Human RNASET2 derivatives as potential anti-angiogenic agents: actin binding sequence identification and characterization

Epididymal RNase T2 contributes to astheno-teratozoospermia and intergenerational metabolic disorder through epididymosome-sperm interaction

BACKGROUND

The epididymis is crucial for post-testicular sperm development which is termed sperm maturation. During this process, fertilizing ability is acquired through the epididymis-sperm communication via exchange of protein and small non-coding RNAs (sncRNAs). More importantly, epididymal-derived exosomes secreted by the epididymal epithelial cells transfer sncRNAs into maturing sperm. These sncRNAs could mediate intergenerational inheritance which further influences the health of their offspring. Recently, the linkage and mechanism involved in regulating sperm function and sncRNAs during epididymal sperm maturation are increasingly gaining more and more attention.

METHODS

An epididymal-specific ribonuclease T2 (RNase T2) knock-in (KI) mouse model was constructed to investigate its role in developing sperm fertilizing capability. The sperm parameters of RNase T2 KI males were evaluated and the metabolic phenotypes of their offspring were characterized. Pandora sequencing technology profiled and sequenced the sperm sncRNA expression pattern to determine the effect of epididymal RNase T2 on the expression levels of sperm sncRNAs. Furthermore, the expression levels of RNase T2 in the epididymal epithelial cells in response to environmental stress were confirmed both in vitro and in vivo.

RESULTS

Overexpression of RNase T2 caused severe subfertility associated with astheno-teratozoospermia in mice caput epididymis, and furthermore contributed to the acquired metabolic disorders in the offspring, including hyperglycemia, hyperlipidemia, and hyperinsulinemia. Pandora sequencing showed altered profiles of sncRNAs especially rRNA-derived small RNAs (rsRNAs) and tRNA-derived small RNAs (tsRNAs) in RNase T2 KI sperm compared to control sperm. Moreover, environmental stress upregulated RNase T2 in the caput epididymis.

CONCLUSIONS

The importance was demonstrated of epididymal RNase T2 in inducing sperm maturation and intergenerational inheritance. Overexpressed RNase T2 in the caput epididymis leads to astheno-teratozoospermia and metabolic disorder in the offspring.

RNase T2 in Inflammation and Cancer: Immunological and Biological Views

The RNase T2 family consists of evolutionarily conserved endonucleases that express in many different species, including animals, plants, protozoans, bacteria, and viruses. The main biological roles of these ribonucleases are cleaving or degrading RNA substrates. They preferentially cleave single-stranded RNA molecules between purine and uridine residues to generate two nucleotide fragments with 2'3'-cyclic phosphate adenosine/guanosine terminus and uridine residue, respectively. Accumulating studies have revealed that RNase T2 is critical for the pathophysiology of inflammation and cancer. In this review, we introduce the distribution, structure, and functions of RNase T2, its differential roles in inflammation and cancer, and the perspective for its research and related applications in medicine.

Expression, Location, Clinical Implication, and Bioinformatics Analysis of RNASET2 in Gastric Adenocarcinoma

Background: In addition to exploiting its ribonuclease capacity, Ribonuclease T2 (RNASET2) has been reported to exert anti-angiogenic and anti-tumorigenic effects in several tumors. However, the role of RNASET2 in gastric adenocarcinoma (GAC) remains unclear. The purpose of this study was to explore the expression, location, and clinical implications of RNASET2 in GAC.

Methods: Data of RNASET2 mRNA expression in GAC and normal gastric mucosa tissues were extracted from three GSE series and 388 TCGA samples and reanalyzed. Genome-wide CRISPR/Cas9 proliferation screening datasets were used to investigate cell growth changes after RNASET2 knockout in 19 GAC cell lines. The biological processes involved in RNASET2 were studied by the bioinformatics analysis. Furthermore, the corresponding experiments including immunohistochemical staining, clinicopathological features analysis, survival curve, microvessel density detection, cell viability assay, and colony formation assay were performed to validate the expression and function of RNASET2 in GAC.

Results: An abundance of RNASET2 was present in the fundus glands and pylorus glands of the normal gastric mucosa. RNASET2 mRNA and protein were down-regulated in GAC compared with adjacent non-cancerous or normal gastric mucosa tissues. The expression of RNASET2 mRNA and protein in early GAC was higher than that in advanced GAC. 79/134 gene sets involved in the early GAC pathway were enriched in the RNASET2 mRNA high expression group. Genome-wide shRNA and CRISPR/Cas9 proliferation screening showed that knockdown or knockout of RNASET2 could not significantly promote GAC cell growth. AlamarBlue cell viability assay and colony formation assay in AGS cells further validated these results. Clinicopathologic features and survival analysis demonstrated that RNASET2 protein was significantly correlated with tumor cell differentiation, Lauren's classification, and TM4SF1 protein expression, but not correlated with lymph nodal metastasis and patient's prognosis. Microvessel density detection indicated that no significant correlation was found between the expression of RNASET2 protein and the angiogenesis of GAC.

Conclusions: Down-regulation of RNASET2 in GAC was only the consequence of the GAC, instead of the driver. The expression of RNASET2 could be regarded as a good biomarker for identifying the early stage of GAC.

Overexpression of Murine Rnaset2 in a Colon Syngeneic Mouse Carcinoma Model Leads to Rebalance of Intra-Tumor M1/M2 Macrophage Ratio, Activation of T Cells, Delayed Tumor Growth, and Rejection

Human RNASET2 acts as a powerful oncosuppressor protein in in vivo xenograft-based murine models of human cancer. Secretion of RNASET2 in the tumor microenvironment seems involved in tumor suppression, following recruitment of M1-polarized macrophages. Here, we report a murine Rnaset2-based syngeneic in vivo assay. BALB/c mice were injected with parental, empty vector-transfected or murine Rnaset2-overexpressing mouse C51 or TS/A syngeneic cells and tumor growth pattern and immune cells distribution in tumor mass were investigated. Compared to control cells, mouse Rnaset2-expressing C51 cells showed strong delayed tumor growth. CD86+ M1 macrophages were massively recruited in Rnaset2-expressing C51-derived tumors, with concomitant inhibition of MDSCs and CD206+ M2 macrophages recruitment. At later times, a relevant expansion of intra-tumor CD8+ T cells was also observed. After re-challenge with C51 parental cells, most mice previously injected with Rnaset2-expressing C51 cells still rejected C51 tumor cells, suggesting a Rnaset2-mediated T cell adaptive immune memory response. These results point at T2 RNases as evolutionary conserved oncosuppressors endowed with the ability to inhibit cancer growth in vivo through rebalance of intra-tumor M1/M2 macrophage ratio and concomitant recruitment of adaptive anti-tumor CD8+ T cells.

Phosphatidic Acid Counteracts S-RNase Signaling in Pollen by Stabilizing the Actin Cytoskeleton

S-RNase is the female determinant of self-incompatibility (SI) in pear (Pyrus bretschneideri). After translocation to the pollen tube, S-RNase degrades rRNA and induces pollen tube death in an S-haplotype-specific manner. In this study, we found that the actin cytoskeleton is a target of P. bretschneideri S-RNase (PbrS-RNase) and uncovered a mechanism that involves phosphatidic acid (PA) and protects the pollen tube from PbrS-RNase cytotoxicity. PbrS-RNase interacts directly with PbrActin1 in an S-haplotype-independent manner, causing the actin cytoskeleton to depolymerize and promoting programmed cell death in the self-incompatible pollen tube. Pro-156 of PbrS-RNase is essential for the PbrS-RNase-PbrActin1 interaction, and the actin cytoskeleton-depolymerizing function of PbrS-RNase does not require its RNase activity. PbrS-RNase cytotoxicity enhances the expression of phospholipase D (PbrPLDδ1), resulting in increased PA levels in the incompatible pollen tube. PbrPLDδ1-derived PA initially prevents depolymerization of the actin cytoskeleton elicited by PbrS-RNase and delays the SI signaling that leads to pollen tube death. This work provides insights into the orchestration of the S-RNase-based SI response, in which increased PA levels initially play a protective role in incompatible pollen, until sustained PbrS-RNase activity reaches the point of no return and pollen tube growth ceases.

RNASET2 impairs the sperm motility via PKA/PI3K/calcium signal pathways

Asthenozoospermia is one of the leading causes of male infertility owing to a decline in sperm motility. Herein, we determined if there is a correlation between RNASET2 content on human spermatozoa and sperm motility in 205 semen samples from both asthenozoospermia patients and normozoospermia individuals. RNASET2 content was higher in sperm from asthenozoospermia patients than in normozoospermia individuals. On the other hand, its content was inversely correlated with sperm motility as well as progressive motility. Moreover, the inhibitory effect of RNASET2 on sperm motility was induced by incubating normozoospermic sperm with RNase T2 protein. Such treatment caused significant declines in intracellular spermatozoa PKA activity, PI3K activity and calcium level, which resulted in severely impaired sperm motility, and the sperm motility was largely rescued by cAMP supplementation. Finally, protein immunoprecipitation and mass spectrometry identified proteins whose interactions with RNASET2 were associated with declines in human spermatozoa motility. AKAP4, a protein regulating PKA activity, coimmunoprecipated with RNASET2 and they colocalized with one another in the sperm tail, which might contribute to reduced sperm motility. Thus, RNASET2 may be a novel biomarker of asthenozoospermia. Increases in RNASET2 can interact with AKAP4 in human sperm tail and subsequently reduce sperm motility by suppressing PKA/PI3K/calcium signaling pathways.

Mammalian mitochondrial RNAs are degraded in the mitochondrial intermembrane space by RNASET2

Mammalian mitochondrial genome encodes a small set of tRNAs, rRNAs, and mRNAs. The RNA synthesis process has been well characterized. How the RNAs are degraded, however, is poorly understood. It was long assumed that the degradation happens in the matrix where transcription and translation machineries reside. Here we show that contrary to the assumption, mammalian mitochondrial RNA degradation occurs in the mitochondrial intermembrane space (IMS) and the IMS-localized RNASET2 is the enzyme that degrades the RNAs. This provides a new paradigm for understanding mitochondrial RNA metabolism and transport.

Association of Ribonuclease T2 Gene Polymorphisms With Decreased Expression and Clinical Characteristics of Severity in Crohn's Disease

BACKGROUND & AIMS

Variants in the tumor necrosis factor superfamily member 15 gene (TNFSF15, also called TL1A) have been associated with risk for inflammatory bowel disease (IBD). TL1A affects expression of multiple cytokines to promote mucosal inflammation. Little is known about the TL1A-response pathways that regulate cytokine expression. We investigated T-cell gene expression patterns to determine the mechanisms by which TL1A regulates cytokine production, and whether these associate with outcomes of patients with Crohn's disease (CD).

METHODS

Peripheral T cells isolated from normal donors were cultured with TL1A. We performed gene expression profile analysis by RNA sequencing of subsets of interferon gamma (IFNG)-producing and non-producing cells purified by flow cytometry. Unsupervised hierarchical clustering analysis was used to identify gene expression differences between these subsets. Ribonuclease T2 gene (RNASET2) expression and methylation were assessed by quantitative trait loci analyses. Clinical characteristics of patients (complications, resistance to therapy, and recurrence time) were associated with single nucleotide polymorphisms in RNASET2. We performed motif screening to identify polymorphisms that disrupt transcription factor binding sites. Levels of RNASET2 were knocked down with small interfering RNA in CD4+ T cells and the effect on protein expression was determined by proteomic analysis and cytokine production. Cell aggregation was measured by flow cytometry.

RESULTS

We identified 764 genes with at least a 2-fold difference in TL1A-mediated expression between IFNG-secreting and non-secreting T cells (P < 1 × 10-5). Many of these genes were located near IBD susceptibility variants. RNASET2 was the only IBD risk-associated gene with >5-fold down-regulation in the IFNG-secreting subset. RNASET2 disease risk variants were associated with decreased expression in peripheral and mucosal tissues and DNA hypermethylation in CD patients requiring surgical intervention. RNASET2 disease risk variants were associated in CD patients with more complicated disease or resistance to therapy, defined in part by failed response to treatment, increased length of intestinal resection, shorter time to repeat surgery, and high Rutgeerts score (>2) in postoperative endoscopy. The RNASET2 variant rs2149092 was predicted to disrupt a consensus binding site for the transcription factor ETS within an enhancer region. Expression of RNASET2 correlated with expression of ETS. RNASET2 knockdown in T cells increased expression of IFNG and intercellular adhesion molecule 1 (ICAM1) and induced T-cell aggregation. A blocking antibody against (ILFA1), disrupting the lymphocyte function-associated antigen 1-intercellular adhesion molecule 1 interaction, reduced T-cell production of IFNG.

CONCLUSIONS

We identified decreased expression of RNASET2 as a component of TL1A-mediated increase in production of IFNG and as a potential biomarker for patients with severe CD. Further study of the role of RNASET2 in regulating mucosal inflammation may lead to development of novel therapeutic targets.