Biology subjects

Flores, T.

Publications and source records attributed to Flores, T..

4 recordsLinked to original sources

bioRxiv2024

A negative feedback loop between small GTPase Rap1 and mammalian tumor suppressor homolog KrsB regulates cell-substrate adhesion in Dictyostelium

Cell adhesion to the substrate influences a variety of cell behaviors and its proper regulation is essential for migration, although details of the molecular pathways regulating cell adhesion during migration are lacking. Rap1 is a small GTPase that regulates adhesion in mammalian cells, as well as in Dictyostelium discoideum social amoeba, which is an established model for studying directed cell migration. In Dictyostelium, Rap1 controls adhesion via its effects on adhesion mediator talin and Ser/Thr kinase Phg2, which inhibits myosin II function. Kinase responsive to stress B (KrsB), a homolog of mammalian tumor suppressor MST1/2 and Drosophila Hippo, also regulates cell adhesion and migration, although the molecular mechanism of KrsB action is not understood. Since KrsB has been shown to interact with active Rap1 by mass spectroscopy, we investigated the genetic interaction between Rap1 and KrsB. Cells lacking KrsB have increased adhesion to the substrate, which leads to reduced movement. Expression of constitutively active Rap1 G12V increased cell spreading and adhesion even in the absence of KrsB, suggesting that Rap1 does not require KrsB to mediate cell adhesion. In contrast, dominant negative Rap1 S17N completely reversed the over-adhesive phenotype of KrsB-null cells and impaired KrsB phosphorylation, suggesting that KrsB activation and function in adhesion requires Rap1. Even though Rap1 did not require KrsB for its function in adhesion, KrsB negatively regulates Rap1 function as seen by increased cortical localization of Rap1 in KrsB-null cells. Consistent with this, chemoattractant-induced activation of downstream effectors of Rap1, TalB and Phg2, was increased in the absence of KrsB. Taken together, these findings suggest that Rap1 leads to activation of KrsB, which inhibits Rap1 and its downstream targets, shutting off adhesion. The existence of a negative feedback loop between Rap1 and KrsB may contribute to the dynamic regulation of cell adhesion that is necessary for rapid amoeboid-type migration.

cell biology↗

bioRxiv2024

Tumor-derived hypoxic small extracellular vesicles promote endothelial cell migration and tube formation via ALS2/Rab5/β-catenin signaling

Tumor hypoxia has been associated with cancer progression, angiogenesis, and metastasis via modifications in the release and cargo composition of extracellular vesicles secreted by tumor cells. Indeed, hypoxic extracellular vesicles are known to trigger a variety of angiogenic responses via different mechanisms. We recently showed that hypoxia promotes endosomal signaling in tumor cells via HIF-1-dependent induction of the guanine exchange factor ALS2, which activates Rab5, leading to downstream events involved in cell migration and invasion. Since Rab5-dependent signaling is required for endothelial cell migration and angiogenesis, we explored the possibility that hypoxia promotes the release of small extracellular vesicles containing ALS2, which in turn activate Rab5 in recipient endothelial cells leading to pro-angiogenic properties. In doing so, we found that hypoxia promoted ALS2 expression and incorporation as cargo within small extracellular vesicles, leading to subsequent transfer to recipient endothelial cells, promoting cell migration, tube formation and downstream Rab5 activation. Consequently, ALS2-containing small extracellular vesicles increased early endosome size and number in recipient endothelial cells, which was followed by subsequent sequestration of components of the {beta}-catenin destruction complex within endosomal compartments, leading to stabilization and nuclear localization of {beta}-catenin. These events converged in the expression of {beta}-catenin target genes involved in angiogenesis. Knockdown of ALS2 in donor-tumor cells, which precluded its incorporation into small extracellular vesicles, prevented Rab5-downstream events and endothelial cell responses, which depended on Rab5 activity and guanine exchange factor activity of ALS2. These findings indicate that vesicular ALS2, secreted in hypoxia, promotes endothelial cell events leading to angiogenesis. Finally, these events might explain how tumor angiogenesis proceeds in hypoxic conditions.

cell biology↗

bioRxiv2022

JBrowse 2: A modular genome browser with views of synteny and structural variation

We present JBrowse 2, a general-purpose genome annotation browser offering enhanced visualization of complex structural variation and evolutionary relationships. JBrowse 2 retains the core features of the open-source JavaScript genome browser JBrowse while adding new views for synteny, dotplots, breakpoints, gene fusions, and whole-genome overviews. The software readily allows users to share sessions, open multiple genomes or views, and navigate quickly between these views. It can be embedded in a web page, used as a standalone desktop application, or run from Jupyter notebooks or R sessions. Using a plugin framework, developers can create new data adapters, track types, and visualizations. These improvements are enabled by a ground-up redesign of the JBrowse architecture using modern web technology. We describe application functionality, use cases, performance benchmarks, and implementation notes for web administrators and developers.

bioinformatics↗

bioRxiv2019

How neurons move during action potentials

Neurons undergo nanometer-scale deformations during action potentials, and the underlying mechanism has been actively debated for decades. Previous observations were limited to a single spot or the cell boundary, while movement across the entire neuron during the action potential remained unclear.\n\nWe report full-field imaging of cellular deformations accompanying the action potential in mammalian neuron somas (-1.8nm~1.3nm) and neurites (-0.7nm~0.9nm), using fast quantitative phase imaging with a temporal resolution of 0.1ms and an optical pathlength sensitivity of <4pm per pixel. Spike-triggered average, synchronized to electrical recording, demonstrates that the time course of the optical phase changes matches the dynamics of the electrical signal, with the optical signal revealing the intracellular potential rather than its time derivative detected via extracellular electrodes. Using 3D cellular morphology extracted via confocal microscopy, we demonstrate that the voltage-dependent changes in the membrane tension induced by ionic repulsion can explain the magnitude, time course and spatial features of the phase imaging. Our full-field observations of the spike-induced deformations in mammalian neurons opens the door to non-invasive label-free imaging of neural signaling.

neuroscience↗