Recent studies have shown the crucial role of podocyte injury in the development of diabetic kidney disease (DKD). Deubiquitinating modification of proteins is widely involved in the occurrence and development of diseases. Here, we explore the role and regulating mechanism of a deubiquitinating enzyme, OTUD5, in podocyte injury and DKD. RNA-seq analysis indicates a significantly decreased expression of OTUD5 in HG/PA-stimulated podocytes. Podocyte-specific Otud5 knockout exacerbates podocyte injury and DKD in both type 1 and type 2 diabetic mice. Furthermore, AVV9-mediated OTUD5 overexpression in podocytes shows a therapeutic effect against DKD. Mass spectrometry and co-immunoprecipitation experiments reveal an inflammation-regulating protein, TAK1, as the substrate of OTUD5 in podocytes. Mechanistically, OTUD5 deubiquitinates K63-linked TAK1 at the K158 site through its active site C224, which subsequently prevents the phosphorylation of TAK1 and reduces downstream inflammatory responses in podocytes. Our findings show an OTUD5-TAK1 axis in podocyte inflammation and injury and highlight the potential of OTUD5 as a promising therapeutic target for DKD.

Colorectal cancer (CRC) remains a major global cause of cancer-related mortality, lacking effective biomarkers and therapeutic targets. Revealing the critical pathogenic factors of CRC and the underlying mechanisms would offer potential therapeutic strategies for clinical application. G protein signaling (RGS) protein family modulators play essential role within regulating downstream signaling of GPCR receptors, with function in cancers unclear. Our study focused on the expression patterns of RGS proteins in CRC, identifying Regulator of G protein signaling 16 (RGS16) as a prospective diagnostic and therapeutic target. Analyzing 899 CRC tissues revealed elevated RGS16 levels, correlating with clinicopathological features and CRC prognosis by immunohistochemistry (IHC) combined with microarray. We confirmed the elevated RGS16 protein level in CRC, and found that patients with RGS16-high tumors exhibited decreased disease-specific survival (DSS) and disease-free survival (DFS) compared to those with low RGS16 expression. Functional assays demonstrated that RGS16 promoted the CRC progression, knockdown of RGS16 led to significantly increased apoptosis rates of CRC in vitro and in vivo. Notably, we also confirmed these phenotypes of RGS16 in organoids originated from resected primary human CRC tissues. Mechanistically, RGS16 restrained JNK/P38-mediated apoptosis in CRC cells through disrupting the recruitment of TAB2/TAK1 to TRAF6. This study provides insights into addressing the challenges posed by CRC, offering avenues for clinical translation.

Chronic inflammation causes muscle wasting. Because most inflammatory cytokine signals are mediated via TGF-β-activated kinase-1 (TAK1) activation, inflammatory cytokine-induced muscle wasting may be ameliorated by the inhibition of TAK1 activity. The present study was undertaken to clarify whether TAK1 inhibition can ameliorate inflammation-induced muscle wasting. SKG/Jcl mice as an autoimmune arthritis animal model were treated with a small amount of mannan as an adjuvant to enhance the production of TNF-α and IL-1β. The increase in these inflammatory cytokines caused a reduction in muscle mass and strength along with an induction of arthritis in SKG/Jcl mice. Those changes in muscle fibers were mediated via the phosphorylation of TAK1, which activated the downstream signaling cascade via NF-κB, p38 MAPK, and ERK pathways, resulting in an increase in myostatin expression. Myostatin then reduced the expression of muscle proteins not only via a reduction in MyoD1 expression but also via an enhancement of Atrogin-1 and Murf1 expression. TAK1 inhibitor, LL-Z1640-2, prevented all the cytokine-induced changes in muscle wasting. Thus, TAK1 inhibition can be a new therapeutic target of not only joint destruction but also muscle wasting induced by inflammatory cytokines.

Heat stress is becoming the major factor regarding dairy cow health and milk quality because of global warming. Circular RNAs (circRNAs) represent a special type of noncoding RNAs, which are related to regulating many biological processes. Nonetheless, little is known concerning their effects on heat-stressed bovine mammary epithelial cells (BMECs). Here, this study found a novel circRNA, circ_002033, using RNA sequencing (RNA-seq) and explored the role and underlying regulatory mechanism in proliferation, apoptosis, and oxidative damage in a heat-stressed bovine mammary epithelial cell line (MAC-T). According to the previous RNA-seq analysis, the abundance of circ_002033 in mammary gland tissue of heat-stressed cows increased relative to nonheat-stressed counterparts. This study found that the knockdown of circ_002033 promoted proliferation and alleviated apoptosis and oxidative damage in heat-stressed MAC-T. Mechanistically, circ_002033 localizes to miR-199a-5p in the cytoplasm of MAC-T to regulate mitogen-activated protein kinase kinase 11 (MAP3K11) expression. Meanwhile, miR-199a-5p and MAP3K11 are also involved in regulating the proliferation and apoptosis of heat-stressed MAC-T. Importantly, circ_002033 knockdown promoted the expression of miR-199a-5p while decreasing that of MAP3K11, thereby enhancing proliferation while alleviating apoptosis and oxidative damage in heat-stressed MAC-T. In summary, we found that circ_002033 regulates the proliferation, apoptosis, and oxidative damage of heat-stressed BMECs through the miR-199a-5p/MAP3K11 axis, providing the theoretical molecular foundation for mitigating heat stress of dairy cows.

Transforming growth factor-β (TGF-β) activated kinase 1 (TAK1), also named mitogen-activated protein kinase 7 (MAPK7), forms a pivotal signaling complex with TAK1-binding proteins (TAB1, TAB2, and TAB3), orchestrating critical biological processes, including immune responses, cell growth, apoptosis, and stress responses. Activation of TAK1 by stimuli, such as tumor necrosis factor α (TNFα), interleukin-1β (IL-1β), and Toll-like receptors (TLRs), underscores its central role in cellular signaling. Given the critical role of the TAK1-binding protein (TAK1-TAB) complex in cellular signaling and its impact on various biological processes, this review seeks to understand how ubiquitination thoroughly regulates the TAK1-TAB complex. This understanding is vital for developing targeted therapies for diseases where this signaling pathway is dysregulated. The exploration is significant as it unveils new insights into the activity, stability, and assembly of the complex, underscoring its therapeutic potential in disease modulation.

BACKGROUND: The innate immune system serves as the first line of host defense. Transforming growth factor-β-activated kinase 1 (TAK1) is a key regulator of innate immunity, cell survival, and cellular homeostasis. Because of its importance in immunity, several pathogens have evolved to carry TAK1 inhibitors. In response, hosts have evolved to sense TAK1 inhibition and induce robust lytic cell death, PANoptosis, mediated by the RIPK1-PANoptosome. PANoptosis is a unique innate immune inflammatory lytic cell death pathway initiated by an innate immune sensor and driven by caspases and RIPKs. While PANoptosis can be beneficial to clear pathogens, excess activation is linked to pathology. Therefore, understanding the molecular mechanisms regulating TAK1 inhibitor (TAK1i)-induced PANoptosis is central to our understanding of RIPK1 in health and disease.
RESULTS: In this study, by analyzing results from a cell death-based CRISPR screen, we identified protein phosphatase 6 (PP6) holoenzyme components as regulators of TAK1i-induced PANoptosis. Loss of the PP6 enzymatic component, PPP6C, significantly reduced TAK1i-induced PANoptosis. Additionally, the PP6 regulatory subunits PPP6R1, PPP6R2, and PPP6R3 had redundant roles in regulating TAK1i-induced PANoptosis, and their combined depletion was required to block TAK1i-induced cell death. Mechanistically, PPP6C and its regulatory subunits promoted the pro-death S166 auto-phosphorylation of RIPK1 and led to a reduction in the pro-survival S321 phosphorylation.
CONCLUSIONS: Overall, our findings demonstrate a key requirement for the phosphatase PP6 complex in the activation of TAK1i-induced, RIPK1-dependent PANoptosis, suggesting this complex could be therapeutically targeted in inflammatory conditions.

BACKGROUND: Inflammation is a key pathological process in bacterial meningitis, and the transforming growth factor-beta-activated kinase 1 (TAK1)/nuclear factor-kappa B (NF-κB) pathway is implicated in the activation of microglia and the production of inflammatory factors. Interleukin (IL)-10 is an anti-inflammatory cytokine acting in an autocrine fashion in macrophages to limit inflammatory responses by decreasing the production of pro-inflammatory cytokines. This paper investigates how IL-10 can inhibit microglia activation and reduce the inflammatory response of nervous system diseases.
METHODS: This study used a pneumococcal-induced in Pneumococcal meningitis (PM) C57BL/6 mice and BV-2 cells model of microglial activation, assessing the effects of IL-10 on the TAK1/NF-κB pathway. The impact of IL-10 on microglial autophagy was investigated through western blot and immunofluorescence. The effects of IL-10 were evaluated by examining cellular activation markers and the activity of molecular signaling pathways (such as phosphorylation levels of TAK1 and NF-κB).
RESULTS: Pneumococcus induced the activation of microglia and reduced IL-10. IL-10 inhibited the TAK1/NF-κB pathway, reducing the pneumococcal-induced inflammatory response in microglia. IL-10 ameliorated pneumococcal infection-induced microglial injury by inhibiting autophagy. Animal experiment results also showed that IL-10 inhibited inflammation and autophagy during Pneumococcal meningitis in mice.
CONCLUSIONS: Our study demonstrates that IL-10 reduces the inflammatory response of microglia by inhibiting the TAK1/NF-κB pathway. Additionally, IL-10 ameliorates pneumococcal infection-induced microglial injury by inhibiting the process of autophagy. These results provide a new theoretical basis and offer new insights for developing strategies to treat bacterial meningitis.

Macrophage-orchestrated inflammation contributes to multiple diseases including sepsis. However, the underlying mechanisms remain to be defined clearly. Here, we show that macrophage TP53-induced glycolysis and apoptosis regulator (TIGAR) is up-regulated in murine sepsis models. When myeloid Tigar is ablated, sepsis induced by either lipopolysaccharide treatment or cecal ligation puncture in male mice is attenuated via inflammation inhibition. Mechanistic characterizations indicate that TIGAR directly binds to transforming growth factor β-activated kinase (TAK1) and promotes tumor necrosis factor receptor-associated factor 6-mediated ubiquitination and auto-phosphorylation of TAK1, in which residues 152-161 of TIGAR constitute crucial motif independent of its phosphatase activity. Interference with the binding of TIGAR to TAK1 by 5Z-7-oxozeaenol exhibits therapeutic effects in male murine model of sepsis. These findings demonstrate a non-canonical function of macrophage TIGAR in promoting inflammation, and confer a potential therapeutic target for sepsis by disruption of TIGAR-TAK1 interaction.

The dysregulation of intensity and duration in innate immunity can result in detrimental effects on the body, emphasizing the crucial need for precise regulation. However, the intricate and accurate nature of innate immunity implies the existence of numerous undiscovered innate immunomodulators, particularly transcription factors. In this study, we have identified a Drosophila C2H2 zinc finger protein CG18262, named Immune-mediated Zinc Finger protein (IMZF), capable of suppressing immune responses of Imd pathway. Mechanistically, IMZF serves as a transcription factor that represses the expression of Imd and Tak1. Intriguingly, our findings also reveal that Relish, an NF-κB transcription factor, positively regulates the expression of IMZF, consequently inhibiting the activation of Imd and Tak1 to prevent an exaggerated immune response. Additionally, we have elucidated the pivotal role played by the Relish-IMZF-Imd/Tak1 axis in restoring immune homeostasis of Drosophila Imd pathway. In summary, our findings not only unveil a novel C2H2 zinc finger immunoregulatory transcription factor, IMZF, along with its specific mechanism of immune regulation, but also shed light on the dual functionality of Relish in different stages of the immune response by modulating distinct effectors. This discovery provides new insights and enlightenment into the complex regulation of Drosophila innate immunity.

Antimicrobial peptides (AMPs), ancient scavengers of bacteria, are very poorly induced in macrophages infected by Mycobacterium tuberculosis (M. tuberculosis), but the underlying mechanism remains unknown. Here, we report that L-alanine interacts with PRSS1 and unfreezes the inhibitory effect of PRSS1 on the activation of NF-κB pathway to induce the expression of AMPs, but mycobacterial alanine dehydrogenase (Ald) Rv2780 hydrolyzes L-alanine and reduces the level of L-alanine in macrophages, thereby suppressing the expression of AMPs to facilitate survival of mycobacteria. Mechanistically, PRSS1 associates with TAK1 and disruptes the formation of TAK1/TAB1 complex to inhibit TAK1-mediated activation of NF-κB pathway, but interaction of L-alanine with PRSS1, disables PRSS1-mediated impairment on TAK1/TAB1 complex formation, thereby triggering the activation of NF-κB pathway to induce expression of AMPs. Moreover, deletion of antimicrobial peptide gene β-defensin 4 (Defb4) impairs the virulence by Rv2780 during infection in mice. Both L-alanine and the Rv2780 inhibitor, GWP-042, exhibits excellent inhibitory activity against M. tuberculosis infection in vivo. Our findings identify a previously unrecognized mechanism that M. tuberculosis uses its own alanine dehydrogenase to suppress host immunity, and provide insights relevant to the development of effective immunomodulators that target M. tuberculosis.