TP53INP2 Contributes to TGF-β2-Induced Autophagy during the Epithelial–Mesenchymal Transition in Posterior Capsular Opacification Development

Lens autophagy protein ATG16L1: a potential target for cataract treatment

Rationale: Cataract is the leading cause of blindness and low vision worldwide, yet its pathological mechanism is not fully understood. Although macroautophagy/autophagy is recognized as essential for lens homeostasis and has shown potential in alleviating cataracts, its precise mechanism remains unclear. Uncovering the molecular details of autophagy in the lens could provide targeted therapeutic interventions alongside surgery. Methods: We monitored autophagic activities in the lens and identified the key autophagy protein ATG16L1 by immunofluorescence staining, Western blotting, and transmission electron microscopy. The regulatory mechanism of ATG16L1 ubiquitination was analyzed by co-immunoprecipitation and Western blotting. We used the crystal structure of E3 ligase gigaxonin and conducted the docking screening of a chemical library. The effect of the identified compound riboflavin was tested in vitro in cells and in vivo animal models. Results: We used HLE cells and connexin 50 (cx50)-deficient cataract zebrafish model and confirmed that ATG16L1 was crucial for lens autophagy. Stabilizing ATG16L1 by attenuating its ubiquitination-dependent degradation could promote autophagy activity and relieve cataract phenotype in cx50-deficient zebrafish. Mechanistically, the interaction between E3 ligase gigaxonin and ATG16L1 was weakened during this process. Leveraging these mechanisms, we identified riboflavin, an E3 ubiquitin ligase-targeting drug, which suppressed ATG16L1 ubiquitination, promoted autophagy, and ultimately alleviated the cataract phenotype in autophagy-related models. Conclusions: Our study identified an unrecognized mechanism of cataractogenesis involving ATG16L1 ubiquitination in autophagy regulation, offering new insights for treating cataracts.

Cytoplasmic TP53INP2 acts as an apoptosis partner in TRAIL treatment: the synergistic effect of TRAIL with venetoclax in TP53INP2-positive acute myeloid leukemia

BACKGROUND

Acute myeloid leukemia (AML) is a hematopoietic malignancy with poor outcomes, especially in older AML patients. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is considered a promising anticancer drug because it selectively induces the extrinsic apoptosis of tumor cells without affecting normal cells. However, clinical trials have shown that the responses of patients to TRAIL are significantly heterogeneous. It is necessary to explore predictable biomarkers for the preselection of AML patients with better responsiveness to TRAIL. Here, we investigated the critical role of tumor protein p53 inducible nuclear protein 2 (TP53INP2) in the AML cell response to TRAIL treatment.

METHODS

First, the relationship between TP53INP2 and the sensitivity of AML cells to TRAIL was determined by bioinformatics analysis of Cancer Cell Line Encyclopedia datasets, Cell Counting Kit-8 assays, flow cytometry (FCM) and cell line-derived xenograft (CDX) mouse models. Second, the mechanisms by which TP53INP2 participates in the response to TRAIL were analyzed by Western blot, ubiquitination, coimmunoprecipitation and immunofluorescence assays. Finally, the effect of TRAIL alone or in combination with the BCL-2 inhibitor venetoclax (VEN) on cell survival was explored using colony formation and FCM assays, and the effect on leukemogenesis was further investigated in a patient-derived xenograft (PDX) mouse model.

RESULTS

AML cells with high TP53INP2 expression were more sensitive to TRAIL in vitro and in vivo. Gain- and loss-of-function studies demonstrated that TP53INP2 significantly enhanced TRAIL-induced apoptosis, especially in AML cells with nucleophosmin 1 (NPM1) mutations. Mechanistically, cytoplasmic TP53INP2 maintained by mutant NPM1 functions as a scaffold bridging the ubiquitin ligase TRAF6 to caspase-8 (CASP 8), thereby promoting the ubiquitination and activation of the CASP 8 pathway. More importantly, simultaneously stimulating extrinsic and intrinsic apoptosis signaling pathways with TRAIL and VEN showed strong synergistic antileukemic activity in AML cells with high levels of TP53INP2.

CONCLUSION

Our findings revealed that TP53INP2 is a predictor of responsiveness to TRAIL treatment and supported a potentially individualized therapeutic strategy for TP53INP2-positive AML patients.

TP53INP2 knockdown inhibits inflammatory response and apoptosis after spinal cord injury

BACKGROUND

Spinal cord injury (SCI) is a traumatic neurological disorder with limited therapeutic options. Tumor protein p53-inducible nuclear protein 2 (TP53INP2) is involved in the occurrence and development of various diseases, and it may play a role during SCI via affecting inflammation and neuronal apoptosis. This study investigated the associated roles and mechanisms of TP53INP2 in SCI.

METHODS

Mouse and lipopolysaccharide (LPS)-induced SCI BV-2 cell models were constructed to explore the role of TP53INP2 in SCI and the associated mechanisms. Histopathological evaluation of spinal cord tissue was detected by hematoxylin and eosin staining. The Basso, Beattie, and Bresnahan score was used to measure the motor function of the mice, while the spinal cord water content was used to assess spinal cord edema. The expression of TP53INP2 was measured using RT-qPCR. In addition, inflammatory factors in the spinal cord tissue of SCI mice and LPS-treated BV-2 cells were measured using enzyme-linked immunosorbent assay. Apoptosis and related protein expression levels were detected by flow cytometry and western blot analysis, respectively.

RESULTS

TP53INP2 levels increased in SCI mice and LPS-treated BV-2 cells. The results of in vivo and in vitro experiments showed that TP53INP2 knockdown inhibited the inflammatory response and neuronal apoptosis in mouse spinal cord tissue or LPS-induced BV-2 cells.

CONCLUSIONS

After spinal cord injury, TP53INP2 was upregulated, and TP53INP2 knockdown inhibited the inflammatory response and apoptosis.

The Research Progress in Transforming Growth Factor-β2

Transforming growth factor-beta 2 (TGF-β2), an important member of the TGF-β family, is a secreted protein that is involved in many biological processes, such as cell growth, proliferation, migration, and differentiation. TGF-β2 had been thought to be functionally identical to TGF-β1; however, an increasing number of recent studies uncovered the distinctive features of TGF-β2 in terms of its expression, activation, and biological functions. Mice deficient in TGF-β2 showed remarkable developmental abnormalities in multiple organs, especially the cardiovascular system. Dysregulation of TGF-β2 signalling was associated with tumorigenesis, eye diseases, cardiovascular diseases, immune disorders, as well as motor system diseases. Here, we provide a comprehensive review of the research progress in TGF-β2 to support further research on TGF-β2.