Biology subjects

Hall, E. A.

Publications and source records attributed to Hall, E. A..

6 recordsLinked to original sources

bioRxiv2024

Integrative cardiovascular dose-response to graded lower body negative pressure

BackgroundLower body negative pressure (LBNP) has been posited as a potential spaceflight countermeasure to counteract the physiological deconditioning related to fluid shifts in micro-gravity. However, open questions remain as to the magnitude of LBNP that should be applied. We systematically characterized the cardiovascular effects of LBNP and quantified the effect size of varied LBNP doses across different parts of the cardiovascular system. MethodsTwenty-four subjects (12M, 12F) were exposed to graded LBNP from 0 mmHg to -50 mmHg in 10 mmHg increments, both in supine (0{degrees}) and 15{degrees} head-down tilt postures. We measured the steady-state response in a large range of variables, including those related to the systemic circulation, cardiovascular control, and hemodynamics of the eyes and neck. ResultsBuilding on the experimental data, dose-response curves were constructed using a Bayesian multivariate hierarchical modeling framework to quantify the effect size of every variable considered when subjected to LBNP. The methodology allows direct comparison of the variables and the underlying structural relationships between them. Further, we demonstrated the potential for LBNP to reduce jugular venous flow stagnation, which is considered one of the major health risks during human spaceflight. ConclusionsThe Dose-response curves and effect sizes generated from this research effort establish the most comprehensive framework available to date that characterizes physiological responses to LBNP. These results directly inform the development of countermeasures to mitigate the negative effects of spaceflight, including cardiovascular deconditioning, spaceflight-associated neuro-ocular syndrome, and venous thromboembolism events. Key Points SummaryO_LILower body negative pressure (LBNP) has been posited as a potential countermeasure for multiple risks associated with spaceflight, including cardiovascular deconditioning, spaceflight-associated neuro-ocular syndrome, and venous thromboembolism events. However, the specific LBNP dose needed to mitigate these risks is still unknown. C_LIO_LIWe constructed the LBNP dose-response curves in supine and 15{degrees} head-down-tilt positions to quantify the acute response of a large variety of hemodynamics, autonomic, ocular, and neck variables across a range of LBNP levels. C_LIO_LIWe also used a Bayesian multivariate modeling framework to identify significant relationships between variables and to compare their effect sizes under different levels of LBNP. C_LIO_LIIn addition, results indicate that LBNP is a promising countermeasure to reduce jugular venous flow stagnation occurring during microgravity exposure. C_LIO_LIThis study constitutes the most comprehensive analysis of cardiovascular hemodynamics, autonomic, and cephalad response to LBNP to date. This framework informs the development of countermeasures to mitigate the detrimental effects of spaceflight. C_LI

physiology↗

bioRxiv2024

Intracellular pH dynamics respond to microenvironment stiffening and mediate vasculogenic mimicry through β-catenin

Dysregulated intracellular pH (pHi) dynamics and an altered tumor microenvironment have emerged as drivers of cancer cell phenotypes. However, the molecular integration between the physical properties of the microenvironment and dynamic intracellular signaling responses remains unclear. Here, we identify a mechanistic link between ECM stiffness and pHi dynamics in driving vasculogenic mimicry (VM), an aggressive cancer phenotype associated with poor prognosis. We performed single-cell imaging of pHi in lung and breast metastatic cell lines cultured on tunable-stiffness hydrogel systems. We used two tunable-stiffness hydrogel systems to independently model stiffness induced by increased protein secretion (Matrigel) and increased protein crosslinking (Hyaluronic acid gels). We show that increased ECM stiffness lowers single-cell pHi in both lung and breast metastatic cell lines. We also observed that stiff ECM promotes a distinct morphological phenotype called vasculogenic mimicry (VM). Importantly, we show that low pHi is a necessary mediator of VM, as raising pHi on stiff ECM reduces VM phenotypes. We also find that lowering pHi on soft ECM was sufficient to induce VM in the absence of extracellular stiffening. We characterized {beta}-catenin as a pH-dependent molecular mediator of VM, where stiffness-driven increases in {beta}-catenin abundance can be overridden by high pHi, which destabilizes {beta}-catenin to reduce VM on stiff ECM. In contrast, the transcription factor FOXC2 is activated by ECM stiffness but is insensitive to pHi, and its activity alone is insufficient to maintain VM at high pHi when {beta}-catenin is lost. We uncover a novel mechanotransduction axis in which ECM stiffness regulates intracellular pH to drive {beta}-catenin-induced VM. We also show pHi dynamics can override mechanosensitive cell responses to the extracellular microenvironment. Thus, our work positions pHi as an integrator of mechanotransduction in cancer, suggesting a new framework for therapeutically targeting pHi in cancer and perhaps in other diseases driven by ECM remodeling.

cell biology↗

bioRxiv2022

Centriolar satellites expedite mother centriole remodeling to promote ciliogenesis.

Centrosomes are orbited by centriolar satellites, dynamic multiprotein assemblies nucleated by PCM1. To study the requirement for centriolar satellites, we generated mice lacking PCM1. Pcm1-/- mice display partially penetrant perinatal lethality with survivors exhibiting hydrocephalus, oligospermia and cerebellar hypoplasia, as well as variable expressivity of other ciliopathy features including cystic kidneys. Pcm1-/- multiciliated ependymal cells and PCM1-/- retinal pigmented epithelial 1 (RPE1) cells showed reduced ciliogenesis. PCM1-/- RPE1 cells displayed reduced docking of the mother centriole to the ciliary vesicle and removal of CP110 and CEP97 from the distal mother centriole, indicating compromized early ciliogenesis. We show these molecular cascades are maintained in vivo, and we suggest that the cellular threshold to trigger ciliogenesis varies between cell types. We propose that PCM1 and centriolar satellites facilitate efficient trafficking of proteins to and from centrioles, inducing the departure of CP110 and CEP97 to initiate ciliogenesis.

cell biology↗

bioRxiv2020

A WDR35/IFT121-dependent coatomer transports ciliary membrane proteins from the Golgi to the cilia

Intraflagellar transport (IFT) is a highly conserved mechanism for motor-driven transport of cargo within cilia, but how this cargo is selectively transported to cilia and across the diffusion barrier is unclear. WDR35/IFT121 is a component of the IFT-A complex best known for its role in ciliary retrograde transport. In the absence of WDR35, small mutant cilia form but fail to enrich in diverse classes of ciliary membrane proteins. In Wdr35 mouse mutants, the IFT-A peripheral components are degraded and core components accumulate at the transition zone. We reveal deep sequence homology and structural similarity of WDR35 and other IFT-As to the coatomer COPI proteins a and {beta}', and demonstrate an accumulation of coat-less vesicles which fail to fuse with Wdr35 mutant cilia. Our data provides the first in situ evidence of a novel coatomer function for WDR35 likely with other IFT-A proteins in delivering ciliary membrane cargo from the Golgi necessary for cilia elongation.

cell biology↗

bioRxiv2019

Nucleocytoplasmic Proteomic Analysis Uncovers ETF1 and Nonsense Mediated Decay as Modifiers of ALS C9orf72 Toxicity

The most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) is a hexanucleotide repeat expansion in C9orf72 (C9-HRE). While RNA and dipeptide repeats produced by the C9-HRE disrupt nucleocytoplasmic transport, the proteins that become redistributed remain unknown. Here, we utilized subcellular fractionation coupled with tandem mass spectrometry and identified 126 proteins, enriched for protein translation and RNA metabolism pathways, which collectively drive a shift towards a more cytosolic proteome in C9-HRE cells. Amongst these was eRF1, which regulates translation termination and nonsense-mediated decay (NMD). eRF1 accumulates within elaborate nuclear envelope invaginations in patient iPSC-neurons and postmortem tissue and mediates a protective shift from protein translation to NMD-dependent mRNA degradation. Overexpression of eRF1 and the NMD-driver UPF1 ameliorate C9-HRE toxicity in vivo. Our findings provide a resource for proteome-wide nucleocytoplasmic alterations across neurodegeneration-associated repeat expansion mutations and highlight eRF1 and NMD as therapeutic targets in C9orf72-associated ALS/FTD.

neuroscience↗

bioRxiv2019

CNTNAP2 ectodomain, detected in neuronal and CSF sheddomes, modulates Ca2+ dynamics and network synchrony

SUMMARYWhile many neuronal membrane-anchored proteins undergo proteolytic cleavage, little is known about the biological significance of neuronal ectodomain shedding. Using mass spectrometry (MS)-based proteomics, we showed that the neuronal sheddome mirrors human cerebrospinal fluid (hCSF). Among shed synaptic proteins in hCSF was the ectodomain of CNTNAP2 (CNTNAP2-ecto), a risk factor for neurodevelopmental disorders (NDD). Using structured-illumination microscopy (SIM), we mapped the spatial organization of neuronal CNTNAP2-ecto shedding. Using affinity chromatography followed by MS, we identified the ATP2B/PMCA Ca2+ extrusion pumps as novel CNTNAP2-ecto binding partners. CNTNAP2-ecto coimmunoprecipitates with PMCA2, a known autism risk factor, and enhances its activity, thereby modulating neuronal Ca2+ levels. Finally, we showed that CNTNAP2-ecto regulates neuronal network synchrony in primary cultures and brain slices. These data provide new insights into the biology of synaptic ectodomain shedding and reveal a novel mechanism of regulation of Ca2+ homeostasis and neuronal network synchrony.

neuroscience↗