Biology subjects

Yap, A.

Publications and source records attributed to Yap, A..

7 recordsLinked to original sources

bioRxiv2026

The way less obvious: PIEZO1 supports apoptotic cell extrusion by optimizing tissue mechanical tension for homeostasis.

Apical cell extrusion is a mechanical process that allows epithelia to eliminate apoptotic cells and prevent inflammation. Mechanosensitive ion channels are often invoked for their capacity to mediate rapid mechanical responses in dynamic morphogenetic processes. Here we report an unexpected strategy for PIEZO1 to support apoptotic extrusion. PIEZO1 inhibition blocks extrusion in cultured cells and zebrafish larvae. However, although PIEZO1 mediates calcium signals during the extrusion process, we show that extrusion is instead antagonized by increase in the preexisting mechanical tension of the epithelium when PIEZO1 is disrupted. Correcting enhanced pre-stress in PIEZO1-disrupted epithelia is sufficient to rescue apoptotic extrusion, even though it does not restore dynamic calcium signals. PIEZO1 supports mechanical homeostasis through a calcium/calcineurin-dependent pathway that protects MYPT1/myosin phosphatase from degradation to limit Myosin II activation. Therefore, PIEZO1 support the morphogenetic process of apoptotic extrusion through mechanical homeostasis.

cell biology↗

bioRxiv2024

Aspergillus fumigatus SidF is a dual substrate acyltransferase involved in biosynthesis of both fusarinine- and ferrichrome-type siderophores

The human pathogen Aspergillus fumigatus produces fusarinine-type (FusTS) and ferrichrome-type siderophores (FchTS), both of which have been shown to be crucial for virulence of this mold. After the common first siderophore biosynthetic step, SidA-catalyzed hydroxylation of ornithine, the pathway splits. For FusTS biosynthesis, SidF incorporates an anhydromevalonyl group, while for FchTS biosynthesis, SidL and an as yet unknown enzyme incorporate an acetyl group. The transacylases SidF and SidL share only limited similarity in their C-terminal GNAT (Gcn5-related N-acetyltransferases) motif-containing domains. SidF is transcriptionally induced by iron limitation and localizes to peroxisomes, whereas SidL is a cytosolic enzyme with largely iron-independent expression. Here, we discovered that simultaneous inactivation of both SidF and SidL abolished the biosynthesis of both FusTS and FchTS and caused a growth defect under iron limitation, similar to the inactivation of SidA. Biosynthesis of both FusTS and FchTS depended on both the unique N-terminal and the GNAT motif-containing C-terminal SidF domains. In conclusion, SidF is the hitherto unknown FchTS biosynthetic enzyme: in contrast to SidL, SidF is a bifunctional enzyme accepting acetyl-CoA and anhydromevalonyl-CoA as substrates for biosynthesis of both FusTS and FchTS. Furthermore, this study revealed interdependence of FusTS and FchTS production, and that the peroxisomal localization of FusTS enzymes is important for optimizing FusTS production at the expense of FchTS. Phylogenetic analyses supported the relevance of these findings to other fungal species and revealed overlapping but distinct consensus sequences for the GNAT motifs of SidL and SidF, most likely reflecting their different substrate specificities. IMPORTANCEAdaptation to the host niche is key for any pathogenic organism. Aspergillus fumigatus is a major fungal pathogen causing 90% of invasive aspergillosis cases, which is associated with a high mortality rate. Siderophore-mediated iron acquisition has been shown to be essential for virulence of A. fumigatus and other fungal pathogens. In recent years, the hyphal siderophore biosynthetic pathway has been largely elucidated with exception of a single unknown enzyme, which we identified here as SidF. In contrast to another siderophore biosynthetic acyltransferase, SidL, SidF is a bifunctional enzyme accepting different substrates. As simultaneous inactivation of SidF and SidL, which share a common protein domain and a common substrate, blocks the biosynthesis of all siderophores, simultaneous targeting of SidF and SidL may allow development of new antifungal drugs. Phylogenetic analyses supported the relevance of these findings to other fungal species Moreover, this study clarified the rational for partial peroxisomal localization of siderophore biosynthesis and their metabolic interdependence. The human pathogen Aspergillus fumigatus produces fusarinine-type (FusTS) and ferrichrome-type siderophores (FchTS), both of which have been shown to be crucial for virulence of this mold. After the common first siderophore biosynthetic step, SidA-catalyzed hydroxylation of ornithine, the pathway splits. For FusTS biosynthesis, SidF incorporates an anhydromevalonyl group, while for FchTS biosynthesis, SidL and an as yet unknown enzyme incorporate an acetyl group. The transacylases SidF and SidL share only limited similarity in their C-terminal GNAT (Gcn5-related N-acetyltransferases) motif-containing domains. SidF is transcriptionally induced by iron limitation and localizes to peroxisomes, whereas SidL is a cytosolic enzyme with largely iron-independent expression. Here, we discovered that simultaneous inactivation of both SidF and SidL abolished the biosynthesis of both FusTS and FchTS and caused a growth defect under iron limitation, similar to the inactivation of SidA. Biosynthesis of both FusTS and FchTS depended on both the unique N-terminal and the GNAT motif-containing C-terminal SidF domains. Taken together, SidF is the hitherto unknown FchTS biosynthetic enzyme: in contrast to SidL, SidF is a bifunctional enzyme accepting acetyl-CoA and anhydromevalonyl-CoA as substrates for biosynthesis of both FusTS and FchTS. Moreover, this study revealed interdependence of FusTS and FchTS production, and that peroxisomal localization of FusTS enzymes is important for optimizing FusTS production at the expense of FchTS.

microbiology↗

bioRxiv2023

Cortical ductility governs cell-cell adhesion mechanics

This paper challenges our understanding of cell-cell adhesion by emphasising the role of mechanical dissipation at the cellular level. We have developed new microdevices to measure the energy dissipated during the rupture of junctions between cell-cell doublets. Using a synthetic cadherin approach, we decoupled the role of cadherin binding energy, signalling and downstream regulation of cytoskeletal architecture. This yielded a phase diagram in which cell junctions transition from a ductile to a brittle fracture mode based on their ratio of cortical tension and shape relaxation time. We recapitulated our results using a descriptive mechanical simulation approach. Our results shift our understanding of cell-cell adhesion from the current focus on bond energy and tension to the key role played by energy dissipation in the cytoskeleton during junction deformation and its active mechanosensitive regulation.

cell biology↗

bioRxiv2023

Co-evolution of spheroid fluidization and mechanical fracture in a morphogenic cascade

Cells migrate and invade tissues during development, immune responses, and cancer. Collective invasion is generally understood to be driven by invading cells unjamming and pushing through barriers such as the extracellular matrix and surrounding tissues. Whether these barriers actively contribute to invasion remains unclear. Using ovarian adenocarcinoma spheroids invading mesothelium derived from benign pleural effusions as an experimental model, combined with modelling, we examine invasion across molecular to multicellular scales. We identify intercellular integrin adhesions linking invasive leader cells to the tissue barrier, triggering apical constrictions within the barrier. This constriction shrinks cell-cell contacts, leading to barrier rupture. Thus, the tissue barrier plays a mechanically active role in invasion. Rather than cells pushing through, we find that coordinated subcellular contractility between the invading leader cell and the barrier drives barrier tensile rupture and invasion, independent of a jamming transition. Together, our findings challenge prevailing paradigms of collective cell invasion.

cell biology↗

bioRxiv2021

Enhanced RhoA signaling stabilizes E-cadherin in migrating epithelial monolayers.

Epithelia migrate as physically coherent populations of cells. Earlier studies revealed that mechanical stress accumulates in these cellular layers as they move. These stresses are characteristically tensile in nature and have often been inferred to arise when moving cells pull upon the cell-cell adhesions that hold them together. We now report that epithelial tension at adherens junctions between migrating cells also reflects an increase in RhoA-mediated junctional contractility. We find that active RhoA levels were stimulated by p114 RhoGEF at the junctions between migrating MCF-7 monolayers, and this is accompanied by increased levels of actomyosin and mechanical tension. By applying a strategy to restore active RhoA specifically at adherens junctions by manipulating its scaffold, anillin, we found that this junctional RhoA signal was necessary to stabilize junctional E-cadherin during epithelial migration. We suggest that stabilization of E-cadherin by RhoA serves to increase cell-cell adhesion against the mechanical stresses of migration.

cell biology↗

bioRxiv2020

A unified view of neighbour cell engagement during apoptotic cell extrusion.

Epithelia must eliminate apoptotic cells to preserve tissue barriers and prevent inflammation [1]. Several different mechanisms exist for apoptotic clearance, including efferocytosis [2, 3] and apical extrusion [4, 5]. We found that extrusion was the first-line response to apoptosis in cultured monolayers and in zebrafish epidermis. During extrusion, the apoptotic cell elicited active lamellipodial protrusions and assembly of a contractile extrusion ring in its neighbours. Depleting E-cadherin compromised both the contractile ring and extrusion, implying that a cadherin-dependent pathway allows apoptotic cells to engage their neighbours for extrusion. We identify RhoA as the cadherin-dependent signal in the neighbour cells and show that it is activated in response to contractile tension from the apoptotic cell. This mechanical stimulus is conveyed by a Myosin VI-dependent mechanotransduction pathway that is necessary both for extrusion and to preserve the epithelial barrier when apoptosis was stimulated. Earlier studies suggested that release of sphingosine-1-phosphate (S1P) from apoptotic cells might define where RhoA was activated. However, we found that although S1P is necessary for extrusion, its contribution does not require a localized source of S1P in the epithelium. We therefore propose a unified view of how RhoA is stimulated to engage neighbour cells for apoptotic extrusion. Here, tension-sensitive mechanotransduction is the proximate mechanism that activates RhoA specifically in the immediate neighbours of apoptotic cells, but this also must be primed by S1P in the tissue environment. Together, these elements provide a coincidence detection system that confers robustness on the extrusion response.

cell biology↗

bioRxiv2018

Probing compression versus stretch activated recruitment of cortical actin and apical junction proteins using mechanical stimulations of suspended doublets.

We report an experimental approach to study the mechanosensitivity of cellcell contact upon mechanical stimulation in suspended cell-doublets. The doublet is placed astride an hourglass aperture, and a hydrodynamic force is selectively exerted on only one of the cells. The geometry of the device concentrates the mechanical shear over the junction area. Together with mechanical shear, the system also allows confocal quantitative live imaging of the recruitment of junction proteins (e.g. E-cadherin, ZO-1, Occludin and actin). We observed the time sequence over which proteins were recruited to the stretched region of the contact. The compressed side of the contact showed no response. We demonstrated how this mechanism polarizes the stress-induced recruitment of junctional components within one single junction. Finally, we demonstrated that stabilizing the actin cortex dynamics abolishes the mechanosensitive response of the junction. Our experimental design provides an original approach to study the role of mechanical force at a cell-cell contact with unprecedented control over stress application and quantitative optical analysis.

biophysics↗