Spongiform Neurodegeneration-associated E3 Ligase Mahogunin Ubiquitylates TSG101 and Regulates Endosomal Trafficking

A null mutation in the gene encoding the putative E3 ubiquitin–protein ligase Mahogunin causes spongiform neurodegeneration, a recessively transmitted prion-like disease in mice. However, no substrates of Mahogunin have been identified, and the cellular role of Mahogunin is unknown. Here, we report the identification of TSG101, a key component of the endosomal sorting complex required for transport (ESCRT)-I, as a specific Mahogunin substrate. We find that Mahogunin interacts with the ubiquitin E2 variant (UEV) domain of TSG101 via its PSAP motif and that it catalyzes monoubiquitylation of TSG101 both in vivo and in vitro. Depletion of Mahogunin by small interfering RNAs in mammalian cells disrupts endosome-to-lysosome trafficking of epidermal growth factor receptor, resulting in prolonged activation of a downstream signaling cascade. Our findings support a role for Mahogunin in a proteasome-independent ubiquitylation pathway and suggest a link between dysregulation of endosomal trafficking and spongiform neurodegeneration.

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The secreted Salmonella dublin phosphoinositide phosphatase, SopB, localizes to PtdIns(3)P-containing endosomes and perturbs normal endosome to lysosome trafficking

Biochemical Journal ◽

10.1042/bj20051451 ◽

2006 ◽

Vol 395 (2) ◽

pp. 239-247 ◽

Cited By ~ 38

Author(s):

Joseph D. Dukes ◽

Huailo Lee ◽

Rachel Hagen ◽

Barbara J. Reaves ◽

Abigail N. Layton ◽

...

Keyword(s):

Mammalian Cells ◽

Growth Factor Receptor ◽

Secretion Systems ◽

Endosomal Sorting ◽

Salmonella Dublin ◽

Phosphoinositide Phosphatase ◽

Type Iii Secretion Systems ◽

Epidermal Growth

Invasion and survival in mammalian cells by Salmonella enterica is mediated by bacterial proteins that are delivered to the host cell cytoplasm by type III secretion systems. One of these proteins, SopB/SigD, is a phosphoinositide phosphatase that can hydrolyse a number of substrates in vitro including PtdIns(3,5)P2. These substrates are, however, likely to be restricted in vivo by the localization of SopB, as different phosphoinositides have distinct spatial distributions in mammalian cells. In the present study, we show that heterologously expressed SopB localizes almost exclusively to endosomes containing the lipid PtdIns(3)P, and on which ESCRT (endosomal sorting complexes required for transport) proteins assemble. Furthermore, we present evidence that SopB can inhibit trafficking of activated epidermal growth factor receptor to the lysosome. These results provide further evidence that PtdIns(3,5)P2, a lipid involved in endosomal maturation, may be a relevant in vivo substrate of SopB. We hypothesize that reduction of PtdIns(3,5)P2 levels in cells by the action of SopB may perturb the function of a subset of ESCRT proteins that have previously been shown to bind to this lipid.

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Enhanced expression of EGF receptor in a model of salt-sensitive hypertension

AJP Renal Physiology ◽

10.1152/ajprenal.00003.2005 ◽

2005 ◽

Vol 289 (2) ◽

pp. F314-F321 ◽

Cited By ~ 19

Author(s):

Wei-Zhong Ying ◽

Paul W. Sanders

Keyword(s):

Egf Receptor ◽

Primary Cultures ◽

Growth Factor Receptor ◽

Sprague Dawley ◽

Renal Vasculature ◽

Downstream Signaling ◽

Egfr Expression ◽

Enhanced Expression

Chronic kidney disease in the Dahl/Rapp salt-sensitive (S) rat is related to an arteriolopathic process that occurs following the onset of hypertension and involves vascular smooth muscle cell (VSMC) hyperplasia and luminal constriction. Because previous studies have shown that activation of the epidermal growth factor receptor (EGFR) produces a mitogenic stimulus in VSMC and the EGFR participates integrally in the vasoconstrictor responses of renal arterioles, the present study analyzed the expression of EGFR in these animals. Compared with Sprague-Dawley (SD) rats, renal cortical expression of EGFR was increased in both prehypertensive and hypertensive S rats. Immunohistochemistry using a polyclonal antibody to EGFR demonstrated that EGFR expression was prominent in the renal vasculature, particularly in the media of afferent and efferent arterioles and the aorta of S rats. When examined, primary cultures of VSMC from S rats showed increased expression of EGFR, compared with VSMC from SD and Dahl/Rapp salt-resistant rats. Following addition of EGF, autophosphorylation of the EGFR was enhanced in cells from S rats, as was the downstream signaling events that included activation of p42/44 MAPK and Akt pathways. Thus in vivo and in vitro studies demonstrated augmented expression and functional activity of the EGFR in S rats.

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Src Inhibitors Pyrazolo[3,4-d]pyrimidines, Si306 and Pro-Si306, Inhibit Focal Adhesion Kinase and Suppress Human Glioblastoma Invasion In Vitro and In Vivo

Cancers ◽

10.3390/cancers12061570 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1570 ◽

Cited By ~ 1

Author(s):

Marija Nešović ◽

Aleksandra Divac Rankov ◽

Ana Podolski-Renić ◽

Igor Nikolić ◽

Goran Tasić ◽

...

Keyword(s):

Focal Adhesion Kinase ◽

Focal Adhesion ◽

Growth Factor Receptor ◽

Similar Efficacy ◽

Src Tyrosine Kinase ◽

Downstream Signaling ◽

Egfr Expression ◽

Human Gbm

Glioblastoma (GBM), as the most aggressive brain tumor, displays a high expression of Src tyrosine kinase, which is involved in the survival, migration, and invasiveness of tumor cells. Thus, Src emerged as a potential target for GBM therapy. The effects of Src inhibitors pyrazolo[3,4-d]pyrimidines, Si306 and its prodrug pro-Si306 were investigated in human GBM cell lines (U87 and U87-TxR) and three primary GBM cell cultures. Primary GBM cells were more resistant to Si306 and pro-Si306 according to the 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. However, the ability of all GBM cells to degrade the extracellular matrix was considerably compromised after Si306 and pro-Si306 applications. Besides reducing the phosphorylation of Src and its downstream signaling pathway components, both compounds decreased the phosphorylated form of focal adhesion kinase (FAK) and epidermal growth factor receptor (EGFR) expression, showing the potential to suppress the aggressiveness of GBM. In vivo, Si306 and pro-Si306 displayed an anti-invasive effect against U87 xenografts in the zebrafish embryo model. Considering that Si306 and pro-Si306 are able to cross the blood–brain barrier and suppress the spread of GBM cells, we anticipate their clinical testing in the near future. Moreover, the prodrug showed similar efficacy to the drug, implying the rationality of its use in clinical settings.

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AMPylation matches BiP activity to client protein load in the endoplasmic reticulum

eLife ◽

10.7554/elife.12621 ◽

2015 ◽

Vol 4 ◽

Cited By ~ 64

Author(s):

Steffen Preissler ◽

Cláudia Rato ◽

Ruming Chen ◽

Robin Antrobus ◽

Shujing Ding ◽

...

Keyword(s):

Endoplasmic Reticulum ◽

Mammalian Cells ◽

Atp Hydrolysis ◽

Covalent Modification ◽

Dependent Manner ◽

Gene Encoding ◽

Unfolded Protein ◽

Peptide Dissociation

The endoplasmic reticulum (ER)-localized Hsp70 chaperone BiP affects protein folding homeostasis and the response to ER stress. Reversible inactivating covalent modification of BiP is believed to contribute to the balance between chaperones and unfolded ER proteins, but the nature of this modification has so far been hinted at indirectly. We report that deletion of FICD, a gene encoding an ER-localized AMPylating enzyme, abolished detectable modification of endogenous BiP enhancing ER buffering of unfolded protein stress in mammalian cells, whilst deregulated FICD activity had the opposite effect. In vitro, FICD AMPylated BiP to completion on a single residue, Thr518. AMPylation increased, in a strictly FICD-dependent manner, as the flux of proteins entering the ER was attenuated in vivo. In vitro, Thr518 AMPylation enhanced peptide dissociation from BiP 6-fold and abolished stimulation of ATP hydrolysis by J-domain cofactor. These findings expose the molecular basis for covalent inactivation of BiP.

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SH3KBP1 Promotes Glioblastoma Tumorigenesis by Activating EGFR Signaling

Frontiers in Oncology ◽

10.3389/fonc.2020.583984 ◽

2021 ◽

Vol 10 ◽

Author(s):

Hai Song ◽

Yanpei Wang ◽

Chaojia Shi ◽

Jianxiang Lu ◽

Tian Yuan ◽

...

Keyword(s):

Growth Factor Receptor ◽

Adaptor Protein ◽

Egfr Signaling ◽

Potential Therapeutic Target ◽

Downstream Signaling ◽

Protein Levels ◽

Egfr Activation ◽

Epidermal Growth

Glioblastoma (GBM) is the most common and aggressive brain tumor in adults. Overexpression or activation of epidermal growth factor receptor (EGFR) occurs commonly in multiple human cancers and promotes tumorigenesis. However, the underlying molecular mechanism of EGFR aberrant activation and the downstream signaling pathways remains largely unknown. In this study, we report that both SH3-domain kinase binding protein 1 (SH3KBP1) mRNA and protein levels are highly expressed in GBM and its high expression is associated with worse survival of glioma patients. In addition, we provide evidence that SH3KBP1 is prominently expressed in GBM stem cells (GSCs) and have potential to serve as a novel GSCs marker. Moreover, silencing SH3KBP1 dramatically impairs GBM cell proliferation, migration and GSCs self-renewal ability in vitro and xenograft tumors growth in vivo. Most importantly, we found that SH3KBP1 directly interacts with EGFR and may act as an adaptor protein to transduce EGFR signaling. Together, our work uncovers SH3KBP1 as a novel regulator of oncogenic EGFR signaling and also as a potential therapeutic target for GBM patients with EGFR activation.

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Primaquine Inhibits the Endosomal Trafficking and Nuclear Localization of EGFR and Induces the Apoptosis of Breast Cancer Cells by Nuclear EGFR/Stat3-Mediated c-Myc Downregulation

International Journal of Molecular Sciences ◽

10.3390/ijms222312961 ◽

2021 ◽

Vol 22 (23) ◽

pp. 12961

Author(s):

Ji-Hyang Kim ◽

Hack-Sun Choi ◽

Dong-Sun Lee

Keyword(s):

Breast Cancer ◽

Cancer Cells ◽

Breast Cancer Cells ◽

Nuclear Translocation ◽

Growth Factor Receptor ◽

Endosomal Trafficking ◽

Protein Levels ◽

Early Endosomes

Triple-negative breast cancer (TNBC) cells overexpress the epidermal growth factor receptor (EGFR). Nuclear EGFR (nEGFR) drives resistance to anti-EGFR therapy and is correlated with poor survival in breast cancer. Inhibition of EGFR nuclear translocation may be a reasonable approach for the treatment of TNBC. The anti-malarial drugs chloroquine and primaquine have been shown to promote an anticancer effect. The aim of the present study was to investigate the effect and mechanism of chloroquine- and primaquine-induced apoptosis of breast cancer cells. We showed that primaquine, a malaria drug, inhibits the growth, migration, and colony formation of breast cancer cells in vitro, and inhibits tumor growth in vivo. Primaquine induces damage to early endosomes and inhibits the nuclear translocation of EGFR. Primaquine inhibits the interaction of Stat3 and nEGFR and reduces the transcript and protein levels of c-Myc. Moreover, primaquine and chloroquine induce the apoptosis of breast cancer cells through c-Myc/Bcl-2 downregulation, induce early endosome damage and reduce nEGFR levels, and induce apoptosis in breast cancer through nEGFR/Stat3-dependent c-Myc downregulation. Our study of primaquine and chloroquine provides a rationale for targeting EGFR signaling components in the treatment of breast cancer.

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Lenvatinib suppresses cancer stem-like cells in HCC by inhibiting FGFR1–3 signaling, but not FGFR4 signaling

Carcinogenesis ◽

10.1093/carcin/bgaa049 ◽

2020 ◽

Cited By ~ 1

Author(s):

Taku Shigesawa ◽

Osamu Maehara ◽

Goki Suda ◽

Mitsuteru Natsuizaka ◽

Megumi Kimura ◽

...

Keyword(s):

Fibroblast Growth Factor Receptor ◽

Growth Factor Receptor ◽

Polymerase Chain Reaction Analysis ◽

Small Interfering Rnas ◽

First Line ◽

Multikinase Inhibitor ◽

Polymerase Chain ◽

And Control

Abstract In hepatocellular carcinoma (HCC), a subset of cells defined by high CD44 and CD133 expression has been reported to possess cancer stem-like cell (CSC) characteristics and to be associated with a poor prognosis. Since the approval of the multikinase inhibitor, lenvatinib, for patients with unresectable HCC, two such inhibitors (sorafenib and lenvatinib) have been employed as first-line systemic chemotherapeutics for these patients. Based on differences in the kinase-affinity profiles between these two drugs, evidence has suggested that both exert different effects on HCC, although these differences are not fully characterized. In this study, using in vitro and a preclinical in vivo xenograft mouse model, we showed that lenvatinib alone (not sorafenib or the cytotoxic agent, 5-fluorouracil) diminished CD44High/CD133High CSCs in HCC. Furthermore, western blotting and reverse transcriptase-polymerase chain reaction analysis revealed that the expression of fibroblast growth factor receptor (FGFR)-1–4 differed between CD44High/CD133High CSCs and control cells. Analysis of the effects of selective FGFR inhibitors and FGFR small interfering RNAs on CSCs in HCC revealed that lenvatinib diminished CSCs in HCC by inhibiting FGFR1–3 signaling, however, FGFR4 signaling was not impacted. Finally, we showed that FGF2 and FGF19 were involved in maintaining CD44High/CD133High CSCs in HCC, potentially, via FGFR1–3. The findings provide novel mechanistic insights into the effects of lenvatinib on CSCs in HCC and provide clues for developing effective targeted therapies against CSCs in HCC.

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Vacuoles Induced in Mammalian Cells by Helicobacter Cytotoxin are Acidic Organelles

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100158388 ◽

1990 ◽

Vol 48 (3) ◽

pp. 168-169

Author(s):

M. H. Chestnut ◽

C. E. Catrenich

Keyword(s):

Acridine Orange ◽

Mammalian Cells ◽

Laser Scanning ◽

Laser Scanning Microscopy ◽

Confocal Laser ◽

Ulcer Disease ◽

Gastroduodenal Disease ◽

H Pylori

Helicobacter pylori is a non-invasive, Gram-negative spiral bacterium first identified in 1983, and subsequently implicated in the pathogenesis of gastroduodenal disease including gastritis and peptic ulcer disease. Cytotoxic activity, manifested by intracytoplasmic vacuolation of mammalian cells in vitro, was identified in 55% of H. pylori strains examined. The vacuoles increase in number and size during extended incubation, resulting in vacuolar and cellular degeneration after 24 h to 48 h. Vacuolation of gastric epithelial cells is also observed in vivo during infection by H. pylori. A high molecular weight, heat labile protein is believed to be responsible for vacuolation and to significantly contribute to the development of gastroduodenal disease in humans. The mechanism by which the cytotoxin exerts its effect is unknown, as is the intracellular origin of the vacuolar membrane and contents. Acridine orange is a membrane-permeant weak base that initially accumulates in low-pH compartments. We have used acridine orange accumulation in conjunction with confocal laser scanning microscopy of toxin-treated cells to begin probing the nature and origin of these vacuoles.

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Cytological changes induced by platinum-thymine in sarcoma-180 cells: Electron microscopy study

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010015900x ◽

1990 ◽

Vol 48 (3) ◽

pp. 290-291

Author(s):

Gustav Ofosu

Keyword(s):

Mammalian Cells ◽

Antitumor Agent ◽

Microscopy Study ◽

Electron Microscopy Study ◽

Limiting Factor ◽

Sarcoma 180 ◽

Electron Microscopic ◽

Cytological Changes

Platinum-thymine has been found to be a potent antitumor agent, which is quite soluble in water, and lack nephrotoxicity as the dose-limiting factor. The drug has been shown to interact with DNA and inhibits DNA, RNA and protein synthesis in mammalian cells in vitro. This investigation was undertaken to elucidate the cytotoxic effects of piatinum-thymine on sarcoma-180 cells in vitro ultrastructurally, Sarcoma-180 tumor bearing mice were treated with intraperitoneal injection of platinum-thymine 40mg/kg. A concentration of 60μg/ml dose of platinum-thymine was used in in vitro experiments. Treatments were at varying time intervals of 3, 7 and 21 days for in vivo experiments, and 30, 60 and 120 min., 6, 12, and 24th in vitro. Controls were not treated with platinum-thymine.Electron microscopic analyses of the treated cells in vivo and in vitro showed drastic cytotoxic effect.

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Programmable in vitro Co-Encapsidation of Guest Proteins Inside Protein Nanocages

10.26434/chemrxiv.5844393 ◽

2018 ◽

Author(s):

Noor H. Dashti ◽

Rufika S. Abidin ◽

Frank Sainsbury

Keyword(s):

Self Assembly ◽

Mammalian Cells ◽

Resonance Energy Transfer ◽

Resonance Energy ◽

Super Resolution ◽

Cell Engineering ◽

Particle Analysis ◽

Protein Cages

Bioinspired self-sorting and self-assembling systems using engineered versions of natural protein cages have been developed for biocatalysis and therapeutic delivery. The packaging and intracellular delivery of guest proteins is of particular interest for both in vitro and in vivo cell engineering. However, there is a lack of platforms in bionanotechnology that combine programmable guest protein encapsidation with efficient intracellular uptake. We report a minimal peptide anchor for in vivo self-sorting of cargo-linked capsomeres of the Murine polyomavirus (MPyV) major coat protein that enables controlled encapsidation of guest proteins by in vitro self-assembly. Using Förster resonance energy transfer (FRET) we demonstrate the flexibility in this system to support co-encapsidation of multiple proteins. Complementing these ensemble measurements with single particle analysis by super-resolution microscopy shows that the stochastic nature of co-encapsidation is an overriding principle. This has implications for the design and deployment of both native and engineered self-sorting encapsulation systems and for the assembly of infectious virions. Taking advantage of the encoded affinity for sialic acids ubiquitously displayed on the surface of mammalian cells, we demonstrate the ability of self-assembled MPyV virus-like particles to mediate efficient delivery of guest proteins to the cytosol of primary human cells. This platform for programmable co-encapsidation and efficient cytosolic delivery of complementary biomolecules therefore has enormous potential in cell engineering.

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