic target in host-directed therapeutics for a broad range of drug-resistant intracellular pathogens.Abbreviations: ATG: autophagy-related gene; BCG: Bacillus Calmette-Guérin; BMDMs: bone marrow-derived macrophages; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; CFUs: colony-forming units; CXCL: C-X-C motif chemokine ligand; EGFP: enhanced green fluorescent protein; IL1B/IL-1ß: interleukin 1 beta; IL6: interleukin 6; LIR: MAP1LC3/LC3-interacting region; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; Mtb: Mycobacterium tuberculosis; MTOR: mechanistic target of rapamycin kinase; NBR1: NBR1 autophagy cargo receptor; OPTN: optineurin; PB1: Phox and Bem1; SQSTM1/p62: sequestosome 1; S. Typhimurium: Salmonella enterica serovar Typhimurium; TAX1BP1: Tax1 binding protein 1; TNF: tumor necrosis factor; UBA: ubiquitin-associated.

Post-Marketing Pooled Safety Analysis for CT-P13 Treatment of Patients with Immune-Mediated Inflammatory Diseases in Observational Cohort Studies.

BACKGROUND: At EU marketing authorisation, safety data for CT-P13 (biosimilar infliximab) were limited, particularly in some indications, and uncommon adverse events (AEs) could not be evaluated among relatively small analysis populations. OBJECTIVES: Our objective was to investigate the overall safety profile and incidence rate of AEs of special interest (AESIs), including serious infections and tuberculosis, in CT-P13-treated patients. METHODS: Data were pooled from six observational studies representing authorised indications of CT-P13 (ankylosing spondylitis, rheumatoid arthritis, psoriatic arthritis, plaque psoriasis, adult and paediatric Crohn's disease and ulcerative colitis). Patients were analysed by indication and treatment (patients who received CT-P13 or those who switched from reference infliximab to CT-P13 ≤ 6 months prior to enrolment or during the study). RESULTS: Overall, 4393 patients were included (n = 3677 CT-P13 group; n = 716 switched group); 64.03% of patients had inflammatory bowel disease and 6.31% of patients were antidrug antibody positive. Overall, 32.94% and 9.58% of patients experienced treatment-emergent AEs (TEAEs) and treatment-emergent serious AEs, respectively. Across indications, TEAEs were more frequent with CT-P13 than with the switched group. Infections including tuberculosis were the most frequent serious AESI overall (2.48%) and by treatment group or indication. In total, 14 patients (0.32%) reported active tuberculosis. Overall incidence rates per 100 patient-years (95% confidence interval) were 3.40 (2.788-4.096) for serious infections including tuberculosis and 0.44 (0.238-0.732) for active tuberculosis. Infusion-related reactions were the second most frequent AESI following infection including tuberculosis. CONCLUSION: The CT-P13 safety profile appears consistent with previous studies for CT-P13 and reference infliximab, supporting the favourable risk/benefit balance for CT-P13 treatment.

NRF2/ARE pathway negatively regulates BACE1 expression and ameliorates cognitive deficits in mouse Alzheimer's models.

BACE1 is the rate-limiting enzyme for amyloid-ß peptides (Aß) generation, a key event in the pathogenesis of Alzheimer's disease (AD). By an unknown mechanism, levels of BACE1 and a BACE1 mRNA-stabilizing antisense RNA (BACE1-AS) are elevated in the brains of AD patients, implicating that dysregulation of BACE1 expression plays an important role in AD pathogenesis. We found that nuclear factor erythroid-derived 2-related factor 2 (NRF2/NFE2L2) represses the expression of BACE1 and BACE1-AS through binding to antioxidant response elements (AREs) in their promoters of mouse and human. NRF2-mediated inhibition of BACE1 and BACE1-AS expression is independent of redox regulation. NRF2 activation decreases production of BACE1 and BACE1-AS transcripts and Aß production and ameliorates cognitive deficits in animal models of AD. Depletion of NRF2 increases BACE1 and BACE1-AS expression and Aß production and worsens cognitive deficits. Our findings suggest that activation of NRF2 can prevent a key early pathogenic process in AD.

The N-recognin UBR4 of the N-end rule pathway is targeted to and required for the biogenesis of the early endosome.

The N-end rule pathway is a proteolytic system in which single N-terminal residues of proteins act as N-degrons. These degrons are recognized by N-recognins, facilitating substrate degradation via the ubiquitin (Ub) proteasome system (UPS) or autophagy. We have previously identified a set of N-recognins [UBR1, UBR2, UBR4 (also known as p600) and UBR5 (also known as EDD)] that bind N-degrons through their UBR boxes to promote proteolysis by the proteasome. Here, we show that the 570 kDa N-recognin UBR4 is associated with maturing endosomes through an interaction with Ca2+-bound calmodulin. The endosomal recruitment of UBR4 is essential for the biogenesis of early endosomes (EEs) and endosome-related processes, such as the trafficking of endocytosed protein cargos and degradation of extracellular cargos by endosomal hydrolases. In mouse embryos, UBR4 marks and plays a role in the endosome-lysosome pathway that mediates the heterophagic proteolysis of endocytosed maternal proteins into amino acids. By screening 9591 drugs through the DrugBank database, we identify picolinic acid as a putative ligand for UBR4 that inhibits the biogenesis of EEs. Our results suggest that UBR4 is an essential modulator in the endosome-lysosome system.This article has an associated First Person interview with the first author of the paper.

The N-recognin UBR4 of the N-end rule pathway is required for neurogenesis and homeostasis of cell surface proteins.

The N-end rule pathway is a proteolytic system in which single N-terminal amino acids of proteins act as a class of degrons (N-degrons) that determine the half-lives of proteins. We have previously identified a family of mammals N-recognins (termed UBR1, UBR2, UBR4/p600, and UBR5/EDD) whose conserved UBR boxes bind N-degrons to facilitate substrate ubiquitination and proteasomal degradation via the ubiquitin-proteasome system (UPS). Amongst these N-recognins, UBR1 and UBR2 mediate ubiquitination and proteolysis of short-lived regulators and misfolded proteins. Here, we characterized the null phenotypes of UBR4-deficient mice in which the UBR box of UBR4 was deleted. We show that the mutant mice die around embryonic days 9.5-10.5 (E9.5-E10.5) associated with abnormalities in various developmental processes such as neurogenesis and cardiovascular development. These developmental defects are significantly attributed to the inability to maintain cell integrity and adhesion, which significantly correlates to the severity of null phenotypes. UBR4-loss induces the depletion of many, but not all, proteins from the plasma membrane, suggesting that UBR4 is involved in proteome-wide turnover of cell surface proteins. Indeed, UBR4 is associated with and required to generate the multivesicular body (MVB) which transiently store endocytosed cell surface proteins before their targeting to autophagosomes and subsequently lysosomes. Our results suggest that the N-recognin UBR4 plays a role in the homeostasis of cell surface proteins and, thus, cell adhesion and integrity.

The endoplasmic reticulum-residing chaperone BiP is short-lived and metabolized through N-terminal arginylation.

BiP and other endoplasmic reticulum (ER)-resident proteins are thought to be metabolically stable and to function primarily in the ER lumen. We sought to assess how the abundance of these proteins dynamically fluctuates in response to various stresses and how their subpopulations are relocated to non-ER compartments such as the cytosol. We showed that the molecular chaperone BiP (also known as GRP78) was short-lived under basal conditions and ER stress. The turnover of BiP was in part driven by its amino-terminal arginylation (Nt-arginylation) by the arginyltransferase ATE1, which generated an autophagic N-degron of the N-end rule pathway. ER stress elicited the formation of R-BiP, an effect that was increased when the proteasome was also inhibited. Nt-arginylation correlated with the cytosolic relocalization of BiP under the types of stress tested. The cytosolic relocalization of BiP did not require the functionality of the unfolded protein response or the Sec61- or Derlin1-containing translocon. A key inhibitor of the turnover and Nt-arginylation of BiP was HERP (homocysteine-responsive ER protein), a 43-kDa ER membrane-integrated protein that is an essential component of ER-associated protein degradation. Pharmacological inhibition of the ER-Golgi secretory pathway also suppressed R-BiP formation. Finally, we showed that cytosolic R-BiP induced by ER stress and proteasomal inhibition was routed to autophagic vacuoles and possibly additional metabolic fates. These results suggest that Nt-arginylation is a posttranslational modification that modulates the function, localization, and metabolic fate of ER-resident proteins.

Risk factors and outcomes of acute lower gastrointestinal bleeding in intestinal Behçet's disease.

BACKGROUND: Intestinal Behçet's disease (BD) can cause acute lower gastrointestinal bleeding, which is sometimes fatal. AIM: We aimed to identify the risk factors and outcomes of acute lower gastrointestinal bleeding and factors associated with rebleeding in intestinal BD patients. METHODS: Of the total of 588 intestinal BD patients, we retrospectively reviewed the medical records of 66 (11.2%) patients with acute lower gastrointestinal bleeding and compared them with those of 132 matched patients without bleeding. RESULTS: The baseline characteristics were comparable between the bleeding group (n = 66) and the non-bleeding group (n = 132). On multivariate analysis, the independent factors significantly associated with lower gastrointestinal bleeding were older age (>52 years) (hazard ratio [HR] 2.2, 95% confidence interval [CI] 1.058-4.684, p = 0.035) and a nodular ulcer margin (HR 7.1, 95% CI 2.084-24.189, p = 0.002). Rebleeding occurred in 23 patients (34.8%). Female patients (p = 0.044) and those with previous use of corticosteroids or azathioprine (p = 0.034) were more likely to develop rebleeding. On multivariate analysis, only use of steroids or azathioprine was significantly associated with rebleeding (HR 3.2, 95% CI 1.070-9.462, p = 0.037). CONCLUSIONS: Age >52 years and the presence of a nodular margin of the ulcer were found to be related to increased risk of bleeding in patients with intestinal BD. Rebleeding is not uncommon and not effectively prevented with currently available medications. Further studies are warranted to identify effective measures to decrease rebleeding in intestinal BD.

Clinical Efficacy of Beclomethasone Dipropionate in Korean Patients with Ulcerative Colitis.

PURPOSE: Our aim was to evaluate the efficacy and safety of oral beclomethasone dipropionate (BDP) in Korean patients with ulcerative colitis (UC). MATERIALS AND METHODS: The medical records of patients with active UC who were treated with BDP were retrospectively reviewed. Partial Mayo Clinic score (pMS) was calculated to determine disease activity. After 4 weeks of therapy, clinical remission, clinical response, and response failure rates were evaluated. Clinical remission was defined as a post-treatment pMS of 0 or 1, clinical response as a decrease of two of three points in pMS and >30% from baseline, and response failure as a lack of clinical response. Also, we considered that clinical remission was included in clinical response. RESULTS: Between July 2013 and April 2015, 95 patients with UC received BDP therapy at our institution (median age, 44 years; range, 12-81 years). After 4 weeks of therapy, clinical remission and clinical response rates were 50.5% and 73.7%, respectively. Mean change of pMS before and after BDP therapy was 2.4. There was no significant side effect reported. In multivariate analysis, disease activity was the only factor associated with a favorable response. Clinical remission rate was significantly higher in the mild disease activity group (66.7%) than that in the moderate or severe disease activity group (41.9%) (p=0.024). CONCLUSION: BDP is efficacious in inducing a clinical response or remission in Korean patients with UC. Patients with mild UC were more likely to be in remission than those with moderate or severe UC after receiving BDP for 4 weeks. BDP exhibited a good safety profile.

Modulation of SQSTM1/p62 activity by N-terminal arginylation of the endoplasmic reticulum chaperone HSPA5/GRP78/BiP.

The N-end rule pathway is a proteolytic system, in which single N-terminal residues act as a determinant of a class of degrons, called N-degrons. In the ubiquitin (Ub)-proteasome system, specific recognition components, called N-recognins, recognize N-degrons and accelerate polyubiquitination and proteasomal degradation of the substrates. In this study, we show that the pathway regulates the activity of the macroautophagic receptor SQSTM1/p62 (sequestosome 1) through N-terminal arginylation (Nt-arginylation) of endoplasmic reticulum (ER)-residing molecular chaperones, including HSPA5/GRP78/BiP, CALR (calreticulin), and PDI (protein disulfide isomerase). The arginylation is co-induced with macroautophagy (hereafter autophagy) as part of innate immunity to cytosolic DNA and when misfolded proteins accumulate under proteasomal inhibition. Following cytosolic relocalization and arginylation, Nt-arginylated HSPA5 (R-HSPA5) is targeted to autophagosomes and degraded by lysosomal hydrolases through the interaction of its N-terminal Arg (Nt-Arg) with ZZ domain of SQSTM1. Upon binding to Nt-Arg, SQSTM1 undergoes a conformational change, which promotes SQSTM1 self-polymerization and interaction with LC3, leading to SQSTM1 targeting to autophagosomes. Cargoes of R-HSPA5 include cytosolic misfolded proteins destined to be degraded through autophagy. Here, we discuss the mechanisms by which the N-end rule pathway regulates SQSTM1-dependent selective autophagy.