scholarly journals Intercellular alignment of apical-basal polarity coordinates tissue homeostasis and growth

2021 ◽  
Author(s):  
Jinghua Gui ◽  
Yunxian Huang ◽  
Satu-Marja Myllymäki ◽  
Marja Mikkola ◽  
Osamu Shimmi
Keyword(s):  
Imaginal Disc ◽  
Tissue Level ◽  
Septate Junction ◽  
Dependent Manner ◽  
Wild Type ◽  
Apicobasal Polarity ◽  
The Status ◽  
Physical Interactions ◽  
Mutant Cells ◽  
Intercellular Network

AbstractMaintaining apicobasal polarity (ABP) is crucial for epithelial integrity and homeostasis during tissue development. Although recent studies have greatly advanced our understanding of intracellular mechanisms underlying ABP establishment, it remains largely unknown how the ABP is regulated at the tissue level. Here, we address intercellular mechanisms coordinating ABP using the Drosophila wing imaginal disc. By studying Scribble, a key ABP determinant, we show that ABP is regulated through intercellular alignment, which takes place either progressively or regressively in a context-dependent manner. Cells expressing wild type scribble progressively restore ABP in scribble hypomorphic mutant cells. In contrast, cells with conditional scribble knockdown instigate the regressive loss of polarity in abutting wild type cells. Our data reveal that genetic and physical interactions between Scribble, Septate junction complex and α-Catenin appear to be key for sustaining intercellular network of ABP. Taken together, our findings indicate that the intercellular relay of the status of ABP contributes to the robustness of polarity across the tissue.

scholarly journals Role for Gcs1p in Regulation of Arl1p atTrans-Golgi Compartments

2005 ◽  
Vol 16 (9) ◽  
pp. 4024-4033 ◽  
Author(s):  
Ya-Wen Liu ◽  
Chun-Fang Huang ◽  
Kai-Bin Huang ◽  
Fang-Jen S. Lee
Keyword(s):  
Dynamic Equilibrium ◽  
Vesicular Trafficking ◽  
Dependent Manner ◽  
Wild Type ◽  
Gtpase Activating Protein ◽  
Critical Components ◽  
Mutant Cells ◽  
Hydrolysis Of ◽  
Adp Ribosylation Factor

ADP-ribosylation factor (ARF) and ARF-like (ARL) proteins are members of the ARF family, which are critical components of several different vesicular trafficking pathways. ARFs have little or no detectable GTPase activity without the assistance of a GTPase-activating protein (GAP). Here, we demonstrate that yeast Gcs1p exhibits GAP activity toward Arl1p and Arf1p in vitro, and Arl1p can interact with Gcs1p in a GTP-dependent manner. Arl1p was observed both on trans-Golgi and in cytosol and was recruited from cytosol to membranes in a GTP-dependent manner. In gcs1 mutant cells, the fraction of Arl1p in cytosol relative to trans-Golgi was less than it was in wild-type cells. Increasing Gcs1p levels returned the distribution toward that of wild-type cells. Both Arl1p and Gcs1p influenced the distribution of Imh1p, an Arl1p effector. Our data are consistent with the conclusion that Arl1p moves in a dynamic equilibrium between trans-Golgi and cytosol, and the release of Arl1p from membranes in cells requires the hydrolysis of bound GTP, which is accelerated by Gcs1p.

scholarly journals The H3K27me3 Demethylase dUTX Is a Suppressor of Notch- and Rb-Dependent Tumors in Drosophila

2010 ◽  
Vol 30 (10) ◽  
pp. 2485-2497 ◽  
Author(s):  
Hans-Martin Herz ◽  
Laurence D. Madden ◽  
Zhihong Chen ◽  
Clare Bolduc ◽  
Eugene Buff ◽  
...  
Keyword(s):  
Drosophila Melanogaster ◽  
Histone H3 ◽  
Epigenetic Mark ◽  
Dependent Manner ◽  
Wild Type ◽  
Independent Manner ◽  
Jmjc Domain ◽  
Mutant Cells ◽  
Excessive Activation

ABSTRACT Trimethylated lysine 27 of histone H3 (H3K27me3) is an epigenetic mark for gene silencing and can be demethylated by the JmjC domain of UTX. Excessive H3K27me3 levels can cause tumorigenesis, but little is known about the mechanisms leading to those cancers. Mutants of the Drosophila H3K27me3 demethylase dUTX display some characteristics of Trithorax group mutants and have increased H3K27me3 levels in vivo. Surprisingly, dUTX mutations also affect H3K4me1 levels in a JmjC-independent manner. We show that a disruption of the JmjC domain of dUTX results in a growth advantage for mutant cells over adjacent wild-type tissue due to increased proliferation. The growth advantage of dUTX mutant tissue is caused, at least in part, by increased Notch activity, demonstrating that dUTX is a Notch antagonist. Furthermore, the inactivation of Retinoblastoma (Rbf in Drosophila) contributes to the growth advantage of dUTX mutant tissue. The excessive activation of Notch in dUTX mutant cells leads to tumor-like growth in an Rbf-dependent manner. In summary, these data suggest that dUTX is a suppressor of Notch- and Rbf-dependent tumors in Drosophila melanogaster and may provide a model for UTX-dependent tumorigenesis in humans.

scholarly journals Peroxisomal Membrane Proteins Insert into the Endoplasmic Reticulum

2010 ◽  
Vol 21 (12) ◽  
pp. 2057-2065 ◽  
Author(s):  
Adabella van der Zand ◽  
Ineke Braakman ◽  
Henk F. Tabak
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Proteins ◽  
Functional Role ◽  
Protein Import ◽  
Mutant Gene ◽  
Dependent Manner ◽  
Wild Type ◽  
Peroxisomal Membrane ◽  
Trafficking Pathway ◽  
Mutant Cells

We show that a comprehensive set of 16 peroxisomal membrane proteins (PMPs) encompassing all types of membrane topologies first target to the endoplasmic reticulum (ER) in Saccharomyces cerevisiae. These PMPs insert into the ER membrane via the protein import complexes Sec61p and Get3p (for tail-anchored proteins). This trafficking pathway is representative for multiplying wild-type cells in which the peroxisome population needs to be maintained, as well as for mutant cells lacking peroxisomes in which new peroxisomes form after complementation with the wild-type version of the mutant gene. PMPs leave the ER in a Pex3p-Pex19p–dependent manner to end up in metabolically active peroxisomes. These results further extend the new concept that peroxisomes derive their basic framework (membrane and membrane proteins) from the ER and imply a new functional role for Pex3p and Pex19p.

Ultrastructure and Morphology of the Neurospora Crassa Cell Wall Mutants, Slime And Slime X, Using Tem and Sem

1976 ◽  
Vol 34 ◽  
pp. 54-55
Author(s):  
Karen S. Howard ◽  
H. D. Braymer ◽  
M. D. Socolofsky ◽  
S. A. Milligan
Keyword(s):  
Cell Wall ◽  
Neurospora Crassa ◽  
Wild Type ◽  
Morphological Comparison ◽  
Small Areas ◽  
Solid Media ◽  
Thin Sectioning ◽  
X Cells ◽  
Mutant Cells ◽  
Isolated Cell

The recently isolated cell wall mutant slime X of Neurospora crassa was prepared for ultrastructural and morphological comparison with the cell wall mutant slime. The purpose of this article is to discuss the methods of preparation for TEM and SEM observations, as well as to make a preliminary comparison of the two mutants.TEM: Cells of the slime mutant were prepared for thin sectioning by the method of Bigger, et al. Slime X cells were prepared in the same manner with the following two exceptions: the cells were embedded in 3% agar prior to fixation and the buffered solutions contained 5% sucrose throughout the procedure.SEM: Two methods were used to prepare mutant and wild type Neurospora for the SEM. First, single colonies of mutant cells and small areas of wild type hyphae were cut from solid media and fixed with OSO4 vapors similar to the procedure used by Harris, et al. with one alteration. The cell-containing agar blocks were dehydrated by immersion in 2,2-dimethoxypropane (DMP).

scholarly journals Annexin A6 modulates TBC1D15/Rab7/StARD3 axis to control endosomal cholesterol export in NPC1 cells

2019 ◽  
Vol 77 (14) ◽  
pp. 2839-2857 ◽  
Author(s):  
Elsa Meneses-Salas ◽  
Ana García-Melero ◽  
Kristiina Kanerva ◽  
Patricia Blanco-Muñoz ◽  
Frederic Morales-Paytuvi ◽  
...  
Keyword(s):  
Late Endosome ◽  
Dependent Manner ◽  
Lipid Transfer ◽  
Cholesterol Accumulation ◽  
Membrane Contact Sites ◽  
Late Endosomes ◽  
Membrane Contact ◽  
Domain 3 ◽  
Niemann Pick ◽  
Mutant Cells

Abstract Cholesterol accumulation in late endosomes is a prevailing phenotype of Niemann-Pick type C1 (NPC1) mutant cells. Likewise, annexin A6 (AnxA6) overexpression induces a phenotype reminiscent of NPC1 mutant cells. Here, we demonstrate that this cellular cholesterol imbalance is due to AnxA6 promoting Rab7 inactivation via TBC1D15, a Rab7-GAP. In NPC1 mutant cells, AnxA6 depletion and eventual Rab7 activation was associated with peripheral distribution and increased mobility of late endosomes. This was accompanied by an enhanced lipid accumulation in lipid droplets in an acyl-CoA:cholesterol acyltransferase (ACAT)-dependent manner. Moreover, in AnxA6-deficient NPC1 mutant cells, Rab7-mediated rescue of late endosome-cholesterol export required the StAR-related lipid transfer domain-3 (StARD3) protein. Electron microscopy revealed a significant increase of membrane contact sites (MCS) between late endosomes and ER in NPC1 mutant cells lacking AnxA6, suggesting late endosome-cholesterol transfer to the ER via Rab7 and StARD3-dependent MCS formation. This study identifies AnxA6 as a novel gatekeeper that controls cellular distribution of late endosome-cholesterol via regulation of a Rab7-GAP and MCS formation.

scholarly journals EPHA2-dependent outcompetition of KRASG12D mutant cells by wild-type neighbors in the adult pancreas

2021 ◽  
Author(s):  
William Hill ◽  
Andreas Zaragkoulias ◽  
Beatriz Salvador-Barbero ◽  
Geraint J. Parfitt ◽  
Markella Alatsatianos ◽  
...  
Keyword(s):  
Wild Type ◽  
Mutant Cells

scholarly journals Colony spreading of the gliding bacterium Flavobacterium johnsoniae in the absence of the motility adhesin SprB

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Keiko Sato ◽  
Masami Naya ◽  
Yuri Hatano ◽  
Yoshio Kondo ◽  
Mari Sato ◽  
...  
Keyword(s):  
Soft Agar ◽  
Gliding Motility ◽  
Wild Type ◽  
Initial Cell ◽  
Flavobacterium Johnsoniae ◽  
Seeking Behavior ◽  
Colony Spreading ◽  
Gliding Bacterium ◽  
Mutant Cells ◽  
Scanning Electron

AbstractColony spreading of Flavobacterium johnsoniae is shown to include gliding motility using the cell surface adhesin SprB, and is drastically affected by agar and glucose concentrations. Wild-type (WT) and ΔsprB mutant cells formed nonspreading colonies on soft agar, but spreading dendritic colonies on soft agar containing glucose. In the presence of glucose, an initial cell growth-dependent phase was followed by a secondary SprB-independent, gliding motility-dependent phase. The branching pattern of a ΔsprB colony was less complex than the pattern formed by the WT. Mesoscopic and microstructural information was obtained by atmospheric scanning electron microscopy (ASEM) and transmission EM, respectively. In the growth-dependent phase of WT colonies, dendritic tips spread rapidly by the movement of individual cells. In the following SprB-independent phase, leading tips were extended outwards by the movement of dynamic windmill-like rolling centers, and the lipoproteins were expressed more abundantly. Dark spots in WT cells during the growth-dependent spreading phase were not observed in the SprB-independent phase. Various mutations showed that the lipoproteins and the motility machinery were necessary for SprB-independent spreading. Overall, SprB-independent colony spreading is influenced by the lipoproteins, some of which are involved in the gliding machinery, and medium conditions, which together determine the nutrient-seeking behavior.

scholarly journals Knockout of Putative Tumor Suppressor Aldh1l1 in Mice Reprograms Metabolism to Accelerate Growth of Tumors in a Diethylnitrosamine (DEN) Model of Liver Carcinogenesis

Cancers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 3219
Author(s):  
Natalia I. Krupenko ◽  
Jaspreet Sharma ◽  
Halle M. Fogle ◽  
Peter Pediaditakis ◽  
Kyle C. Strickland ◽  
...  
Keyword(s):  
Tumor Growth ◽  
Chemical Carcinogenesis ◽  
Dependent Manner ◽  
Wild Type ◽  
Liver Carcinogenesis ◽  
Wild Type Littermate ◽  
Tumor Multiplicity ◽  
Accelerate Growth ◽  
Putative Tumor Suppressor ◽  
Formyltetrahydrofolate Dehydrogenase

Cytosolic 10-formyltetrahydrofolate dehydrogenase (ALDH1L1) is commonly downregulated in human cancers through promoter methylation. We proposed that ALDH1L1 loss promotes malignant tumor growth. Here, we investigated the effect of the Aldh1l1 mouse knockout (Aldh1l1−/−) on hepatocellular carcinoma using a chemical carcinogenesis model. Fifteen-day-old male Aldh1l1 knockout mice and their wild-type littermate controls (Aldh1l1+/+) were injected intraperitoneally with 20 μg/g body weight of DEN (diethylnitrosamine). Mice were sacrificed 10, 20, 28, and 36 weeks post-DEN injection, and livers were examined for tumor multiplicity and size. We observed that while tumor multiplicity did not differ between Aldh1l1−/− and Aldh1l1+/+ animals, larger tumors grew in Aldh1l1−/− compared to Aldh1l1+/+ mice at 28 and 36 weeks. Profound differences between Aldh1l1−/− and Aldh1l1+/+ mice in the expression of inflammation-related genes were seen at 10 and 20 weeks. Of note, large tumors from wild-type mice showed a strong decrease of ALDH1L1 protein at 36 weeks. Metabolomic analysis of liver tissues at 20 weeks showed stronger differences in Aldh1l1+/+ versus Aldh1l1−/− metabotypes than at 10 weeks, which underscores metabolic pathways that respond to DEN in an ALDH1L1-dependent manner. Our study indicates that Aldh1l1 knockout promoted liver tumor growth without affecting tumor initiation or multiplicity.

scholarly journals Targeting the DNA replication stress phenotype of KRAS mutant cancer cells

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tara Al Zubaidi ◽  
O. H. Fiete Gehrisch ◽  
Marie-Michelle Genois ◽  
Qi Liu ◽  
Shan Lu ◽  
...  
Keyword(s):  
Dna Replication ◽  
Single Molecule ◽  
Replication Stress ◽  
Proton Radiation ◽  
Wild Type ◽  
Cellular Effects ◽  
Proton Treatment ◽  
Dna Replication Stress ◽  
Fork Stalling ◽  
Mutant Cells

AbstractMutant KRAS is a common tumor driver and frequently confers resistance to anti-cancer treatments such as radiation. DNA replication stress in these tumors may constitute a therapeutic liability but is poorly understood. Here, using single-molecule DNA fiber analysis, we first characterized baseline replication stress in a panel of unperturbed isogenic and non-isogenic cancer cell lines. Correlating with the observed enhanced replication stress we found increased levels of cytosolic double-stranded DNA in KRAS mutant compared to wild-type cells. Yet, despite this phenotype replication stress-inducing agents failed to selectively impact KRAS mutant cells, which were protected by CHK1. Similarly, most exogenous stressors studied did not differentially augment cytosolic DNA accumulation in KRAS mutant compared to wild-type cells. However, we found that proton radiation was able to slow fork progression and preferentially induce fork stalling in KRAS mutant cells. Proton treatment also partly reversed the radioresistance associated with mutant KRAS. The cellular effects of protons in the presence of KRAS mutation clearly contrasted that of other drugs affecting replication, highlighting the unique nature of the underlying DNA damage caused by protons. Taken together, our findings provide insight into the replication stress response associated with mutated KRAS, which may ultimately yield novel therapeutic opportunities.

Yeast dom34 Mutants Are Defective in Multiple Developmental Pathways and Exhibit Decreased Levels of Polyribosomes

Genetics ◽  
1998 ◽  
Vol 149 (1) ◽  
pp. 45-56
Author(s):  
Luther Davis ◽  
JoAnne Engebrecht
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Heterologous Expression ◽  
Protein Translation ◽  
Developmental Pathways ◽  
G1 Phase ◽  
Growth Defect ◽  
Wild Type ◽  
Drosophila Homolog ◽  
Mutant Cells

Abstract The DOM34 gene of Saccharomyces cerevisiae is similar togenes found in diverse eukaryotes and archaebacteria. Analysis of dom34 strains shows that progression through the G1 phase of the cell cycle is delayed, mutant cells enter meiosis aberrantly, and their ability to form pseudohyphae is significantly diminished. RPS30A, which encodes ribosomal protein S30, was identified in a screen for high-copy suppressors of the dom34Δ growth defect. dom34Δ mutants display an altered polyribosome profile that is rescued by expression of RPS30A. Taken together, these data indicate that Dom34p functions in protein translation to promote G1 progression and differentiation. A Drosophila homolog of Dom34p, pelota, is required for the proper coordination of meiosis and spermatogenesis. Heterologous expression of pelota in dom34Δ mutants restores wild-type growth and differentiation, suggesting conservation of function between the eukaryotic members of the gene family.

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