TP53RK Drives the Progression of Chronic Kidney Disease by Phosphorylating Birc5

Renal fibrosis is a common characteristic of various chronic kidney diseases (CKDs) driving the loss of renal function. During this pathological process, persistent injury to renal tubular epithelial cells and activation of fibroblasts chiefly determine the extent of renal fibrosis. In this study, the role of tumor protein 53 regulating kinase (TP53RK) in the pathogenesis of renal fibrosis and its underlying mechanisms is investigated. TP53RK is upregulated in fibrotic human and animal kidneys with a positive correlation to kidney dysfunction and fibrotic markers. Interestingly, specific deletion of TP53RK either in renal tubule or in fibroblasts in mice can mitigate renal fibrosis in CKD models. Mechanistic investigations reveal that TP53RK phosphorylates baculoviral IAP repeat containing 5 (Birc5) and facilitates its nuclear translocation; enhanced Birc5 displays a profibrotic effect possibly via activating PI3K/Akt and MAPK pathways. Moreover, pharmacologically inhibiting TP53RK and Birc5 using fusidic acid (an FDA-approved antibiotic) and YM-155(currently in clinical phase 2 trials) respectively both ameliorate kidney fibrosis. These findings demonstrate that activated TP53RK/Birc5 signaling in renal tubular cells and fibroblasts alters cellular phenotypes and drives CKD progression. A genetic or pharmacological blockade of this axis serves as a potential strategy for treating CKDs.

Identification and validation of Birc5 as a novel activated cell cycle program biomarker associated with infiltration of immunosuppressive myeloid-derived suppressor cells in hepatocellular carcinoma

BACKGROUND

Preclinical studies and clinical trials have demonstrated that tumor-intrinsic activation of the cell cycle program impedes anticancer immunotherapy. Identification of cell cycle-related biomarkers may provide novel therapeutic targets to augment the efficacy of immunotherapy in hepatocellular carcinoma (HCC).

METHOD AND RESULTS

Based on the genes related to cell cycle program, two clusters (Cluster 1 and Cluster 2) were detected in HCC patients via non-negative matrix factorization algorithm. Multivariable-adjusted Cox regression analysis indicated that the cell cycle gene-based classification was a significant prognostic factor for predicting the clinical outcome of HCC patients. Cluster 1 showed shorter overall survival time and progression-free interval time was associated with activated cell cycle program, higher infiltration of myeloid-derived suppressor cells (MDSCs) and less sensitivity to immunotherapy. A three-gene prognostic model, including BIRC5, C8G, and SPP1, was constructed to characterize the cell cycle-based classification of HCC, which had strong robustness and a stable predictive performance. Notably, Birc5 was positively correlated with CD11b expression (a MDSC marker) in HCC tissue. Concordant high expression of Birc5 and intratumor infiltration level of MDSCs were correlated with worse prognosis of HCC patients. In vitro, hepatocellular Birc5 overexpression promoted immunosuppressive CD11b+ CD33+ HLA-DR- MDSC expansion from human peripheral blood mononuclear cells. Genetically modified animal model of liver cancer revealed that Birc5 depletion upregulated the genes related to lymphocyte-mediated immunity, natural killer cell-mediated immunity, interferon-gamma production, T-cell activation, and T-cell-mediated cytotoxicity. These results suggest an immunosuppressive function of Birc5 in HCC.

CONCLUSION

Birc5 was a potential biomarker and inducer of intratumor infiltration of MDSCs, which led to T cell exclusion or dysfunction in tumor immune microenvironment, consequently resulting in reduced response to ICIs in HCC.

Machine learning and single cell RNA sequencing analysis identifies regeneration-related hepatocytes and highlights a Birc5-related model for identifying cell proliferative ability

BACKGROUND

Partial hepatectomy (PHx) has been shown to induce rapid regeneration of adult liver under emergency conditions. Therefore, an in-depth investigation of the underlying mechanisms that govern liver regeneration following PHx is crucial for a comprehensive understanding of this process.

METHOD

We analyzed scRNA-seq data from liver samples of normal and PHx-48-hour mice. Seven machine learning algorithms were utilized to screen and validate a gene signature that accurately identifies and predicts this population. Co-immunostaining of zonal markers with BIRC5 to investigate regional characteristics of hepatocytes post-PHx.

RESULTS

Single cell sequencing results revealed a population of regeneration-related hepatocytes. Transcription factor analysis emphasized the importance of Hmgb1 transcription factor in liver regeneration. HdWGCNA and machine learning algorithm screened and obtained the key signature characterizing this population, including a total of 17 genes and the function enrichment analysis indicated their high correlation with cell cycle pathway. It is note-worthy that we inferred that Hmgb1 might be vital in the regeneration-related hepatocytes of PHx_48h group. Parallelly, Birc5 might be closely related to the regulation of liver regeneration, and positively correlated with Hmgb1.

CONCLUSIONS

Our study has identified a distinct population of hepatocytes that are closely associated with liver regeneration. Through machine learning algorithms, we have identified a set of 17 genes that are highly indicative of the regenerative capacity of hepatocytes. This gene signature has enabled us to assess the proliferation ability of in vitro cultured hepatocytes using sequencing data alone.

Ablation of Survivin in T Cells Attenuates Acute Allograft Rejection after Murine Heterotopic Heart Transplantation by Inducing Apoptosis

Although studies in oncology have well explored the pharmacological effects of Birc5, little is known about its role in allogeneic T-cell responses. Therefore, the present study used a mouse model of acute heart allograft rejection to investigate the protective effect and mechanism of conditional knockout of Birc5 in T cells. Survivin (encoded by Birc5) was up-regulated in T cells activated in vivo and in vitro. Deletion of Birc5 in T cells attenuated acute heart allograft rejection by reducing the ratio of effector to naive T cells and Th1 to Tregs. In addition, deletion of Birc5 had no noticeable effect on proliferation but on apoptosis and the secretion of IFN-γ. The results revealed a significant increase in the percentage of Annexin V positive CD4⁺ T cells in the Birc5^-/- group, compared to the WT. Moreover, there was significant increase in early apoptotic alloreactive T cells in Birc5^-/- mice and this was partly mediated by caspase-3. Furthermore, treatment with YM155 inhibited acute heart allograft rejection in vivo and increased T-cell apoptosis in healthy human PBMCs in vitro. The results highlight a potential therapeutic target for the prevention and treatment of acute transplant rejection.

Prolactin Rescues Immature B Cells from Apoptosis-Induced BCR-Aggregation through STAT3, Bcl2a1a, Bcl2l2, and Birc5 in Lupus-Prone MRL/lpr Mice

Self-reactive immature B cells are eliminated through apoptosis by tolerance mechanisms, failing to eliminate these cells results in autoimmune diseases. Prolactin is known to rescue immature B cells from B cell receptor engagement-induced apoptosis in lupus-prone mice. The objective of this study was to characterize in vitro prolactin signaling in immature B cells, using sorting, PCR array, RT-PCR, flow cytometry, and chromatin immunoprecipitation. We found that all B cell maturation stages in bone marrow express the prolactin receptor long isoform, in both wild-type and MRL/lpr mice, but its expression increased only in the immature B cells of the latter, particularly at the onset of lupus. In these cells, activation of the prolactin receptor promoted STAT3 phosphorylation and upregulation of the antiapoptotic Bcl2a1a, Bcl2l2, and Birc5 genes. STAT3 binding to the promoter region of these genes was confirmed through chromatin immunoprecipitation. Furthermore, inhibitors of prolactin signaling and STAT3 activation abolished the prolactin rescue of self-engaged MRL/lpr immature B cells. These results support a mechanism in which prolactin participates in the emergence of lupus through the rescue of self-reactive immature B cell clones from central tolerance clonal deletion through the activation of STAT3 and transcriptional regulation of a complex network of genes related to apoptosis resistance.

BIRC5 Expression is Regulated in Uterine Epithelium During the Estrous Cycle

Baculoviral inhibitor of apoptosis repeat-containing 5 (Birc5), also known as survivin, is a member of the inhibitor of apoptosis (IAP) family of proteins and regulates the size of tissues through cell division control. The uterus is the most dynamically sized organ among tissues during the estrous cycle. Although Birc5 is expressed in some terminally differentiated cells, the regulation of its expression in the uterus remains unknown. We investigated the regulation of Birc5 expression in the mouse uterus. RT-PCR analysis showed that Birc5 was expressed in various tissues, including the uterus; the expression level of Birc5 was significantly higher at the diestrus stage. Immunohistochemistry and Western blotting analysis revealed that Birc5 was more active in luminal and glandular epithelium than in endometrial stroma. In ovariectomized mice, Birc5 expression in the uterus was gradually increased by estrogen treatment; however, progesterone injection decreased its expression. Estrogen-induced Birc5 expression was blocked by treatment with estrogen receptor antagonist, ICI 182, 780 and progesterone-reduced Birc5 expression was inhibited by the progesterone receptor antagonist RU486. These results suggest that Birc5 expression is dynamically regulated by a combination of estrogen and progesterone via their receptor-mediated signaling.

Epigenetic Changes at the Birc5 Promoter Induced by YM155 in Synovial Sarcoma

YM155 is an anti-cancer therapy that has advanced into 11 different human clinical trials to treat various cancers. This apoptosis-inducing therapy indirectly affects the protein levels of survivin (gene: Birc5), but the molecular underpinnings of the mechanism remain largely unknown. Synovial sarcoma is a rare soft-tissue malignancy with high protein expression of survivin. We investigated whether YM155 would be a viable therapeutic option to treat synovial sarcoma. YM155 therapy was applied to human synovial sarcoma cell lines and to a genetically engineered mouse model of synovial sarcoma. We discovered that YM155 exhibited nanomolar potency against human synovial sarcoma cell lines and the treated mice with synovial sarcoma demonstrated a 50% reduction in tumor volume compared to control treated mice. We further investigated the mechanism of action of YM155 by looking at the change of lysine modifications of the histone tails that were within 250 base pairs of the Birc5 promoter. Using chromatin immunoprecipitation (ChIP)-qPCR, we discovered that the histone epigenetic marks of H3K27 for the Birc5 promoter changed upon YM155 treatment. H3K27me3 and H3K27ac increased, but the net result was decreased Birc5/survivin expression. Furthermore, the combination of molecular events resulted in caspase 3/7/8 upregulation and death of the sarcoma cells.

Survivin inhibits excessive autophagy in cancer cells but does so independently of its interaction with LC3

Survivin expression is pivotal to life and death at the cellular level. For the past decade its pro-survival activity has been attributed to its essential role in cell proliferation and its ability to inhibit apoptosis. However, a growing body of evidence suggests that it may also contribute to cell viability through an as yet undefined role in autophagy. We report that survivin overexpression in osteosarcoma (U2OS) cells is associated with increased LC3-II expression, smaller autophagosomes, enlarged lysosomes and reduced autophagic flux. We also demonstrate that survivin binds LC3 directly through a canonical LC3-interacting region (LIR) in its baculovirus inhibitors of apoptosis protein (IAP) repeat BIR domain, mutation of which inhibits the interaction, but does not abrogate its influence on autophagy. Collectively these data suggest that survivin expression restricts autophagic flux, thereby inhibiting late-stage autophagy and preventing cell death, but does so independently of LC3.

Summary: Survivin binds to LC3 through a canonical LIR, yet this interaction is not required for survivin overexpression to reduce autophagic flux, suggesting that survivin regulates autophagy via an alternative mechanism.

Cardioprotective Actions of TGFβRI Inhibition Through Stimulating Autocrine/Paracrine of Survivin and Inhibiting Wnt in Cardiac Progenitors

Heart failure due to myocardial infarction (MI) is a major cause of morbidity and mortality in the world. We found previously that A83-01, a TGFβRI inhibitor, could facilitate cardiac repair in post-MI mice and induce the expansion of a Nkx2.5 + cardiomyoblast population. This study aimed to investigate the key autocrine/paracrine factors regulated by A83-01 in the injured heart and the mechanism of cardioprotection by this molecule. Using a previously described transgenic Nkx2.5 enhancer-green fluorescent protein (GFP) reporter mice, we isolated cardiac progenitor cells (CPC) including Nkx2.5-GFP + (Nkx2.5+), sca1+, and Nkx2.5+/sca1 + cells. A83-01 was found to induce proliferation of these three subpopulations mainly through increasing Birc5 expression in the MEK/ERK-dependent pathway. Survivin, encoded by Birc5, could also directly proliferate Nkx2.5 + cells and enhance cultured cardiomyocytes viability. A83-01 could also reverse the downregulation of Birc5 in postinjured mice hearts (n = 6) to expand CPCs. Moreover, the increased Wnt3a in postinjured hearts could decrease CPCs, which could be reversed by A83-01 via inhibiting Fzd6 and Wnt1-induced signaling protein 1 expressions in CPCs. Next, we used inducible αMHC-cre/mTmG mice to label cardiomyocytes with GFP and nonmyocytes with RFP. We found A83-01 preserved more GFP + myocytes (68.6% ± 3.1% vs. 80.9% ± 3.0%; p < .05, n = 6) and fewer renewed RFP + myocytes (0.026% ± 0.005% vs. 0.062% ± 0.008%; p < .05, n = 6) in parallel with less cardiac fibrosis in isoprenaline-injected mice treated with A83-01. TGFβRI inhibition in an injured adult heart could both stimulate the autocrine/paracrine activity of survivin and inhibit Wnt in CPCs to mediate cardioprotection and improve cardiac function.

Functional genomics identify Birc5/survivin as a candidate gene involved in the chronotoxicity of cyclin-dependent kinase inhibitors

The circadian timing system orchestrates most of mammalian physiology and behavior in synchrony with the external light/dark cycle. This regulation is achieved through endogenous clocks present in virtually all body cells, where they control key cellular processes, including metabolism, transport, and the cell cycle. Consistently, it has been observed in preclinical cancer models that both the efficacy and toxicity of most chemotherapeutic drugs depend on their time of administration. To further explore the molecular basis underlying the link between the circadian timing system and the cellular response to anticancer drugs, we investigated the circadian transcriptome and CDK inhibitor toxicity in colon mucosa cells. We first show here that among 181 circadian transcripts, approximately 30% of them drive the cell cycle in the healthy mouse colon mucosa, with a majority peaking during the early resting phase. The identification of 26 mitotic genes within this cluster further indicated that the transcriptional coordination of mitosis by the circadian clock participates in the gating of cell division in this tissue. Subsequent selective siRNA-mediated silencing of these 26 targets revealed that low expression levels of the mitotic and anti-apoptotic gene Birc5/survivin significantly and specifically increased the sensitivity of colon epithelial cells to CDK inhibitors. By identifying Birc5/survivin as a potential determinant for the circadian modulation of CDK inhibitor toxicity, these data provide a mechanistic basis for the preclinical development of future CDK inhibitor-based chronotherapeutic strategies.