Mapping REV-ERBα’s Protein-Protein Interactions to Understand TH17 Cell Regulation and Inflammation 2258028

HuR—SerpinB9 Axis Regulates Tumor T-Cell Fitness and Persistence via Post-Transcriptional Control 2267776

Findings highlight a HuR-SerpinB9 axis that regulates T-cell senescence and persistence, offering a potential therapeutic target in cancer and autoimmune diseases.

Programmable protein degraders enable selective knockdown of pathogenic β-catenin subpopulations in vitro and in vivo

Aberrant activation of Wnt signaling results in unregulated accumulation of cytosolic β-catenin, which subsequently enters the nucleus and promotes transcription of genes that contribute to cellular proliferation and malignancy. Here, we sought to eliminate pathogenic β-catenin from the cytosol using designer ubiquibodies (uAbs), chimeric proteins composed of an E3 ubiquitin ligase and a target-binding domain that redirect intracellular proteins to the proteasome for degradation. To accelerate uAb development, we leveraged a protein language model–driven algorithm called SaLT&PepPr to computationally design “guide” peptides with affinity for β-catenin, which were subsequently fused to the catalytic domain of a human E3 called carboxyl terminus of Hsp70-interacting protein. Expression of the resulting peptide-guided uAbs in colorectal cancer cells led to the identification of several designs that greatly reduced the abnormally stable pool of free β-catenin in the cytosol and nucleus while preserving the normal membrane–associated subpopulation. This selective knockdown of pathogenic β-catenin suppressed Wnt/β-catenin signaling and impaired tumor cell survival and proliferation. Furthermore, one of the best degraders selectively decreased cytosolic but not membrane-associated β-catenin levels in livers of BALB/c mice following delivery as a lipid nanoparticle–encapsulated mRNA. Collectively, these findings reveal the unique ability of uAbs to selectively deplete abnormal proteins in vitro and in vivo and open the door to peptide-programmable biologic modulators of other disease-causing proteins.

Mechanism of RNA‐Binding Protein ELAVL1 in Promoting Th2 Cell Differentiation Through Stabilizing CPA3 mRNA in Allergic Rhinitis

ABSTRACT This study aimed to elucidate the role of the RNA‐binding protein embryonic lethality abnormal vision‐like protein 1 (ELAVL1) in the pathogenesis of allergic rhinitis (AR), specifically by investigating its potential to promote T helper 2 (Th2) cell differentiation by regulating the stability of carboxypeptidase A3 (CPA3) mRNA. Differentially expressed genes associated with AR were screened via bioinformatic analysis. Nasal mucosal tissues were collected from 42 children with AR and 42 healthy controls. CPA3 was significantly upregulated in the nasal mucosal tissues of AR patients. CD4+ T cells were isolated from the peripheral blood of healthy volunteers, polarized toward Th2 differentiation, and subjected to cell transfection experiments to examine the effect of CPA3 on Th2 differentiation. An ovalbumin (OVA)‐induced AR mouse model was established. Knockdown of CPA3 alleviated nasal symptoms (e.g., scratching and sneezing), attenuated pathological damage in the nasal mucosa (characterized by reduced edema and inflammatory cell infiltration), and suppressed Th2 immune responses (decreased interleukin‐4 and immunoglobulin E levels, reduced Th2 cell proportion, and downregulated GATA binding protein 3 expression) in AR mice. ELAVL1 bound to CPA3 mRNA and enhanced its stability, thereby upregulating CPA3 expression; a positive correlation was observed between their expression levels in AR. Overexpression of CPA3 reversed the alleviating effects of ELAVL1 knockdown on nasal symptoms and Th2 immune responses in AR mice. Taken together, these results demonstrate that targeting the ELAVL1/CPA3 axis may provide a novel therapeutic strategy for AR.

RAS P21 Protein Activator 3 finetunes Type I immunity by limiting HCK-mediated STAT4 phosphorylation

Type I immunity, mediated by IFN-γ, is essential for combating intracellular pathogens but also drives inflammatory diseases. How the immune system balances protective type I responses with pathological inflammation is elusive. While the IL-12-STAT4 pathway that promotes IFN-γ production is well-established, the intrinsic negative regulators remain unclear. We establish that RASA3 serves as a permissive checkpoint for type I immune responses. T cell-specific ablation of RASA3 amplified Th1/Tc1 immunity and IFN-γ expression, enhancing the clearance of Listeria monocytogenes but exacerbating allergic contact dermatitis. We further identify the hematopoietic cell kinase (HCK) as a direct kinase for STAT4, which binds to and phosphorylates it at the Tyr693 residue to elicit IFN-γ production. Mechanistically, RASA3 represses the translation of HCK via constraining ribosomal protein RPL36A expression. Additionally, the RASA3-HCK axis is conserved in human Th1 cells. Thus, we define a critical role of the RASA3-HCK-STAT4 axis in fine-tuning type I immunity and offer promising targets for intervening in Th1/Tc1-driven pathologies. IFN-γ-mediated type I immunity is important for clearing intracellular pathogens yet promotes inflammatory diseases. However, T cell-intrinsic negative regulators controlling IFN-γ expression remain poorly characterized. The authors here identify a role of the RASA3-HCK-STAT4 axis in tempering type I immunity.

ABTB1, as an E3 ubiquitin ligase, suppresses Th17 cell differentiation and mitigates autoimmune inflammation by promoting STAT3 ubiquitination and degradation.

Unconventional role of hydroxymethylglutaryl-CoA synthase 1 in driving pathogenic TH17 cell immunity and autoimmune diseases

T helper 17 (TH17) cells are heterogeneous and able to adopt pathogenic and non-pathogenic phenotypes. Identifying factors controlling pathogenic TH17 cells is of importance for their vital role in inflammation and immune-pathology. Here, we demonstrated that HMGCS1, a cholesterol biosynthesis precursor enzyme, was highly induced by inflammatory cytokines and preferentially expressed by pathogenic TH17 cells in vitro and in vivo. HMGCS1 specifically dictated pathogenic TH17 cell differentiation and augmented autoimmune diseases, yet it has no discernible effect on nonpathogenic TH17 cells. Unexpectedly, this role is independent of its canonical function in cholesterol metabolism but requires its catalytic Cys129 residue. Notably, HMGCS1 governs pTH17 cell generation and pathogenicity by leveraging an IRE1α-XBP1s–dependent ER stress response, which in turn transcriptionally activates the lineage-defining factor RORγt (encoded by Rorc). Mechanistically, HMGCS1 is located to the ER membrane, where it bound and stabilized IRE1α protein. This stabilization is achieved by preventing IRE1α’s interaction with the E3 ubiquitin ligase MARCH5, thereby inhibiting its K48-linked ubiquitination and subsequent degradation. Moreover, interfering with HMGCS1 or the ER stress response in T cells impedes pTH17 immunity and mitigates autoimmune disease in vivo. Therefore, our work unveils a noncanonical axis in which HMGCS1 sustains ER stress to license pTH17 differentiation during autoimmune responses.