Evaluation of ubiquitinated proteins by proteomics reveals the role of the ubiquitin proteasome system in the regulation of Grp75 and Grp78 chaperone proteins during intestinal inflammation

Corilagin alleviated intestinal ischemia-reperfusion injury by modulating endoplasmic reticulum stress via bonding with Bip

BACKGROUND

Intestinal ischemia-reperfusion (II/R) injury is a common clinical emergency with high morbidity and mortality. Given the absence of efficacious prophylactic and therapeutic interventions and specific drugs, sustained efforts are essential to develop new targeted drugs. Corilagin, a naturally polyphenolic tannic acid widespread in longan, rambutan and many other edible economic crops with medicinal properties in China, is of interest due to its multiple bioactivities, including the potential to mitigate II/R injuries. Nevertheless, a clear understanding of its molecular targets and the intricate mechanisms against II/R injury remains obscure and requires further elucidation.

OBJECTIVE

This study aimed to investigate corilagin's pharmacological impact and molecular mechanism for II/R injury.

METHODS

An animal II/R model was established by clamping superior mesenteric artery (SMA), and the therapeutic efficacy of corilagin against II/R was evaluated by biochemical and pathological analysis. Next, integrated transcriptomic and proteomic analyses was performed to identify key targets. Moreover, endoplasmic reticulum stress (ERS) damage was respectively observed by transmission electron microscope (TEM), immunohistochemistry, TUNEL, flow cytometry and western blotting (WB). Finally, molecular docking, molecular dynamics (MD) simulation, cellular thermal shift assay (CETSA) and drug affinity responsive target stability (DARTS) assays were utilized to assess the interaction between corilagin and binding immunoglobulin protein (Bip, Grp78 or Hspa5), and co-IP assay was conducted to investigate the interaction between Bip and its substrate proteins.

RESULTS

Corilagin exhibited robust protection against II/R injuries, effectively alleviating intestinal tissue damage and oxidative stress induced by II/R. The modulation of ERS as a potential regulatory mechanism was investigated through an integrated transcriptomic and proteomic analysis, identifying Bip as a key target contributing to corilagin's protective effects. Further experimental evidence using molecular docking, MD simulation, CETSA, and DARTS assays confirmed the potentially direct interaction of corilagin with Bip. This interaction promoted the ubiquitin-dependent degradation of the Bip-substrate complex, thereby suppressing ERS-related signalling pathways, including the IRE1 branch, PERK branch, and ATF6 branch, to alleviate tissue damage.

CONCLUSION

This study confirmed that corilagin could selectively bind to Bip, facilitating its ubiquitin-dependent recognition and degradation, thereby inhibiting severe endoplasmic reticulum stress signalling and alleviating II/R injury. A detailed mechanistic insight into the action mode of corilagin had been proposed, supporting its potential usage as an ERS inhibitor.

IP3R1/GRP75/VDAC1 complex mediates endoplasmic reticulum stress-mitochondrial oxidative stress in diabetic atrial remodeling

RATIONALE

Endoplasmic reticulum (ER) stress and mitochondrial dysfunction are important mechanisms of atrial remodeling, predisposing to the development of atrial fibrillation (AF) in type 2 diabetes mellitus (T2DM). However, the molecular mechanisms underlying these processes especially their interactions have not been fully elucidated.

OBJECTIVE

To explore the potential role of ER stress-mitochondrial oxidative stress in atrial remodeling and AF induction in diabetes.

METHODS AND RESULTS

Mouse atrial cardiomyocytes (HL-1 cells) and rats with T2DM were used as study models. Significant ER stress was observed in the diabetic rat atria. After treatment with tunicamycin (TM), an ER stress agonist, mass spectrometry (MS) identified several known ER stress and calmodulin proteins, including heat shock protein family A (HSP70) member [HSPA] 5 [GRP78]) and HSPA9 (GRP75, glucose-regulated protein 75). In situ proximity ligation assay indicated that TM led to increased protein expression of the IP3R1-GRP75-VDAC1 (inositol 1,4,5-trisphosphate receptor 1-glucose-regulated protein 75-voltage-dependent anion channel 1) complex in HL-1 cells. Small interfering RNA silencing of GRP75 in HL-1 cells and GRP75 conditional knockout in a mouse model led to impaired calcium transport from the ER to the mitochondria and alleviated mitochondrial oxidative stress and calcium overload. Moreover, GRP75 deficiency attenuated atrial remodeling and AF progression in Myh6-Cre+/Hspa9flox/flox + TM mice.

CONCLUSIONS

The IP3R1-GRP75-VDAC1 complex mediates ER stress-mitochondrial oxidative stress and plays an important role in diabetic atrial remodeling.

HMGB1-induced asthmatic airway inflammation through GRP75-mediated enhancement of ER-mitochondrial Ca2+ transfer and ROS increased

Imbalanced T-helper (TH)1/Th2 response contributes significantly to asthma pathogenesis. Our study indicated that HMGB1 play an important role in the release of Th2-associated cytokines of asthma. However, the specific mechanism about HMGB1-induced imbalanced TH1/Th2 response is not known. In vivo, an OVA-induced asthma mouse model was set up and mice treated with anti-HMGB1 IgG. The mice treated with the anti-HMGB1 IgG ameliorated airway hyper-reactivity, disruption of Th1/Th2 balance and the upregulation of GRP75 induced by OVA. In vitro, the exposure of normal human bronchial epithelial cells to HMGB1 resulted in the upregulation of GRP75, proinflammatory cytokine production, enhanced ER-Mitochondrial Ca²⁺ transfer, and enhancement of reactive oxygen species (ROS). While HMGB1-induced these changes were attenuated by GRP75 siRNA treatment. Sequentially, pretreatment with 2-APB, SKF960365 (SKF) and Ru360 which inhibit ER-Mitochondrial Ca²⁺ transfer significantly lowered HMGB1-induced the generation of ROS and the release of Th2 cytokines in 16HBE cells. Meanwhile, N-acetylcysteine (NAC) significantly attenuated the HMGB1-mediated pro-inflammatory cytokines release. Therefore, these results indicate that GRP75-mediated ER-Mitochondrial Ca²⁺ transfer may be an important contributor in imbalanced of Th1/Th2 balance of asthma. Moreover, HMGB1 specifically induces the release of Th2 cytokines through GRP75-mediated enhancement of ER-Mitochondrial Ca²⁺ transfer and ROS increased.

Proteomics in Inflammatory Bowel Disease: Approach Using Animal Models

Recently, proteomics studies have provided important information on the role of proteins in health and disease. In the domain of inflammatory bowel disease, proteomics has shed important light on the pathogenesis and pathophysiology of inflammation and has contributed to the discovery of some putative clinical biomarkers of disease activity. By being able to obtain a large number of specimens from multiple sites and control for confounding environmental, genetic, and metabolic factors, proteomics studies using animal models of colitis offered an alternative approach to human studies. Our aim is to review the information and lessons acquired so far from the use of proteomics in animal models of colitis. These studies helped understand the importance of different proteins at different stages of the disease and unraveled the different pathways that are activated or inhibited during the inflammatory process. Expressed proteins related to inflammation, cellular structure, endoplasmic reticulum stress, and energy depletion advanced the knowledge about the reaction of intestinal cells to inflammation and repair. The role of mesenteric lymphocytes, exosomes, and the intestinal mucosal barrier was emphasized in the inflammatory process. In addition, studies in animal models revealed mechanisms of the beneficial effects of some therapeutic interventions and foods or food components on intestinal inflammation by monitoring changes in protein expression and paved the way for some new possible inflammatory pathways to target in the future. Advances in proteomics technology will further clarify the interaction between intestinal microbiota and IBD pathogenesis and investigate the gene-environmental axis of IBD etiology.

SPECT-computed tomography in rats with TNBS-induced colitis: A first step toward functional imaging

AIM

To assess the feasibility of SPECT-computed tomography (CT) in rats with trinitrobenzene sulfonic acid (TNBS)-induced acute colitis and confront it with model inflammatory characteristics.

METHODS

Colitis was induced in Sprague-Dawley rats by intrarectal injection of TNBS (n = 10) while controls received vehicle (n = 10). SPECT-CT with intravenous injection of 10 MBq of 67Ga-Citrate was performed at day 2. SPECT-CT criteria were colon wall thickness and maximal wall signal intensity. Laboratory parameters were assessed: colon weight:length ratio, colon cyclooxygenase-2 expression by western blot and histological inflammatory score.

RESULTS

Colon weight/length ratio, colon COX-2 expression and histological inflammatory score were significantly higher in the TNBS group than in the control group (P = 0.0296, P < 0.0001, P = 0.0007 respectively). Pixel max tend to be higher in the TNBS group than in the control group but did not reach statistical significance (P = 0.0662). Maximal thickness is significantly increased in the TNBS group compared to the control group (P = 0.0016) while colon diameter is not (P = 0.1904). Maximal thickness and colon diameter were correlated to colon COX-2 expression (P = 0.0093, P = 0.009 respectively) while pixel max was not (P = 0.22). Maximal thickness was significantly increased when inflammation was histologically observed (P = 0.0043) while pixel max and colon diameter did not (P = 0.2452, P = 0.3541, respectively).

CONCLUSION

SPECT-CT is feasible and easily distinguished control from colitic rats.

Targeting immunoproteasome and glutamine supplementation prevent intestinal hyperpermeability

BACKGROUND

Intestinal hyperpermeability has been reported in several intestinal and non-intestinal disorders. We aimed to investigate the role of the ubiquitin proteasome system in gut barrier regulation in two mice models: the water avoidance stress model (WAS) and a post-inflammatory model (post-TNBS).

METHODS

Both models were applied in C57BL/6 male mice (n=7-8/group); Proteasome was targeted by injection of a selective proteasome inhibitor or by using knock-out mice for β2i proteasome subunit. Finally, glutamine supplementation was evaluated.

RESULTS

In both models (WAS at day 10, post-TNBS at day 28), we observed an increase in proteasome trypsin-like activity and in inducible β2/constitutive β2 subunit protein expression ratio, associated with an increase in intestinal permeability. Moreover, intestinal hyperpermeability was blunted by intraperitoneal injection of selective proteasome inhibitor in WAS and post-TNBS mice. Of note, knock-out mice for the β2i subunit exhibited a significant decrease in intestinal permeability and fecal pellet output during WAS. Glutamine supplementation also improved colonic permeability in both models.

CONCLUSIONS

In conclusion, the proteasome system is altered in the colonic mucosa of WAS and post-TNBS mice with increased trypsin-like activity. Associated intestinal hyperpermeability was blunted by immunoproteasome inhibition.

2,5-Dimethyl-celecoxib inhibits cell cycle progression and induces apoptosis in human leukemia cells

Cyclooxygenase-2 (COX-2) is an essential regulator of cancer promotion and progression. Extensive efforts to target this enzyme have been developed to reduce growth of cancer cells for chemopreventive and therapeutic reasons. In this context, cyclooxygenase-2 inhibitors present interesting antitumor effects. However, inhibition of COX-2 by anti-COX-2 compounds such as celecoxib was recently associated with detrimental cardiovascular side effects limiting their clinical use. As many anticancer effects of celecoxib are COX-2 independent, analogs such as 2,5-dimethyl-celecoxib (DMC), which lacks COX-2-inhibitory activity, represent a promising alternative strategy. In this study, we investigated the effect of this molecule on growth of hematologic cancer cell lines (U937, Jurkat, Hel, Raji, and K562). We found that this molecule is able to reduce the growth and induces apoptosis more efficiently than celecoxib in all the leukemic cell lines tested. Cell death was associated with downregulation of Mcl-1 protein expression. We also found that DMC induces endoplasmic reticulum stress, which is associated with a decreased of GRP78 protein expression and an alteration of cell cycle progression at the G1/S transition in U937 cells. Accordingly, typical downregulation of c-Myc and cyclin D1 and an upregulation of p27 were observed. Interestingly, for shorter time points, an alteration of mitotic progression, associated with the downregulation of survivin protein expression was observed. Altogether, our data provide new evidence about the mode of action of this compound on hematologic malignancies.

Deacetylation of HSPA5 by HDAC6 leads to GP78-mediated HSPA5 ubiquitination at K447 and suppresses metastasis of breast cancer

Heat-shock protein 5 (HSPA5) is a marker for poor prognosis in breast cancer patients and has an important role in cancer progression, including promoting drug resistance and metastasis. In this study, we identify that the specific lysine residue 447 (K447) of HSPA5 could be modified with polyubiquitin for subsequent degradation through the ubiquitin proteasomal system, leading to the suppression of cell migration and invasion of breast cancer. We further found that GP78, an E3 ubiquitin ligase, interacted with the C-terminal region of HSPA5 and mediated HSPA5 ubiquitination and degradation. Knock down of GP78 significantly increased the expression of HSPA5 and enhanced migration/invasive ability of breast cancer cells. Knock down of histone deacetylase-6 (HDAC6) increased the acetylation of HSPA5 at lysine residues 353 (K353) and reduced GP78-mediated ubiquitination of HSPA5 at K447 and then increased cell migration/invasion. In addition, we demonstrate that E3 ubiquitin ligase GP78 preferentially binds to deacetylated HSPA5. Notably, the expression levels of GP78 inversely correlated with HSPA5 levels in breast cancer patients. Patients with low GP78 expression significantly correlated with invasiveness of breast cancer, advanced tumor stages and poor clinical outcome. Taken together, our results provide new mechanistic insights into the understanding that deacetylation of HSPA5 by HDAC6 facilitates GP78-mediated HSPA5 ubiquitination and suggest that post-translational regulation of HSPA5 protein is critical for HSPA5-mediated metastatic properties of breast cancer.

Glutamine enema regulates colonic ubiquitinated proteins but not proteasome activities during TNBS-induced colitis leading to increased mitochondrial activity

Ubiquitin proteasome system contributes to the regulation of intestinal inflammatory response as its inhibition is associated with tissue damage improvement. We aimed to evaluate whether glutamine is able to limit inflammation by targeting ubiquitin proteasome system in experimental colitis. Colitis was induced in male rats by intrarectal instillation of 2-4-6-trinitrobenzen sulfonic acid (TNBS) at day 1. From day 2 to day 6, rats daily received either an intrarectal instillation of PBS (TNBS/PBS group) or glutamine (TNBS/Gln). Rats were euthanized at day 7 and colonic samples were taken to evaluate ubiqutinated proteins by proteomic approach combining 2D electrophoresis and immunoblots directed against ubiquitin. Results were then confirmed by evaluating total expression of proteins and mRNA levels. Survival rate, TNFα, and IL-1β mRNA were improved in TNBS/Gln compared with TNBS/PBS (p < 0.05). Proteasome activities were affected by TNBS but not by glutamine. We identified eight proteins that were less ubiquitinated in TNBS/PBS compared with controls with no effect of glutamine. Four proteins were more ubiquitinated in TNBS/PBS group and restored in TNBS/Gln group. Finally, 12 ubiquitinated proteins were only affected by glutamine. Among proteins affected by glutamine, eight proteins (GFPT1, Gapdh, Pkm2, LDH, Bcat2, ATP5a1, Vdac1, and Vdac2) were involved in metabolic pathways. In conclusion, glutamine may regulate ubiquitination process during intestinal inflammation.

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Enteral glutamine infusion modulates ubiquitination of heat shock proteins, Grp-75 and Apg-2, in the human duodenal mucosa

Glutamine, the most abundant amino acid in the human body, plays several important roles in the intestine. Previous studies showed that glutamine may affect protein expression by regulating ubiquitin-proteasome system. We thus aimed to evaluate the effects of glutamine on ubiquitinated proteins in human duodenal mucosa. Five healthy male volunteers were included and received during 5 h, on two occasions and in a random order, either an enteral infusion of maltodextrins alone (0.25 g kg(-1) h(-1), control), mimicking carbohydrate-fed state, or maltodextrins with glutamine (0.117 g kg(-1) h(-1), glutamine). Endoscopic duodenal biopsies were then taken. Total cellular protein extracts were separated by 2D gel electrophoresis and analyzed by an immunodetection using anti-ubiquitin antibody. Differentially ubiquitinated proteins were then identified by liquid chromatography-electrospray ionization MS/MS. Five proteins were differentially ubiquitinated between control and glutamine conditions. Among these proteins, we identified two chaperone proteins, Grp75 and hsp74. Grp75 was less ubiquitinated after glutamine infusion compared with control. In contrast, hsp74, also called Apg-2, was more ubiquitinated after glutamine. In conclusion, we provide evidence that glutamine may regulate ubiquitination processes of specific proteins, i.e., Grp75 and Apg-2. Grp75 has protective and anti-inflammatory properties, while Apg-2 indirectly regulates stress-induced cell survival and proliferation through interaction with ZO-1. Further studies should confirm these results in stress conditions.