OBJECTIVE: Obesity-induced kidney injury contributes to the development of diabetic nephropathy (DN). Here, we identified the functions of ubiquitin-specific peptidase 19 (USP19) in HK-2 cells exposed to a combination of high glucose (HG) and free fatty acid (FFA) and determined its association with TGF-beta-activated kinase 1 (TAK1).
METHODS: HK-2 cells were exposed to a combination of HG and FFA. USP19 mRNA expression was detected by quantitative RT-PCR (qRT-PCR), and protein analysis was performed by immunoblotting (IB). Cell growth was assessed by Cell Counting Kit-8 (CCK-8) viability and 5-ethynyl-2\'-deoxyuridine (EdU) proliferation assays. Cell cycle distribution and apoptosis were detected by flow cytometry. The USP19/TAK1 interaction and ubiquitinated TAK1 levels were assayed by coimmunoprecipitation (Co-IP) assays and IB.
RESULTS: In HG+FFA-challenged HK-2 cells, USP19 was highly expressed. USP19 knockdown attenuated HG+FFA-triggered growth inhibition and apoptosis promotion in HK-2 cells. Moreover, USP19 knockdown alleviated HG+FFA-mediated PTEN-induced putative kinase 1 (PINK1)/Parkin pathway inactivation and increased mitochondrial reactive oxygen species (ROS) generation in HK-2 cells. Mechanistically, USP19 stabilized the TAK1 protein through deubiquitination. Importantly, increased TAK1 expression reversed the USP19 knockdown-mediated phenotypic changes and PINK1/Parkin pathway activation in HG+FFA-challenged HK-2 cells.
CONCLUSIONS: The findings revealed that USP19 plays a crucial role in promoting HK-2 cell dysfunction induced by combined stimulation with HG and FFAs by stabilizing TAK1, providing a potential therapeutic strategy for combating DN.

Cervical cancer ranks fourth in female mortality. Since the mechanisms for pathogenesis of cervical cancer are still poorly understood, the effective treatment options are lacking. Beclin-1 exhibits an inhibitory role in cervical cancer via suppressing the proliferation, invasion, and migration of cervical cancer cells. It is reported that USP19 removes the K11-linked ubiquitination of Beclin-1 to protect Beclin-1 from proteasomal degradation. Interestingly, we found that hypoxia induced a significant decrease of both Beclin-1 and USP19, suggesting that hypoxia could dually inhibit the protein level of Beclin-1 through a type 2 coherent feed-forward loop (C2-FFL, hypoxia ⊸ Beclin-1 integrating with hypoxia ⊸ USP19 → Beclin-1) to promote the occurrence and development of cervical cancer. Furthermore, mathematical modeling revealed that under the hypoxic environment of solid tumor, the hypoxia/USP19/Beclin-1 coherent feed-forward loop could significantly reduce the protein level of Beclin-1, greatly enhance the sensitivity of Beclin-1 to hypoxia, strikingly restrict the heterogeneity of Beclin-1, and contribute to the low positive rate of Beclin-1 in cervical cancer. It is expected to have significance for elucidating the underlying mechanisms of the occurrence and development of cervical cancer and to provide novel targets and strategies for prevention and treatment of cervical cancer.

To elucidate the relationship between USP19 and O(6)-methylguanine-DNA methyltransferase (MGMT) after temozolomide treatment in glioblastoma (GBM) patients with chemotherapy resistance.
Screening the deubiquitinase pannel and identifying the deubiquitinase directly interacts with and deubiquitination MGMT. Deubiquitination assay to confirm USP19 deubiquitinates MGMT. The colony formation and tumor growth study in xenograft assess USP19 affects the GBM sensitive to TMZ was performed by T98G, LN18, U251, and U87 cell lines. Immunohistochemistry staining and survival analysis were performed to explore how USP19 is correlated to MGMT in GBM clinical management.
USP19 removes the ubiquitination of MGMT to facilitate the DNA methylation damage repair. Depletion of USP19 results in the glioblastoma cell sensitivity to temozolomide, which can be rescued by overexpressing MGMT. USP19 is overexpressed in glioblastoma patient samples, which positively correlates with the level of MGMT protein and poor prognosis in these patients.
The regulation of MGMT ubiquitination by USP19 plays a critical role in DNA methylation damage repair and GBM patients\' temozolomide chemotherapy response.

Tight control of the type I interferon (IFN) signaling pathway is critical for maintaining host innate immune responses, and the ubiquitination and deubiquitination of signaling molecules are essential for signal transduction. Deubiquitinase ubiquitin-specific protein 19 (USP19) is known to be involved in deubiquitinating Beclin1, TRAF3, and TRIF for downregulation of the type I IFN signaling. Here, we show that SIAH1, a cellular E3 ubiquitin ligase that is involved in multicellular pathway, is a potent positive regulator of virus-mediated type I IFN signaling that maintains homeostasis within the antiviral immune response by targeting USP19. In the early stages of virus infection, stabilized SIAH1 directly interacts with the USP19 and simultaneously mediates K27-linked ubiquitination of 489, 490, and 610 residues of USP19 for proteasomal degradation. Additionally, we found that USP19 specifically interacts with MAVS and deubiquitinates K63-linked ubiquitinated MAVS for negative regulation of type I IFN signaling. Ultimately, we identified that SIAH1-mediated degradation of USP19 reversed USP19-mediated deubiquitination of MAVS, Beclin1, TRAF3, and TRIF, resulting in the activation of antiviral immune responses. Taken together, these findings provide new insights into the molecular mechanism of USP19 and SIAH1, and suggest a critical role of SIAH1 in antiviral immune response and homeostasis.

Hippo pathway plays a crucial role in the progression of hepatocellular carcinoma (HCC), and yes-associated protein (YAP) is one of the major factors of the Hippo pathway. However, the mechanism of abnormal YAP activation in HCC has not been well elucidated. Here, we screened a Deubiquitinating enzymes\' (DUB) siRNA library targeting DUBs, and identified Ubiquitin Specific Peptidase 19 (USP19) as a specific deubiquitinating enzyme of YAP in HCC, which could stabilize YAP at K76 and K90 sites via removing the K48- and K11-linked ubiquitin chains. USP19 knockdown decreased the expression of YAP protein and its target gene (CTGF, CYR61, ANKRD1) expression. Through substantial in vivo and in vitro experiments, we prove that USP19 facilities the proliferation and migration of HCC. More importantly, we found that USP19 was upregulated in HCC tissues and associated with poor prognosis. In general, our research revealed a novel post-translational mechanism between USP19 and YAP in HCC, suggesting that USP19 may be a pivotal therapeutic target for HCC treatment.

Chronic obstructive pulmonary disease (COPD) is commonly caused by smoking. FUN14 domain-containing protein 1 (FUNDC1) plays a fundamental role in mitochondrial autophagy and apoptosis in cigarette smoke extract (CSE)-treated BEAS-2B cells. The present study investigated the mechanism of action of FUNDC1 in mitochondrial dysfunction and apoptosis in CSE-treated BEAS-2B cells. The interaction between ubiquitin-specific peptidase 19 (USP19) and FUNDC1 was analyzed using co-immunoprecipitation. Effects of USP19 knockdown and/or FUNDC1 overexpression on the survival, apoptosis, mitochondrial membrane potential, and oxygen consumption rate (OCR) of BEAS-2B cells treated with 15% CSE were determined. In BEAS-2B cells, CSE inhibited cell survival, promoted apoptosis, increased the expression of USP19 and FUNDC1, increased the ratio of LC3 II to LC3 I (LC3 II/I), and decreased mitochondrial membrane potential and TOM20 levels. In CSE-treated BEAS-2B cells, USP19 knockdown reduced FUNDC1 and LC3 II/I, increased the levels of TOM20, improved cell survival, mitochondrial membrane potential, and OCR, and inhibited apoptosis. USP19 deubiquitinates FUNDC1. FUNDC1 overexpression inhibited the effect of USP19 knockdown in CSE-treated BEAS-2B cells. Overall, decreasing USP19 expression alleviates CSE-induced mitochondrial dysfunction in BEAS-2B cells by downregulating FUNDC1, providing novel insights into the molecular mechanism of FUNDC1 regulation in COPD.

Triple-negative breast cancer (TNBC), a heterogeneous subtype of breast cancer (BC), had poor prognosis. Endoplasmic reticulum (ER) stress was responsible for cellular processes and played a crucial role in the cell function. ER stress is a complex and dynamic process that can induce abnormal apoptosis and death. However, the underlying mechanism of ER stress involved in TNBC is not well defined.
We identified ubiquitin-specific protease 19 (USP19) as a TNBC negative regulator for further investigation. The effects of USP19 on BC proliferation were assessed in vitro using proliferation test and cell-cycle assays, while the effects in vivo were examined using a mouse tumorigenicity model. Through in vitro flow cytometric analyses and in vivo TUNEL assays, cell apoptosis was assessed. Proteomics was used to examine the proteins that interact with USP19.
Multiple in vitro and in vivo tests showed that USP19 decreases TNBC cell growth while increasing apoptosis. Then, we demonstrated that USP19 interacts with deubiquitinates and subsequently stabilises family molecular chaperone regulator 6 (BAG6). BAG6 can boost B-cell lymphoma 2 (BCL2) ubiquitination and degradation, thereby raising ER calcium (Ca2+ ) levels and causing ER stress. We also found that the N6 -methyladenosine (m6 A) \"writer\" methyltransferase-like 14 (METTL14) increased global m6 A modification.
Our study reveals that USP19 elevates the intracellular Ca2+ concentration to alter ER stress via regulation of BAG6 and BCL2 stability and may be a viable therapeutic target for TNBC therapy.

Low-dose lipopolysaccharide (LPS) protects against early brain injury (EBI) after subarachnoid hemorrhage (SAH). However, the mechanism underlying the neuroprotective roles of low-dose LPS remain largely undefined.
A SAH mice model was established and the pathological changes of brain were evaluated by wet-dry weight method, HE and Nissl staining, and blood-brain barrier (BBB) permeability assay. Cell apoptosis and inflammation were monitored by TUNEL, flow cytometry and ELISA assays. qRT-PCR, immunofluorescence and Western blot were used to detect the expression of microglial polarization-related or oxidative stress-associated markers. Bioinformatics analysis, luciferase and ChIP assays were employed to detect the direct association between FOXO1 and IL-10 promoter. The ubiquitination of FOXO1 in the in vitro SAH model was detected by co-IP.
Low-dose LPS alleviated SAH-induced neurological dysfunction, brain edema, BBB disruption, damage in the hippocampus, neuronal apoptosis and inflammation via modulating microglial M1/M2 polarization by IL-10/IL-10R1 signaling. Mechanistic studies showed that FOXO1 acted as a transcriptional activator of IL-10. USP19 mediated the deubiquitination of FOXO1 to activate IL-10/IL-10R1 signaling, thereby regulating microglial M1/M2 polarization. Functional experiments revealed that low-dose LPS upregulated USP19 to modulate microglial M1/M2 polarization via FOXO1/IL-10/IL-10R1 signaling in SAH mice.
Low-dose LPS protected against EBI after SAH by modulating microglial M1/M2 polarization via USP19/FOXO1/IL-10/IL-10R1 signaling.

Survivin is a bifunctional protein that plays crucial roles in tumorigenesis. In the present study, we discovered that the natural product gastrodin suppressed the cell viability and colony formation of non-small cell lung cancer (NSCLC) cell lines A549, HCC827, and H460 in a dose-dependent manner. In addition, gastrodin enhanced the protein levels of cleaved-caspase 3 by activating the endogenous mitochondrial apoptosis pathway. Gastrodin inhibits protein kinase B (Akt)/WEE1/cyclin-dependent kinase 1 (CDK1) signaling to downregulate survivin Thr34 phosphorylation. Survivin Thr34 dephosphorylation caused by gastrodin interfered with the binding of ubiquitin-specific protease 19 (USP19), which eventually destabilized survivin. We revealed that the growth of NSCLC xenograft tumors was markedly suppressed by gastrodin in vivo. Furthermore, gastrodin overcomes pemetrexed resistance in vivo or in vitro. Our results suggest that gastrodin is a potential antitumor agent by reducing survivin in NSCLC.

A recent research paper published in Journal of Cell Biology by Chen and colleagues describes a novel mechanism by which the MAM (Mitochondrial-associated endoplasmic reticulum membrane) protein FUNDC1 (FUN14 domain-containing protein 1) regulates mitochondrial division through altered protein post-translational modifications under hypoxic stress. The authors found that in a hypoxic environment, the endoplasmic reticulum-localized deubiquitinating enzyme USP19 accumulates at the MAM and interacts with the enriched mitochondrial outer membrane protein FUNDC1, which subsequently induces its deubiquitination and promotes the oligomerization and activity of DRP1, and mitochondria eventually divide in the presence of DRP1. This article provides new insights into the regulation of mitochondrial dynamics by FUNDC1 under hypoxic condition.