Eun-Ji Park

White adipose tissue (WAT) dysfunction under nutrient excess is a central driver of obesity and its related metabolic disorders. Maintaining precise regulation of adipogenesis and lipid metabolism in WAT is essential for systemic energy balance and metabolic health. Here, we identify Ssu72 phosphatase as a critical regulator of adipogenesis required for WAT expansion. Ssu72 expression is elevated in obese WAT. Notably, adipocyte-specific deletion of Ssu72 in mice confers resistance to high-fat diet (HFD)-induced obesity, accompanied by improved insulin sensitivity and altered energy expenditure. Ssu72 deficiency diminishes HFD-induced adipocyte hypertrophy and inflammation in WAT. Mechanistically, loss of Ssu72 inhibits PPARγ-mediated adipogenesis and lipid storage by hyperphosphorylation of GSK3β, resulting in suppression of WAT expansion. In addition, metabolic alterations in Ssu72-deleted WAT are reversed by restoring Ssu72 expression. Taken together, our findings reveal a novel adipocyte Ssu72-GSK3β axis that regulates obesogenic adipogenesis in white adipocytes, suggesting that Ssu72 is a promising target for controlling diet-induced obesity and whole-body metabolic homeostasis.

Ubiquitination serves a critical role in regulating both inflammatory responses and kidney injury. Among inherited renal disorders, autosomal dominant polycystic kidney disease (ADPKD) has demonstrated associations with disrupted ubiquitin signaling that exacerbates inflammation and cyst progression. In this study, we demonstrate that the E3 ligase Pellino1 (Peli1) acts as an essential contributor to the pathogenesis of ADPKD amid inflammatory conditions. In individuals with clear cell renal cell carcinoma (ccRCC), Peli1 exhibits markedly elevated expression, and this upregulation is associated with adverse clinical outcomes. Additionally, we find that various TLR stimulations in renal tubular cells induce increased Peli1 expression, which is also elevated in samples from ADPKD patients. Using doxycycline-inducible Peli1-transgenic mice, we establish that Peli1 overexpression leads to impaired renal function and facilitates cyst formation. On a mechanistic level, elevated Peli1 promotes cystic epithelial cell proliferation by activating mTOR signaling, accomplished through the stabilization of S6K1. In summary, our data indicate that TLR-driven upregulation of Peli1 facilitates renal cyst growth via S6K1 stabilization. These results reveal a novel mechanistic link between PKD and ccRCC.

Soluble receptors are soluble forms of receptors found in the extracellular space. They have emerged as pivotal regulators of cellular signaling and disease pathogenesis. This review emphasizes their significance in cancer as diagnostic/prognostic markers and potential therapeutic targets. We provide an overview of the mechanisms by which soluble receptors are generated along with their functions. By exploring their involvement in cancer progression, metastasis, and immune evasion, we highlight the importance of soluble receptors, particularly soluble cytokine receptors and immune checkpoints, in the tumor microenvironment. Although current research has illustrated the emerging clinical relevance of soluble receptors, their therapeutic applications remain underexplored. As the landscape of cancer treatment evolves, understanding and targeting soluble receptors might pave the way for novel strategies for cancer diagnosis, prognosis, and therapy.

Changes in the DNA damage response (DDR) and cellular metabolism are two important factors that allow cancer cells to proliferate. DDR is a set of events in which DNA damage is recognized, DNA repair factors are recruited to the site of damage, the lesion is repaired, and cellular responses associated with the damage are processed. In cancer, DDR is commonly dysregulated, and the enzymes associated with DDR are prone to changes in ubiquitination. Additionally, cellular metabolism, especially glycolysis, is upregulated in cancer cells, and enzymes in this metabolic pathway are modulated by ubiquitination. The ubiquitin–proteasome system (UPS), particularly E3 ligases, act as a bridge between cellular metabolism and DDR since they regulate the enzymes associated with the two processes. Hence, the E3 ligases with high substrate specificity are considered potential therapeutic targets for treating cancer. A number of small molecule inhibitors designed to target different components of the UPS have been developed, and several have been tested in clinical trials for human use. In this review, we discuss the role of ubiquitination on overall cellular metabolism and DDR and confirm the link between them through the E3 ligases NEDD4, APC/C^CDH1, FBXW7, and Pellino1. In addition, we present an overview of the clinically important small molecule inhibitors and implications for their practical use.

Supplementary Data from The Pellino1–PKCθ Signaling Axis Is an Essential Target for Improving Antitumor CD8+ T-lymphocyte Function

Supplementary Data from The Pellino1–PKCθ Signaling Axis Is an Essential Target for Improving Antitumor CD8+ T-lymphocyte Function

Supplementary Figure from The Pellino1–PKCθ Signaling Axis Is an Essential Target for Improving Antitumor CD8+ T-lymphocyte Function

CD8+ T cells play an important role in the elimination of tumors. However, the underlying mechanisms involved in eliciting and maintaining effector responses in CD8+ T cells remain to be elucidated. Pellino1 (Peli1) is a receptor signal-responsive ubiquitin E3 ligase, which acts as a critical mediator for innate immunity. Here, we found that the risk of developing tumors was dependent on Peli1 expression. Peli1 was upregulated in CD8+ T cells among tumor-infiltrating lymphocytes (TIL). In contrast, a deficit of Peli1 enhanced the maintenance and effector function of CD8+ TILs. The development of Peli1-deficient CD8+ TILs prevented T-cell exhaustion and retained the hyperactivated states of T cells to eliminate tumors. We also found that Peli1 directly interacted with protein kinase C-theta (PKCθ), a central kinase in T-cell receptor downstream signal transduction, but whose role in tumor immunology remains unknown. Peli1 inhibited the PKCθ pathway by lysine 48–mediated ubiquitination degradation in CD8+ TILs. In summary, the Peli1–PKCθ signaling axis is a common inhibitory mechanism that prevents antitumor CD8+ T-cell function, and thus targeting Peli1 may be a useful therapeutic strategy for improving cytotoxic T-cell activity.

Supplementary Data from The Pellino1–PKCθ Signaling Axis Is an Essential Target for Improving Antitumor CD8+ T-lymphocyte Function

Supplementary Data from The Pellino1–PKCθ Signaling Axis Is an Essential Target for Improving Antitumor CD8+ T-lymphocyte Function