PATJ inhibits histone deacetylase 7 to control tight junction formation and cell polarity

PDZ domains of PATJ facilitate immunological synapse formation to promote T cell activation

BACKGROUND

The highly organized structures of the immunological synapse (IS) are crucial for T cell activation. PDZ domains might be involved in the formation of the IS by serving as docking sites for protein interactions. In this study, we investigate the role of the PALS1-associated tight junction protein (PATJ), which contains 10 PDZ domains, in the formation of IS and its subsequent impact on T cell activation.

METHODS

To elucidate the function of PATJ, we generated murine models with conditional T cell-specific knockout of Patj and assessed T cell activation both in vitro and in vivo within the context of infection and cancer. We employed confocal microscopy to visualize the formation of IS between T cells and antigen-presenting cells in the absence of Patj. A series of PATJ truncations containing different combinations of PDZ domains was used to identify the minimal domain required for effective T cell receptor signaling. The identified active PDZ domain was then incorporated into mesothelin (MSLN)-specific chimeric antigen receptor (CAR) to evaluate its impact on CAR-T cell cytotoxicity against solid tumors.

RESULTS

We observed a rapid increase in PATJ expression during T cell activation. Conditional knockout of Patj in T cells showed impaired immunity against infection and cancer in murine models. Mechanistically, ablation of Patj impedes IS formation, and thus reduces T cell activation. We further showed that engineering the active PDZ domain of PATJ into CAR structure significantly promoted the effector function of CAR-T cells.

CONCLUSIONS

Our study reveals an important role of PATJ in the formation of IS and provides an approach to improve the efficacy of CAR-T therapy.

Proteomic and phosphoproteomic analyses reveal the biological perturbations caused by capsaicin treatment

Capsaicin, the primary active ingredient and irritant in chili peppers, has been utilized across multiple fields as a food adductive or because of its potential anticancer, antioxidant, anti-inflammatory and metabolic regulatory properties. Despite its diverse uses, the mechanism of action of capsaicin has not been fully revealed. Here, we investigated the changes in the proteome and phosphoproteome of A549 cells upon treatment with capsaicin for different durations and at different doses. Pressure cycling technology (PCT) was applied for rapid sample preparation and digestion, significantly improving the stability of phosphorylated proteins and allowing in-depth phosphoproteome analysis within 6 h with protein inputs of 100 μg. Proteomic and phosphoproteomic alterations can be used to accurately identify perturbations caused by various capsaicin doses and exposure durations. Proteomic analysis revealed that capsaicin administration affected the cell cycle and DNA damage pathways in a time- and dose-dependent manner. Compared with the proteomic changes, more sensitive and rapid alterations were observed in the phosphoproteome, a finding further supported by posttranslational modification (PTM) set enrichment analysis (PTM-SEA) of the phosphoproteomic data. The phosphorylation status of serine protein kinase, Aurora kinase A, and Aurora kinase B changed faster than their protein expression. Overall, the findings here identify the proteomic and phosphoproteomic alterations caused by capsaicin, providing new insights for multiomics analysis to elucidate chemical perturbations.

Remote ischemic conditioning slows blood-retinal barrier damage in type 1 diabetic rats

Diabetic retinopathy (DR) is one of the major complications of diabetes and can cause severe visual impairment. Blood-retina barrier (BRB) destruction resulted from chronic hyperglycemia underlines its major pathological process. However, current treatments have limited efficacy and may even cause serious complications. Remote ischemic conditioning (RIC), through repeated transient mechanical occlusion of limb blood vessels, has been confirmed to promote blood-brain barrier integrity after stroke, but its role in BRB disruption has not been elucidated. This study aimed to investigate the protective effects of RIC on the BRB in diabetic rats and its potential mechanisms. 48 Sprague-Dawley rats were randomly assigned to the Sham group, Sham + RIC group, diabetes mellitus (DM) group and DM+RIC group. The diabetic model was successfully induced by intraperitoneal injection of streptozotocin. RIC treatment was administered daily and lasted for 9 weeks. In functional analysis, RIC improved the retinal function based on electroretinogram data and reduced the leakage of BRB in diabetic rats. In proteomic analysis, tight junction pathway was enriched after RIC treatment, in which Patj gene was significantly increased. We also found that RIC increased mRNA levels of Patj, claudin-1 and zonula occludens (ZO)-1, protein expression of claudin-1 when compared with diabetic models. In conclusion, RIC slowed BRB damage in diabetic rats, which may be related to the preservation of tight junction proteins. RIC may be a promising protective strategy for the treatment of DR.

PALS1 is a key regulator of the lateral distribution of tight junction proteins in renal epithelial cells

The evolutionarily conserved apical Crumbs (CRB) complex, consisting of the core components CRB3a (an isoform of CRB3), PALS1 and PATJ, plays a key role in epithelial cell-cell contact formation and cell polarization. Recently, we observed that deletion of one Pals1 allele in mice results in functional haploinsufficiency characterized by renal cysts. Here, to address the role of PALS1 at the cellular level, we generated CRISPR/Cas9-mediated PALS1-knockout MDCKII cell lines. The loss of PALS1 resulted in increased paracellular permeability, indicating an epithelial barrier defect. This defect was associated with a redistribution of several tight junction-associated proteins from bicellular to tricellular contacts. PALS1-dependent localization of tight junction proteins at bicellular junctions required its interaction with PATJ. Importantly, reestablishment of the tight junction belt upon transient F-actin depolymerization or upon Ca2+ removal was strongly delayed in PALS1-deficient cells. Additionally, the cytoskeleton regulator RhoA was redistributed from junctions into the cytosol under PALS1 knockout. Together, our data uncover a critical role of PALS1 in the coupling of tight junction proteins to the F-actin cytoskeleton, which ensures their correct distribution along bicellular junctions and the formation of tight epithelial barrier.