AMOTL2‑knockdown promotes the proliferation, migration and invasion of glioma by regulating β‑catenin nuclear localization

The cellular localization and oncogenic or tumor suppressive effects of angiomiotin-like protein 2 in tumor and normal cells

Angiomiotin (AMOT) family comprises three members: AMOT, AMOT-like protein 1 (AMOTL1), and AMOT-like protein 2 (AMOTL2). AMOTL2 is widely expressed in endothelial cells, epithelial cells, and various cancer cells. Specifically, AMOTL2 predominantly localizes in the cytoplasm and nucleus in human normal cells, whereas associates with cell-cell junctions and actin cytoskeleton in non-human cells, and locates at cell junctions or within the recycling endosomes in cancer cells. AMOTL2 is implicated in regulation of tube formation, cell polarity, and shape, although the specific impact on tumorigenesis remains to be conclusively determined. It has been shown that AMOTL2 enhances tumor growth and metastasis in pancreatic, breast, and colon cancer, however inhibits cell proliferation and migration in lung, hepatocellular cancer, and glioblastoma. In addition to its role in cell shape and cytoskeletal dynamics through co-localization with F-actin, AMOTL2 modulates the transcription of Yes-associated protein (YAP) by binding to it, thereby affecting its phosphorylation and cellular sequestration. Furthermore, the stability and cellular localization of AMOTL2, influenced by its phosphorylation and ubiquitination mediated by specific proteins, affects its cellular function. Additionally, we observe that AMOTL2 is predominantly downregulated in some tumors, but significantly elevated in colorectal adenocarcinoma (COAD). Moreover, overall analysis, GSEA and ROC curve analysis indicate that AMOTL2 exerts as an oncogenic protein in COAD by modulating Wnt pathway, participating in synthesis of collagen formation, and interacting with extracellular matrix receptor. In addition, AMOTL2 potentially regulates the distribution of immune cells infiltration in COAD. In summary, AMOTL2 probably functions as an oncogene in COAD. Consequently, further in-depth mechanistic research is required to elucidate the precise roles of AMOTL2 in various cancers.

Upregulation of Angiomotin-Like 2 Ameliorates Experimental Pulmonary Arterial Hypertension by Inactivating YAP1 Signaling

ABSTRACT

Angiomotin-like 2 (AMOTL2) is related to numerous physiological and pathological conditions by affecting signal transduction. However, whether AMOTL2 is linked to pulmonary arterial hypertension (PAH) has not been addressed. This work aimed to investigate the potential role of AMOTL2 in PAH. A decrease in AMOTL2 abundance was observed in the lungs of PAH rats. The upregulation of AMOTL2 significantly decreased right ventricle systolic pressure and right ventricular hypertrophy in PAH rats. Overexpression of AMOTL2 also led to a noteworthy decrease in vascular wall thickness, pulmonary artery area, and collagen deposition in rats with PAH. AMOTL2 was downregulated in hypoxia-stimulated pulmonary arterial smooth muscle cells (PASMCs). Moreover, AMOTL2 overexpression impeded hypoxia-evoked proliferation, migration, and phenotypic transformation in rat PASMCs. Mechanistic investigation revealed that Yes-associated protein 1 (YAP1) activation in PAH rats or hypoxia-stimulated PASMCs was markedly inhibited by AMOTL2 overexpression, which was associated with increased large tumor suppressor 1/2 phosphorylation. The inhibition of large tumor suppressor 1/2 reversed the AMOTL2-mediated inactivation of YAP1. Restoring the activity of YAP1 reversed the inhibitory effect of AMOTL2 on hypoxia-evoked proliferation, migration, and phenotypic transformation of PASMCs. Collectively, these results suggest that AMOTL2 can ameliorate PAH in a rat model by interfering with pulmonary arterial remodeling via the inactivation of YAP1 signaling. Our work indicates that AMOTL2 may be a candidate target for novel drug development for the treatment of PAH.

The circadian gene ARNTL2 promotes nasopharyngeal carcinoma invasiveness and metastasis through suppressing AMOTL2-LATS-YAP pathway

Metastasis is the major culprit of treatment failure in nasopharyngeal carcinoma (NPC). Aryl hydrocarbon receptor nuclear translocator like 2 (ARNTL2), a core circadian gene, plays a crucial role in the development of various tumors. Nevertheless, the biological role and mechanism of ARNTL2 are not fully elucidated in NPC. In this study, ARNTL2 expression was significantly upregulated in NPC tissues and cells. Overexpression of ARNTL2 facilitated NPC cell migration and invasion abilities, while inhibition of ARNTL2 in similarly treated cells blunted migration and invasion abilities in vitro. Consistently, in vivo xenograft tumor models revealed that ARNTL2 silencing reduced nude mice inguinal lymph node and lung metastases, as well as tumor growth. Mechanistically, ARNTL2 negatively regulated the transcription expression of AMOTL2 by directly binding to the AMOTL2 promoter, thus reducing the recruitment and stabilization of AMOTL2 to LATS1/2 kinases, which strengthened YAP nuclear translocation by suppressing LATS-dependent YAP phosphorylation. Inhibition of AMOTL2 counteracted the effects of ARNTL2 knockdown on NPC cell migration and invasion abilities. These findings suggest that ARNTL2 may be a promising therapeutic target to combat NPC metastasis and further supports the crucial roles of circadian genes in cancer development.

Regulation of YAP and Wnt signaling by the endosomal protein MAMDC4

Maintenance of the intestinal epithelium requires constant self-renewal and regeneration. Tight regulation of proliferation and differentiation of intestinal stem cells within the crypt region is critical to maintaining homeostasis. The transcriptional co-factors β-catenin and YAP are required for proliferation during normal homeostasis as well as intestinal regeneration after injury: aberrant signaling activity results in over proliferation and tumorigenesis. Although both YAP and β-catenin activity are controlled along canonical pathways, it is becoming increasingly clear that non-canonical regulation of these transcriptional regulators plays a role in fine tuning their activity. We have shown previously that MAMDC4 (Endotubin, AEGP), an integral membrane protein present in endosomes, regulates both YAP and β-catenin activity in kidney epithelial cells and in the developing intestinal epithelium. Here we show that MAMDC4 interacts with members of the signalosome and mediates cross-talk between YAP and β-catenin. Interestingly, this cross-talk occurs through a non-canonical pathway involving interactions between AMOT:YAP and AMOT:β-catenin.

Inhibition of exosome biogenesis affects cell motility in heterogeneous sub-populations of paediatric-type diffuse high-grade gliomas

BACKGROUND

Paediatric-type diffuse High-Grade Gliomas (PDHGG) are highly heterogeneous tumours which include distinct cell sub-populations co-existing within the same tumour mass. We have previously shown that primary patient-derived and optical barcoded single-cell-derived clones function as interconnected networks. Here, we investigated the role of exosomes as a route for inter-clonal communication mediating PDHGG migration and invasion.

RESULTS

A comprehensive characterisation of seven optical barcoded single-cell-derived clones obtained from two patient-derived cell lines was performed. These analyses highlighted extensive intra-tumour heterogeneity in terms of genetic and transcriptional profiles between clones as well as marked phenotypic differences including distinctive motility patterns. Live single-cell tracking analysis of 3D migration and invasion assays showed that the single-cell-derived clones display a higher speed and longer travelled distance when in co-culture compared to mono-culture conditions. To determine the role of exosomes in PDHGG inter-clonal cross-talks, we isolated exosomes released by different clones and characterised them in terms of marker expression, size and concentration. We demonstrated that exosomes are actively internalized by the cells and that the inhibition of their biogenesis, using the phospholipase inhibitor GW4689, significantly reduced the cell motility in mono-culture and more prominently when the cells from the clones were in co-culture. Analysis of the exosomal miRNAs, performed with a miRNome PCR panel, identified clone-specific miRNAs and a set of miRNA target genes involved in the regulation of cell motility/invasion/migration. These genes were found differentially expressed in co-culture versus mono-culture conditions and their expression levels were significantly modulated upon inhibition of exosome biogenesis.

CONCLUSIONS

In conclusion, our study highlights for the first time a key role for exosomes in the inter-clonal communication in PDHGG and suggests that interfering with the exosome biogenesis pathway may be a valuable strategy to inhibit cell motility and dissemination for these specific diseases.

AQP8 may affect glioma proliferation and growth by regulating GSK-3β phosphorylation and nuclear transport of β-catenin

PURPOSE

The purpose of this work is to examine the impact of AQP8 on the proliferation and development of human glioma cell lines A172 and U251 and to determine if aquaporin 8 (AQP8) is associated with GSK-3β phosphorylation and nuclear transport of β-catenin in the Wnt signaling pathway.

METHODS

AQP8 knockdown cell lines were constructed using a CRISPR/Cas9 double vector lentivirus infection. SAM/dCas9 was used to construct AQP8 overexpression cell lines and the CV084 lentivirus vector was used to construct AQP8 rescue cell lines. AQP8 and its mRNA, and phosphorylated GSK-3β, β-catenin, and other related proteins, were detected using western blot and qRT-PCR. Glioma cell apoptosis was detected using Hoechst 33342 dye. The migration of glioma cells was discovered using a wound healing assay. β-catenin localization in cells was detected using immunofluorescence staining.

RESULTS

The proliferative and migratory capacities of A172 and U251 cells were significantly enhanced after AQP8 overexpression. The Wnt signaling pathways appeared to have higher levels of phosphorylated GSK-3β and β-catenin, and a rise in the fluorescence intensity ratio of β-catenin in the nucleus and cytoplasm, which suggests that β-catenin translocated into the nucleus, while AQP8 knockdown produced the opposite effect. Further, overexpression of AQP8 in AQP8 knockdown cell lines rescued the reduction of related protein levels caused by AQP8 knockdown.

CONCLUSION

High AQP8 expression promotes proliferation and growth of glioma cells, a process associated with phosphorylation of GSK-3β and nuclear translocation of β-catenin.

The role of Motin family proteins in tumorigenesis-an update

The Motin protein family consists of three members: AMOT (p80 and p130 isoforms), AMOT-like protein 1 (AMOTL1), and AMOT-like protein 2 (AMOTL2). The family members play an important role in processes such as cell proliferation, migration, angiogenesis, tight junction formation, and cell polarity. These functions are mediated through the involvement of the Motins in the regulation of different signal transduction pathways, including those regulated by small G-proteins and the Hippo-YAP pathway. One of the more characterized aspects of Motin family function is their role in regulating signaling through the Hippo-YAP pathway, and while some studies suggest a YAP-inhibitory function other studies indicate the Motins are required for YAP activity. This duality is also reflected in previous reports, often contradictory, that suggest the Motin proteins can function as oncogenes or tumor suppressors in tumorigenesis. In this review we summarize recent findings and integrate that with the existing work describing the multifunctional role of the Motins in different cancers. The emerging picture suggests that the Motin protein function is cell-type and context dependent and that further investigation in relevant cell types and whole organism models is required for the elucidation of the function of this protein family.

AMOTL2 restrains transforming growth factor-β1-induced proliferation and extracellular matrix deposition of airway smooth muscle cells via the down-regulation of YAP1 activation

Angiomotin-like 2 (AMOTL2) is a key modulator of signaling transduction and participates in the regulation of various cellular progresses under diverse physiological and pathological conditions. However, whether AMOTL2 participates in asthma pathogenesis has not been fully studied. In the present work, we studied the possible role and mechanism of AMOTL2 in regulating transforming growth factor-β1 (TGF-β1)-induced proliferation and extracellular matrix (ECM) deposition of airway smooth muscle (ASM) cells. Our results showed marked reductions in the abundance of AMOTL2 in TGF-β1-stimulated ASM cells. Cellular functional investigations confirmed that the up-regulation of AMOTL2 dramatically decreased the proliferation and ECM deposition induced by TGF-β1 in ASM cells. In contrast, the depletion of AMOTL2 exacerbated TGF-β1-induced ASM cell proliferation and ECM deposition. Further research revealed that the overexpression of AMOTL2 restrained the activation of Yes-associated protein 1 (YAP1) in TGF-β1-stimulated ASM cells. Moreover, the reactivation of YAP1 markedly reversed AMOTL2-mediated suppression of TGF-β1-induced ASM cell proliferation and ECM deposition. Together, these findings suggest that AMOTL2 restrains TGF-β1-induced proliferation and ECM deposition of ASM cells by down-regulating YAP1 activation.