scholarly journals Worrying drives cell migration in mechanically unrestrained environments

2020 ◽  
Author(s):  
Erik S. Welf ◽  
Meghan K. Driscoll ◽  
Etai Sapoznik ◽  
Vasanth S. Murali ◽  
Andrew Weems ◽  
...  
Keyword(s):  
Extracellular Fluid ◽  
Alternative Mechanism ◽  
Dynamic Membrane ◽  
Membrane Blebs ◽  
Cell Front ◽  
3D Collagen ◽  
Migratory Cells ◽  
Pericellular Proteolysis ◽  
Extracellular Proteolysis

AbstractMigratory cells employ numerous strategies to navigate the very diverse 3D microenvironments found in vivo. These strategies are subdivided into those that create space by pericellular proteolysis of extracellular matrix (ECM) proteins and those that navigate existing spaces. We find that cells can employ an alternative mechanism by digging tunnels through 3D collagen networks without extracellular proteolysis. This is accomplished by persistent polarization of large dynamic membrane blebs at the closed end of the tunnel that repeatedly agitate the collagen, a process we termed mechanical worrying. We find that this agitation promotes breakage and internalization of collagen at the cell front along with extracellular fluid in a macropinocytosis-driven manner. Membrane blebs are short-lived relative to the timescale of migration, and thus their polarization is critical for persistent ablation of the ECM. We find that sustained interactions between the collagen at the cell front and small but persistent cortical adhesions induce PI-3 Kinase (PI3K) signaling that drives polarized bleb enlargement via the Rac1 – Arp2/3 pathway. This defines a mechanism for the reinforcement of bleb expansion against load, which enables precise ablation of mechanically unrestrained environments, such as those encountered in very compliant tissue.

Mimicking osteocytes in vivo using 3D collagen gels: development of a novel tool to study osteocyte biology

2013 ◽  
pp. 1-1
Author(s):  
Nicole Scully ◽  
Sam L Evans ◽  
Deborah J Mason ◽  
Bronwen A J Evans
Keyword(s):  
Collagen Gels ◽  
3D Collagen

scholarly journals RNA-seq Characterization of Melanoma Phenotype Switch in 3D Collagen after p38 MAPK Inhibitor Treatment

Biomolecules ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 449
Author(s):  
Vladimír Čermák ◽  
Aneta Škarková ◽  
Ladislav Merta ◽  
Veronika Kolomazníková ◽  
Veronika Palušová ◽  
...  
Keyword(s):  
P38 Mapk ◽  
Rna Seq ◽  
Differentiation Markers ◽  
Illumina Hiseq ◽  
Invasive Phenotype ◽  
Mesenchymal Transition ◽  
Phenotype Switch ◽  
3D Collagen ◽  
Phenotype Plasticity

Melanoma phenotype plasticity underlies tumour dissemination and resistance to therapy, yet its regulation is incompletely understood. In vivo switching between a more differentiated, proliferative phenotype and a dedifferentiated, invasive phenotype is directed by the tumour microenvironment. We found that treatment of partially dedifferentiated, invasive A375M2 cells with two structurally unrelated p38 MAPK inhibitors, SB2021920 and BIRB796, induces a phenotype switch in 3D collagen, as documented by increased expression of melanocyte differentiation markers and a loss of invasive phenotype markers. The phenotype is accompanied by morphological change corresponding to amoeboid–mesenchymal transition. We performed RNA sequencing with an Illumina HiSeq platform to fully characterise transcriptome changes underlying the switch. Gene expression results obtained with RNA-seq were validated by comparing them with RT-qPCR. Transcriptomic data generated in the study will extend the present understanding of phenotype plasticity in melanoma and its contribution to invasion and metastasis.

scholarly journals LanCL1 promotes motor neuron survival and extends the lifespan of amyotrophic lateral sclerosis mice

2019 ◽  
Vol 27 (4) ◽  
pp. 1369-1382 ◽  
Author(s):  
Honglin Tan ◽  
Mina Chen ◽  
Dejiang Pang ◽  
Xiaoqiang Xia ◽  
Chongyangzi Du ◽  
...  
Keyword(s):  
Amyotrophic Lateral Sclerosis ◽  
Motor Neuron ◽  
Motor Neurons ◽  
Neuronal Survival ◽  
Disease Onset ◽  
Alternative Mechanism ◽  
Specific Expression ◽  
Motor Neuron Survival ◽  
Lateral Sclerosis

Abstract Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive loss of motor neurons. Improving neuronal survival in ALS remains a significant challenge. Previously, we identified Lanthionine synthetase C-like protein 1 (LanCL1) as a neuronal antioxidant defense gene, the genetic deletion of which causes apoptotic neurodegeneration in the brain. Here, we report in vivo data using the transgenic SOD1G93A mouse model of ALS indicating that CNS-specific expression of LanCL1 transgene extends lifespan, delays disease onset, decelerates symptomatic progression, and improves motor performance of SOD1G93A mice. Conversely, CNS-specific deletion of LanCL1 leads to neurodegenerative phenotypes, including motor neuron loss, neuroinflammation, and oxidative damage. Analysis reveals that LanCL1 is a positive regulator of AKT activity, and LanCL1 overexpression restores the impaired AKT activity in ALS model mice. These findings indicate that LanCL1 regulates neuronal survival through an alternative mechanism, and suggest a new therapeutic target in ALS.

scholarly journals A nucleosome-positioning sequence is required for GCN4 to activate transcription in the absence of a TATA element.

1990 ◽  
Vol 10 (8) ◽  
pp. 4256-4265 ◽  
Author(s):  
C J Brandl ◽  
K Struhl
Keyword(s):  
Binding Site ◽  
Transcriptional Activation ◽  
Nucleosome Positioning ◽  
Alternative Mechanism ◽  
Tata Element ◽  
Binding Factor ◽  
Positioning Analysis ◽  
Binding Sequence

In the gal-his3 hybrid promoter his3-GG1, the yeast upstream activator protein GCN4 stimulates transcription when bound at the position normally occupied by the TATA element. This TATA-independent activation by GCN4 requires two additional elements in the gal enhancer region that are distinct from those involved in normal galactose induction. Both additional elements appear to be functionally distinct from a classical TATA element because they cannot be replaced by the TFIID-binding sequence TATAAA. One of these elements, termed Q, is essential for GCN4-activated transcription and contains the sequence GTCAC CCG, which overlaps (but is distinct from) a GAL4 binding site. Surprisingly, relatively small increases in the distance between Q and the GCN4 binding site significantly reduce the level of transcription. The Q element specifically interacts with a yeast protein (Q-binding protein [QBP]) that may be equivalent to Y, a protein that binds at a sequence that forms a constraint to nucleosome positioning. Analysis of various deletion mutants indicates that the sequence requirements for binding by QBP in vitro are indistinguishable from those necessary for Q activity in vivo, strongly suggesting that QBP is required for the function of this TATA-independent promoter. These results support the view that transcriptional activation can occur by an alternative mechanism in which the TATA-binding factor TFIID either is not required or is not directly bound to DNA. In addition, they suggest a potential role of nucleosome positioning for the activity of a promoter.

scholarly journals Increased extracellular fluid is associated with white matter fiber degeneration in CADASIL: in vivo evidence from diffusion magnetic resonance imaging

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Xinfeng Yu ◽  
Xinzhen Yin ◽  
Hui Hong ◽  
Shuyue Wang ◽  
Yeerfan Jiaerken ◽  
...  
Keyword(s):  
White Matter ◽  
Diffusion Tensor ◽  
Small Vessel Disease ◽  
Extracellular Fluid ◽  
Free Water ◽  
Inverse Correlation ◽  
Brain Regions ◽  
Fiber Density ◽  
Four Levels

Abstract Background White matter hyperintensities (WMHs) are one of the hallmarks of cerebral small vessel disease (CSVD), but the pathological mechanisms underlying WMHs remain unclear. Recent studies suggest that extracellular fluid (ECF) is increased in brain regions with WMHs. It has been hypothesized that ECF accumulation may have detrimental effects on white matter microstructure. To test this hypothesis, we used cerebral autosomal-dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL) as a unique CSVD model to investigate the relationships between ECF and fiber microstructural changes in WMHs. Methods Thirty-eight CADASIL patients underwent 3.0 T MRI with multi-model sequences. Parameters of free water (FW) and apparent fiber density (AFD) obtained from diffusion-weighted imaging (b = 0 and 1000 s/mm2) were respectively used to quantify the ECF and fiber density. WMHs were split into four subregions with four levels of FW using quartiles (FWq1 to FWq4) for each participant. We analyzed the relationships between FW and AFD in each subregion of WMHs. Additionally, we tested whether FW of WMHs were associated with other accompanied CSVD imaging markers including lacunes and microbleeds. Results We found an inverse correlation between FW and AFD in WMHs. Subregions of WMHs with high-level of FW (FWq3 and FWq4) were accompanied with decreased AFD and with changes in FW-corrected diffusion tensor imaging parameters. Furthermore, FW was also independently associated with lacunes and microbleeds. Conclusions Our study demonstrated that increased ECF was associated with WM degeneration and the occurrence of lacunes and microbleeds, providing important new insights into the role of ECF in CADASIL pathology. Improving ECF drainage might become a therapeutic strategy in future.

Time course of exchanges between red cells and extracellular fluid during CO2 uptake

1975 ◽  
Vol 38 (4) ◽  
pp. 710-718 ◽  
Author(s):  
R. E. Forster ◽  
E. D. Crandall
Keyword(s):  
Carbonic Anhydrase ◽  
Time Course ◽  
Extracellular Fluid ◽  
Extracellular Ph ◽  
Co2 Uptake ◽  
Sudden Increase ◽  
Red Cell ◽  
Ph Change ◽  
Red Cell Membrane

A stopped-flow rapid-reaction apparatus was used to follow the time course of extracellular pH in a human red cell suspension following a sudden increase in PCO2. The extracellular pH change was slow (t1/2 similar to 3.5 s) considering the presence of carbonic anhydrase in the cells. When carbonic anhydrase was added to the extracellular fluid, the half-time was reduced to less than 20 ms. The explanation for these phenomena is that the equilibration of H+ across the red cell membrane is rate-limited by the uncatalyzed reaction CO2 plus H2O formed from H2CO3 outside the cells. A theoretical model was developed which successfully reproduced the experimental results. When the model was used to simulate CO2 exchange in vivo, it was determined that blood PCO2 and pH require long times (greater than 50 s) to approach equilibrium between cells and plasma after leaving an exchange capillary. We conclude that cell-plasma equilibrium may never be reached in vivo, and that in vitro measurements of these quantities may not represent their true values at the site of sampling.

A possible alternative mechanism of kinin generation in vivo by cathepsin L

2005 ◽  
Vol 386 (7) ◽  
pp. 699-704 ◽  
Author(s):  
Luciano Puzer ◽  
Juliana Vercesi ◽  
Marcio F.M. Alves ◽  
Nilana M.T. Barros ◽  
Mariana S. Araujo ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Enzyme Inhibitor ◽  
Alternative Pathway ◽  
Cathepsin L ◽  
Specific Inhibitor ◽  
Cysteine Proteases ◽  
Hypotensive Effect ◽  
Alternative Mechanism

Abstract We investigated the ability of cathepsin L to induce a hypotensive effect after intravenous injection in rats and correlated this decrease in blood pressure with kinin generation. Simultaneously with blood pressure decrease, we detected plasma kininogen depletion in the treated rats. The effect observed in vivo was abolished by pre-incubation of cathepsin L with the cysteine peptidase-specific inhibitor E-64 (1 μM) or by previous administration of the bradykinin B2 receptor antagonist JE049 (4 mg/kg). A potentiation of the hypotensive effect caused by cathepsin L was observed by previous administration of the angiotensin I-converting enzyme inhibitor captopril (5 mg/kg). In vitro studies indicated that cathepsin L excised bradykinin from the synthetic fluorogenic peptide Abz-MTSVIRRPPGFSPFRAPRV-NH2, based on the Met375–Val393 sequence of rat kininogen (Abz=o-aminobenzoic acid). In conclusion, our data indicate that in vivo cathepsin L releases a kinin-related peptide, and in vitro experiments suggest that the kinin generated is bradykinin. Although it is well known that cysteine proteases are strongly inhibited by kininogen, cathepsin L could represent an alternative pathway for kinin production in pathological processes.

Extracellular Fluid Volume Changes in Carcinus Maenas during Acclimation to Low and High Environmental Salinities

1982 ◽  
Vol 99 (1) ◽  
pp. 161-173
Author(s):  
R. R. HARRIS ◽  
M. B. ANDREWS
Keyword(s):  
Sea Water ◽  
Carcinus Maenas ◽  
Extracellular Fluid ◽  
Blood Sampling ◽  
Extracellular Fluid Volume ◽  
Clearance Rates ◽  
Volume Changes ◽  
Marker Distribution ◽  
Water Contents

Changes in extracellular fluid (ECF) volume of Carcinus maenas (L.) were studied in vivo during acclimation to low and high environmental salinities. Initial investigations showed that there was a rapid equilibration into this compartment of the ECF markers used ([3H]inulin and [14C]hydroxymethyl inulin). Earlier reports of a relatively slow marker distribution, indicated from clearance curves, can be explained by high clearance rates occurring when frequent blood sampling was carried out. After transfer of the crabs to media hyposmotic to the haemolymph, ECF volumes decreased transiently to 74.8% of the initial volume, but within 40 h in 26% sea water original volumes were restored. Calculation of intracellular water contents suggests that a volume limitation phase precedes the regulatory return to the original volume. In hyperosmotic media, the ECF volumes increased significantly (to a maximum of 143%) but, in contrast to the response in hyposmotic conditions, showed only a partial return to the original volumes.

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