Biology subjects

Mannion, A. J.

Publications and source records attributed to Mannion, A. J..

4 recordsLinked to original sources

bioRxiv2023

The junctional mechanosensor AmotL2 regulates YAP promotor accessibility

Endothelial cells (ECs) are constantly exposed to mechanical forces in the form of fluid shear stress, extracellular stiffness, and cyclic strain. How these forces are sensed by ECs remains an understudied aspect in the homeostatic regulation of the circulatory system. Angiomotin-like 2 (AmotL2) is localised to EC junctions and is required for alignment and actin reorganisation under conditions of high shear stress. Here we show that AmotL2 crucially regulates transcription and promotor activity of the YAP gene. Functionally, density-dependent proliferation of ECs in vitro and proliferation of a subpopulation of ECs within the inner aortic arch, were both reliant on AmotL2 and Yap/Taz endothelial expression in vivo. Mechanistically, depletion of AmotL2 led to altered nuclear morphology, chromatin accessibility and suppression of YAP-promotor activity through increased H3K27me3 mediated by the polycromb repressive complex component EZH2. Our data describe a previously unknown role for junctional mechanotransduction in shaping the epigenetic landscape and transcriptional regulation of YAP in vascular homeostasis.

cell biology↗

bioRxiv2022

Pro- and anti-tumour activities of CD146/MCAM in breast cancer result from its heterogeneous expression and association with epithelial to mesenchymal transition

CD146, also known as melanoma cell adhesion molecule (MCAM), is expressed in numerous cancers and has been implicated in the regulation of metastasis. We show that CD146 negatively regulates transendothelial migration (TEM) in breast cancer. This tumour suppressor-like activity is supported by a reduction in MCAM gene expression and increased promoter methylation in tumour tissue compared to normal breast tissue. However, increased CD146/MCAM expression is associated with poor prognosis in breast cancer, a characteristic that is difficult to reconcile with inhibition of TEM by CD146 and its epigenetic silencing. Single cell transcriptome data revealed MCAM expression in multiple cell types, including the tumour vasculature and malignant epithelial cells. MCAM expressing tumour cells were in the minority and expression was associated with epithelial to mesenchymal transition (EMT). Furthermore, gene expression signatures defining invasiveness and a stem cell-like phenotype were most strongly associated with mesenchymal-like tumour cells with low levels of MCAM mRNA, likely to represent an intermediate or hybrid E/M state. Our results show that high levels of MCAM gene expression are associated with poor prognosis in breast cancer because they reflect tumour vascularisation and EMT. However, the inhibitory effects of CD146 on TEM are likely to be weakest in an intermediate state between the epithelial and mesenchymal phenotypes, consistent with highly tumourigenic nature of this population.

cancer biology↗

bioRxiv2022

Negative regulation of p53 by the poliovirus receptor PVR is a target of a human cytomegalovirus immune evasion molecule

Initially characterised for its role in maintaining genome integrity, p53 has emerged as a critical hub for coordinating cellular responses to diverse types of stress. Here we identify cell surface receptor loss as a signal for p53 induction. The poliovirus receptor (PVR) regulates angiogenesis, leucocyte adhesion and immune surveillance. We demonstrate that loss of PVR from endothelial cells also promotes cell cycle arrest through the induction of a p53 transcriptional programme. The p53 induction is post-translational and, despite remaining associated with MDM2, p53 exhibits reduced ubiquitination, aiding its stabilisation. Increased expression of PVR marks malignant or infected cells, and retention of PVR in the endoplasmic reticulum by human cytomegalovirus (HCMV) UL141 protein allows HCMV infected cells to evade immunity. We show that intracellular retention of PVR by UL141 prevents p53 induction, allowing HCMV to escape both the immune- and p53-mediated surveillance functions of PVR. These data reveal that p53 coordinates responses to changes in cell surface composition and that the cell intrinsic PVR-p53 pathway coupled with PVR-mediated immune surveillance functions provide a sensor mechanism to maintain expression of this multi-functional cell surface molecule.

cell biology↗

bioRxiv2019

CD99 regulates cancer cell transendothelial migration and endothelial cell function via CDC42 and actin remodelling

Metastasis requires tumour cells to cross endothelial cell (EC) barriers and this occurs using mechanisms similar to those used by extravasating leucocytes during inflammation. The cell surface receptor CD99 is expressed by leucocytes and EC and participates in inflammatory transendothelial migration (TEM). CD99 is also expressed by tumour cells and we have analysed its role in tumour progression and cancer cell TEM. In a xenograft model, CD99 expression inhibited the metastatic progression of human breast cancer. In vitro, tumour cell CD99 was required for adhesion to ECs. However, tumour cell CD99 inhibited the invasion of the endothelial barrier by breast and prostate cancer cells and TEM itself. Furthermore, tumour cell CD99 depletion was associated with cytoskeletal remodelling. Loss of EC CD99 enhanced endothelial barrier function and reduced tumour cell TEM. Mechanistically, CD99 loss enhanced the expression and activity of CDC42, a known cytoskeletal organiser. CDC42 positively regulates EC angiogenic activity and the enhanced CDC42 activity resulting from loss of EC CD99 increased angiogenesis. As a signal transduction hub, CDC42 activity impacts upon many of the hallmarks of cancer. The functional link between CD99 and CDC42 identified here implicates CD99 in regulating these diverse pathways by modulation of CDC42 activity.

cell biology↗