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

2006 ◽  
Vol 395 (2) ◽  
pp. 239-247 ◽  
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.

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

2007 ◽  
Vol 18 (4) ◽  
pp. 1129-1142 ◽  
Author(s):  
Bong Yoon Kim ◽  
James A. Olzmann ◽  
Gregory S. Barsh ◽  
Lih-Shen Chin ◽  
Lian Li
Keyword(s):  
Mammalian Cells ◽  
Growth Factor Receptor ◽  
Endosomal Trafficking ◽  
Small Interfering Rnas ◽  
Gene Encoding ◽  
Endosomal Sorting ◽  
Ubiquitin Protein Ligase ◽  
Downstream Signaling

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.

Toxicity and efficacy evaluation of multiple targeted polymalic acid conjugates for triple-negative breast cancer treatment

2020 ◽  
Author(s):  
Lungwani Muungo
Keyword(s):  
Triple Negative ◽  
Growth Factor Receptor ◽  
Engineered Nanoparticles ◽  
Efficacy Evaluation ◽  
Dual Action ◽  
Epidermal Growth ◽  
Laminin 411 ◽  
Immunologic Analysis

Engineered nanoparticles are widely used for delivery of drugs but frequently lack proof of safetyfor cancer patient's treatment. All-in-one covalent nanodrugs of the third generation have beensynthesized based on a poly(β-L-malic acid) (PMLA) platform, targeting human triple-negativebreast cancer (TNBC). They significantly inhibited tumor growth in nude mice by blockingsynthesis of epidermal growth factor receptor, and α4 and β1 chains of laminin-411, the tumorvascular wall protein and angiogenesis marker. PMLA and nanodrug biocompatibility and toxicityat low and high dosages were evaluated in vitro and in vivo. The dual-action nanodrug and singleactionprecursor nanoconjugates were assessed under in vitro conditions and in vivo with multipletreatment regimens (6 and 12 treatments). The monitoring of TNBC treatment in vivo withdifferent drugs included blood hematologic and immunologic analysis after multiple intravenousadministrations. The present study demonstrates that the dual-action nanoconju-gate is highlyeffective in preclinical TNBC treatment without side effects, supported by hematologic andimmunologic assays data. PMLA-based nanodrugs of the Polycefin™ family passed multipletoxicity and efficacy tests in vitro and in vivo on preclinical level and may prove to be optimizedand efficacious for the treatment of cancer patients in the future.

scholarly journals Imaging-Guided Therapy Simultaneously Targeting HER2 and EpCAM with Trastuzumab and EpCAM-Directed Toxin Provides Additive Effect in Ovarian Cancer Model

Cancers ◽  
2021 ◽  
Vol 13 (16) ◽  
pp. 3939
Author(s):  
Tianqi Xu ◽  
Anzhelika Vorobyeva ◽  
Alexey Schulga ◽  
Elena Konovalova ◽  
Olga Vorontsova ◽  
...  
Keyword(s):  
Ovarian Cancer ◽  
Growth Factor Receptor ◽  
Repeated Administration ◽  
Ovarian Cancer Cells ◽  
Her2 Positive ◽  
Efficient Treatment ◽  
Pseudomonas Exotoxin A ◽  
Epidermal Growth

Efficient treatment of disseminated ovarian cancer (OC) is challenging due to its heterogeneity and chemoresistance. Overexpression of human epidermal growth factor receptor 2 (HER2) and epithelial cell adhesion molecule (EpCAM) in approx. 30% and 70% of ovarian cancers, respectively, allows for co-targeted treatment. The clinical efficacy of the monoclonal antibody trastuzumab in patients with HER2-positive breast, gastric and gastroesophageal cancers makes it readily available as the HER2-targeting component. As the EpCAM-targeting component, we investigated the designed ankyrin repeat protein (DARPin) Ec1 fused to a truncated variant of Pseudomonas exotoxin A with reduced immunogenicity and low general toxicity (LoPE). Ec1-LoPE was radiolabeled, evaluated in ovarian cancer cells in vitro and its biodistribution and tumor-targeting properties were studied in vivo. The therapeutic efficacy of Ec1-LoPE alone and in combination with trastuzumab was studied in mice bearing EpCAM- and HER2-expressing SKOV3 xenografts. SPECT/CT imaging enabled visualization of EpCAM and HER2 expression in the tumors. Co-treatment using Ec1-LoPE and trastuzumab was more effective at reducing tumor growth and prolonged the median survival of mice compared with mice in the control and monotherapy groups. Repeated administration of Ec1-LoPE was well tolerated without signs of hepatic or kidney toxicity. Co-treatment with trastuzumab and Ec1-LoPE might be a potential therapeutic strategy for HER2- and EpCAM-positive OC.

scholarly journals Disruption of TP63-miR-27a* Feedback Loop by Mutant TP53 in Head and Neck Cancer

2019 ◽  
Vol 112 (3) ◽  
pp. 266-277 ◽  
Author(s):  
Nikhil S Chari ◽  
Cristina Ivan ◽  
Xiandong Le ◽  
Jinzhong Li ◽  
Ainiwaer Mijiti ◽  
...  
Keyword(s):  
Epidermal Growth Factor Receptor ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Oral Cavity ◽  
Head And Neck ◽  
Feedback Loop ◽  
Growth Factor Receptor ◽  
Epidermal Growth

Abstract Background Alterations in the epidermal growth factor receptor and PI3K pathways in head and neck squamous cell carcinomas (HNSCCs) are frequent events that promote tumor progression. Ectopic expression of the epidermal growth factor receptor–targeting microRNA (miR), miR-27a* (miR-27a-5p), inhibits tumor growth. We sought to identify mechanisms mediating repression of miR-27a* in HNSCC, which have not been previously identified. Methods We quantified miR-27a* in 47 oral cavity squamous cell carcinoma patient samples along with analysis of miR-27a* in 73 oropharyngeal and 66 human papillomavirus–positive (HPV+) samples from The Cancer Genome Atlas. In vivo and in vitro TP53 models engineered to express mutant TP53, along with promoter analysis using chromatin immunoprecipitation and luciferase assays, were used to identify the role of TP53 and TP63 in miR-27a* transcription. An HNSCC cell line engineered to conditionally express miR-27a* was used in vitro to determine effects of miR-27a* on target genes and tumor cells. Results miR-27a* expression was repressed in 47 oral cavity tumor samples vs matched normal tissue (mean log2 difference = −0.023, 95% confidence interval = −0.044 to −0.002; two-sided paired t test, P = .03), and low miR-27a* levels were associated with poor survival in HPV+ and oropharyngeal HNSCC samples. Binding of ΔNp63α to the promoter led to an upregulation of miR-27a*. In vitro and in vivo findings showed that mutant TP53 represses the miR-27a* promoter, downregulating miR-27a* levels. ΔNp63α and nucleoporin 62, a protein involved in ΔNP63α transport, were validated as novel targets of miR-27a*. Conclusion Our results characterize a negative feedback loop between TP63 and miR-27a*. Genetic alterations in TP53, a frequent event in HNSCC, disrupt this regulatory loop by repressing miR-27a* expression, promoting tumor survival.

scholarly journals VPS37A directs ESCRT recruitment for phagophore closure

2019 ◽  
Vol 218 (10) ◽  
pp. 3336-3354 ◽  
Author(s):  
Yoshinori Takahashi ◽  
Xinwen Liang ◽  
Tatsuya Hattori ◽  
Zhenyuan Tang ◽  
Haiyan He ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Growth Factor Receptor ◽  
Multivesicular Body ◽  
Regulatory Mechanisms ◽  
Endosomal Sorting ◽  
Aaa Atpase ◽  
Escrt Machinery ◽  
Genome Wide ◽  
A Genome ◽  
Epidermal Growth

The process of phagophore closure requires the endosomal sorting complex required for transport III (ESCRT-III) subunit CHMP2A and the AAA ATPase VPS4, but their regulatory mechanisms remain unknown. Here, we establish a FACS-based HaloTag-LC3 autophagosome completion assay to screen a genome-wide CRISPR library and identify the ESCRT-I subunit VPS37A as a critical component for phagophore closure. VPS37A localizes on the phagophore through the N-terminal putative ubiquitin E2 variant domain, which is found to be required for autophagosome completion but dispensable for ESCRT-I complex formation and the degradation of epidermal growth factor receptor in the multivesicular body pathway. Notably, loss of VPS37A abrogates the phagophore recruitment of the ESCRT-I subunit VPS28 and CHMP2A, whereas inhibition of membrane closure by CHMP2A depletion or VPS4 inhibition accumulates VPS37A on the phagophore. These observations suggest that VPS37A coordinates the recruitment of a unique set of ESCRT machinery components for phagophore closure in mammalian cells.

scholarly journals An endosomally localized isoform of Eps15 interacts with Hrs to mediate degradation of epidermal growth factor receptor

2008 ◽  
Vol 180 (6) ◽  
pp. 1205-1218 ◽  
Author(s):  
Ingrid Roxrud ◽  
Camilla Raiborg ◽  
Nina Marie Pedersen ◽  
Espen Stang ◽  
Harald Stenmark
Keyword(s):  
Epidermal Growth Factor Receptor ◽  
Growth Factor ◽  
Epidermal Growth Factor ◽  
Growth Factor Receptor ◽  
Adaptor Protein ◽  
Coated Pits ◽  
Kinase Substrate ◽  
Epidermal Growth

Down-regulation of activated and ubiquitinated growth factor (GF) receptors by endocytosis and subsequent lysosomal degradation ensures attenuation of GF signaling. The ubiquitin-binding adaptor protein Eps15 (epidermal growth factor receptor [EGFR] pathway substrate 15) functions in endocytosis of such receptors. Here, we identify an Eps15 isoform, Eps15b, and demonstrate its expression in human cells and conservation across vertebrate species. Although both Eps15 and Eps15b interact with the endosomal sorting protein Hrs (hepatocyte growth factor–regulated tyrosine kinase substrate) in vitro, we find that Hrs specifically binds Eps15b in vivo (whereas adaptor protein 2 preferentially interacts with Eps15). Although Eps15 mainly localizes to clathrin-coated pits at the plasma membrane, Eps15b localizes to Hrs-positive microdomains on endosomes. Eps15b overexpression, similarly to Hrs overexpression, inhibits ligand-mediated degradation of EGFR, whereas Eps15 is without effect. Similarly, depletion of Eps15b but not Eps15 delays degradation and promotes recycling of EGFR. These results indicate that Eps15b is an endosomally localized isoform of Eps15 that is present in the Hrs complex via direct Hrs interaction and important for the sorting function of this complex.

scholarly journals Role of PARP1-mediated autophagy in EGFR-TKI resistance in non-small cell lung cancer

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Zhimin Zhang ◽  
Xiaojuan Lian ◽  
Wei Xie ◽  
Jin Quan ◽  
Maojun Liao ◽  
...  
Keyword(s):  
Lung Cancer ◽  
Kinase Inhibitors ◽  
Growth Factor Receptor ◽  
Advanced Lung Cancer ◽  
Tki Resistance ◽  
Geo Dataset ◽  
Epidermal Growth

AbstractResistance to epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) has become the main clinical challenge of advanced lung cancer. This research aimed to explore the role of PARP1-mediated autophagy in the progression of TKI therapy. PARP1-mediated autophagy was evaluated in vitro by CCK-8 assay, clonogenic assay, immunofluorescence, and western blot in the HCC-827, H1975, and H1299 cells treated with icotinib (Ico), rapamycin, and AZD2281 (olaparib) alone or in combination. Our results and GEO dataset analysis confirmed that PARP1 is expressed at lower levels in TKI-sensitive cells than in TKI-resistant cells. Low PARP1 expression and high p62 expression were associated with good outcomes among patients with NSCLC after TKI therapy. AZD2281 and a lysosomal inhibitor reversed resistance to Ico by decreasing PARP1 and LC3 in cells, but an mTOR inhibitor did not decrease Ico resistance. The combination of AZD2281 and Ico exerted a markedly enhanced antitumor effect by reducing PARP1 expression and autophagy in vivo. Knockdown of PARP1 expression reversed the resistance to TKI by the mTOR/Akt/autophagy pathway in HCC-827IR, H1975, and H1299 cells. PARP1-mediated autophagy is a key pathway for TKI resistance in NSCLC cells that participates in the resistance to TKIs. Olaparib may serve as a novel method to overcome the resistance to TKIs.

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