TRIM32 promotes inflammatory responses in rheumatoid arthritis fibroblast‐like synoviocytes

AMBRA1 promotes intestinal inflammation by antagonizing PP4R1/PP4c mediated IKK dephosphorylation in an autophagy-independent manner

IκB kinase (IKK) complex is central regulators of the NF-κB pathway, and dysregulation of IKK phosphorylation leads to hyperactivation of proinflammatory response in various chronic inflammatory diseases, including inflammatory bowel disease (IBD). However, the dynamic modulation of IKK phosphorylation and dephosphorylation in intestinal inflammation remains uncharacterized. Here, we found that autophagy/beclin-1 regulator 1 (AMBRA1) was highly expressed in inflamed colons in a colitis mouse model and in clinical IBD samples. Importantly, AMBRA1 deletion significantly decreased proinflammatory cytokine expression and enhanced the therapeutic effect of infliximab on intestinal inflammation. Mechanistically, the N-term F1 domain of AMBRA1 was required for AMBRA1 to competitively interact with protein phosphatase 4 regulatory subunit 1 (PP4R1) and catalytic protein phosphatase 4 (PP4c) to suppress their interactions with IKK, promote the dissociation of the PP4R1/PP4c complex, and antagonize the dephosphorylation activity of this complex towards the IKK complex. In response to TNF-α stimulation, IKKα phosphorylates AMBRA1 at S1043 to stabilize AMBRA1 expression by impairing its binding to Cullin4A (CUL4A) to decrease its CUL4A-mediated K48-linked ubiquitination. Overall, our study identifies an autophagy-independent function of AMBRA1 as a positive modulator of IKK phosphorylation to promote intestinal inflammation, thus providing a new targeted therapeutic strategy for patients with refractory IBD.

TRIM32 Inhibits NEK7 Ubiquitylation-Dependent Microglia Pyroptosis After Spinal Cord Injury

Spinal cord injury (SCI) is a disabling disease associated with microglial activation. Tripartite motif containing 32 (TRIM32) is an E3 ubiquitin ligase that plays a role in SCI. This study aimed to explore the role of TRIM32 in SCI and its potential mechanisms. We established an SCI mouse model to assess the function of TRIM32 using quantitative real-time polymerase chain reaction (qPCR), and hematoxylin and eosin staining. Additionally, a lipopolysaccharides (LPS)-induced cell injury model was generated to explore the impact of TRIM32 on pyroptosis using qPCR, propidium iodide staining, and western blotting. The ubiquitylation of NEK7 was analyzed using western blotting, co-immunoprecipitation, and immunofluorescence staining. The results showed that TRIM32 expression was increased in SCI mice and LPS-induced BV-2 cells. Overexpression of TRIM32 ameliorated SCI in mice and suppressed pyroptosis in LPS-treated BV-2 cells. Additionally, the E3 ligase TRIM32 promoted the ubiquitylation of NEK7 at the K64 site, leading to the downregulation of NEK7 levels. Inhibiting NEK7 ubiquitylation reversed the suppression of pyroptosis by TRIM32. In conclusion, TRIM32 inhibits microglia pyroptosis by facilitating the ubiquitylation of NEK7 at the K64 site, thereby alleviating the progression of SCI. The findings suggest that TRIM32 has the potential to be a therapeutic target of SCI.

Elucidating the role of ubiquitination and deubiquitination in osteoarthritis progression

Osteoarthritis is non-inflammatory degenerative joint arthritis, which exacerbates disability in elder persons. The molecular mechanisms of osteoarthritis are elusive. Ubiquitination, one type of post-translational modifications, has been demonstrated to accelerate or ameliorate the development and progression of osteoarthritis via targeting specific proteins for ubiquitination and determining protein stability and localization. Ubiquitination process can be reversed by a class of deubiquitinases via deubiquitination. In this review, we summarize the current knowledge regarding the multifaceted role of E3 ubiquitin ligases in the pathogenesis of osteoarthritis. We also describe the molecular insight of deubiquitinases into osteoarthritis processes. Moreover, we highlight the multiple compounds that target E3 ubiquitin ligases or deubiquitinases to influence osteoarthritis progression. We discuss the challenge and future perspectives via modulation of E3 ubiquitin ligases and deubiquitinases expression for enhancement of the therapeutic efficacy in osteoarthritis patients. We conclude that modulating ubiquitination and deubiquitination could alleviate the osteoarthritis pathogenesis to achieve the better treatment outcomes in osteoarthritis patients.

An update on the role of TRIM/NLRP3 signaling pathway in atherosclerosis

Atherosclerosis (AS) is a chronic inflammatory disease of large and medium arteries that includes lipid metabolism disorder and recruitment of immune cells to the artery wall. An increasing number of studies have confirmed that inflammasome over-activation is associated with the onset and progression of atherosclerosis. The NLRP3 inflammasome, in particular, has been proven to increase the incidence rate of cardiovascular diseases (CVD) by promoting pro-inflammatory cytokine release and reducing plaque stability. The strict control of inflammasome and prevention of excessive inflammatory reactions have been the research focus of inflammatory diseases. Tripartite motif (TRIM) is a protein family with a conservative structure and rapid evolution. Several studies have demonstrated the TRIM family's regulatory role in mediating inflammation. This review aims to clarify the relationship between TRIMs and NLRP3 inflammasome and provide insights for future research and treatment discovery.

Overexpression of TRIM32 promotes pancreatic β-cell autophagic cell death through Akt/mTOR pathway under high glucose conditions

Type 2 diabetes mellitus (T2DM) is a growing worldwide epidemic and is characterized by progressive pancreatic β-cell dysfunction and insulin resistance. Tripartite motif protein 32 (TRIM32) belongs to the TRIM family protein and has been shown to be involve in insulin resistance in skeletal muscle and the liver. However, the effect of TRIM32 on pancreatic β-cell dysfunction and its mechanism remains unknown. In the current study, we found that serum TRIM32 concentrations of T2DM in patients were significantly elevated compared to those in healthy controls, which indicated that TRIM32 might be used as a diagnostic biomarker in T2DM patients. In INS-1 cells, exposure to high glucose (HG) conditions caused a significant elevation in TRIM32 expression and TRIM32 was located in the nucleus. Overexpression of TRIM32 in INS-1 cells exacerbated the effects of HG-induced autophagy and impaired insulin secretion. In contrast, the silencing of TRIM32 produced the opposite effect. Furthermore, TRIM32 overexpression decreased the phosphorylation levels of Akt and mTOR under HG conditions. However, the activation of Akt/mTOR by MHY1485 reversed the effects of TRIM32 on HG-treated INS-1 cells. Collectively, the present results suggested that TRIM32 participates in the development of T2DM by modulating autophagic cell death and insulin secretion, which might occur through the Akt/mTOR pathway. Thus, TRIM32 might be a promising target in T2DM therapy.

Notoginsenoside R1 (NG-R1) Promoted Lymphatic Drainage Function to Ameliorating Rheumatoid Arthritis in TNF-Tg Mice by Suppressing NF-κB Signaling Pathway

Rheumatoid arthritis (RA) is a chronic autoimmune disease that is primarily characterized by synovial inflammation. Our previous studies demonstrated that the lymphatic system is critical for the development and maintenance of RA disease, and sufficient lymph drainage helps to improve joint inflammation. In this study, we found that NG-R1, the main active component in the traditional Chinese medicinal herb Sanchi, activating lymphatic function can attenuate synovial inflammation. According to histopathological staining of ankle sections, NG-R1 significantly decreased the area of inflammation and reduced bone destruction of ankle joints in TNF-Tg mice. Near infrared-indocyanine green (NIR-ICG) lymphatic imaging system has shown that NG-R1 significantly improved the lymphatic drainage function. However, the molecular mechanism of its activity is not properly understood. Our in-depth study demonstrates that NG-R1 reduced the inflammatory cytokine production of lymphatic endothelial cells (LECs) stimulated by TNF-α, and the mechanism ameliorated the phosphorylation of IKKα/β and p65, and the translocation of p65 into the nucleus. In summary, this study proved that NG-R1 promoted lymphatic drainage function to ameliorating rheumatoid arthritis in TNF-Tg mice by suppressing NF-κB signaling pathway.

TRIM32 Inhibition Attenuates Apoptosis, Oxidative Stress, and Inflammatory Injury in Podocytes Induced by High Glucose by Modulating the Akt/GSK-3β/Nrf2 Pathway

Hyperglycemia-induced oxidative stress in podocytes exerts a major role in the pathological process of diabetic nephropathy. Tripartite motif-containing protein 32 (TRIM32) has been reported to be a key protein in the modulation of cellular apoptosis and oxidative stress under various pathological processes. However, whether TRIM32 participates in the regulation of high glucose (HG)-induced injury in podocytes has not been investigated. This work aimed to assess the possible role of TRIM32 in mediating HG-induced apoptosis, oxidative stress, and inflammatory response in podocytes in vitro. Our results showed a marked increase in TRIM32 expression in HG-exposed podocytes and the glomeruli of diabetic mice. Loss-of-function experiments showed that TRIM32 knockdown improves the viability of HG-stimulated podocytes and suppresses HG-induced apoptosis, oxidative stress, and inflammatory responses in podocytes. Further investigation revealed that TRIM32 inhibition enhances the activation of nuclear factor erythroid 2-related factor 2 (Nrf2) signaling, which is associated with the modulation of the Akt/glycogen synthase kinase-3β (GSK-3β) axis in podocytes following HG exposure. However, Akt suppression abrogated the TRIM32 knockdown-mediated activation of Nrf2 in HG-exposed podocytes. Nrf2 knockdown also markedly abolished the protective effects induced by TRIM32 inhibition o in HG-exposed podocytes. In summary, this work demonstrated that TRIM32 inhibition protects podocytes from HG-induced injury by potentiating Nrf2 signaling through modulation of Akt/GSK-3β signaling. The findings reveal the potential role of TRIM32 in mediating podocyte injury during the progression of diabetic nephropathy.

The role of TRIM family proteins in autophagy, pyroptosis, and diabetes mellitus

The ubiquitin-proteasome system, which is one of the systems for cell protein homeostasis and degradation, happens through the ordered and coordinated action of three types of enzymes, E1 ubiquitin-activating enzyme, E2 ubiquitin-carrier enzyme, E3 ubiquitin-protein ligase. Tripartite motif-containing (TRIM) family proteins are the richest subfamily of really interesting new gene E3 ubiquitin ligases, which play a critical role not only in many biological processes, including proliferation, apoptosis, pyroptosis, innate immunity, and autophagy, but also many diseases like cancer, diabetes mellitus, and neurodegenerative disease. Increasing evidence suggests that TRIM family proteins play a vital role in modulating autophagy, pyroptosis, and diabetes mellitus. The aim of this review is to discuss the role of TRIM proteins in the regulation of autophagy, pyroptosis, diabetes mellitus, and diabetic complications.