scholarly journals Impact on Autophagy and Ultraviolet B Induced Responses of Treatment with the MTOR Inhibitors Rapamycin, Everolimus, Torin 1, and pp242 in Human Keratinocytes

2017 ◽  
Vol 2017 ◽  
pp. 1-21 ◽  
Author(s):  
Song Xu ◽  
Li Li ◽  
Min Li ◽  
Mengli Zhang ◽  
Mei Ju ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Cellular Response ◽  
Mtor Inhibitors ◽  
Mtor Signaling ◽  
Ultraviolet B ◽  
Epidermal Keratinocytes ◽  
Human Epidermal Keratinocytes ◽  
Mtor Inhibition ◽  
The Impact ◽  
Uva Radiation

The mechanistic target of Rapamycin (MTOR) protein is a crucial signaling regulator in mammalian cells that is extensively involved in cellular biology. The function of MTOR signaling in keratinocytes remains unclear. In this study, we detected the MTOR signaling and autophagy response in the human keratinocyte cell line HaCaT and human epidermal keratinocytes treated with MTOR inhibitors. Moreover, we detected the impact of MTOR inhibitors on keratinocytes exposed to the common carcinogenic stressors ultraviolet B (UVB) and UVA radiation. As a result, keratinocytes were sensitive to the MTOR inhibitors Rapamycin, everolimus, Torin 1, and pp242, but the regulation of MTOR downstream signaling was distinct. Next, autophagy induction only was observed in HaCaT cells treated with Rapamycin. Furthermore, we found that MTOR signaling was insensitive to UVB but sensitive to UVA radiation. UVB treatment also had no impact on the inhibition of MTOR signaling by MTOR inhibitors. Finally, MTOR inhibition by Rapamycin, everolimus, or pp242 did not affect the series of biological events in keratinocytes exposed to UVB, including the downregulation of BiP and PERK, activation of Histone H2A and JNK, and cleavage of caspase-3 and PARP. Our study demonstrated that MTOR inhibition in keratinocytes cannot always induce autophagy, and the MTOR pathway does not play a central role in the UVB triggered cellular response.

scholarly journals Functional Impacts of the BRCA1-mTORC2 Interaction in Breast Cancer

2019 ◽  
Vol 20 (23) ◽  
pp. 5876 ◽  
Author(s):  
Kimiko L. Krieger ◽  
Wen-Feng Hu ◽  
Tyler Ripperger ◽  
Nicholas T. Woods
Keyword(s):  
Breast Cancer ◽  
Dna Damage ◽  
Cancer Cells ◽  
Breast Cancer Cells ◽  
Mtor Inhibitors ◽  
Mtor Signaling ◽  
Protein Domain ◽  
Mtor Inhibition ◽  
Increased Risk ◽  
The Impact

Deleterious mutations in Breast Cancer 1 (BRCA1) are associated with an increased risk of breast and ovarian cancer. Mutations in the tandem BRCA1 C-terminal (tBRCT) protein domain disrupt critical protein interactions required for the faithful repair of DNA through homologous recombination, which contributes to oncogenesis. Our studies have identified RICTOR, PRR5, and SIN1 subunits of the mammalian target of rapamycin complex 2 (mTORC2) as interacting partners with the tBRCT domain of BRCA1 leading to the disruption of the mTORC2 complex. However, the interplay between mTORC2 signaling and BRCA1 function in the DNA damage response (DDR) remains to be determined. In this study, we used protein interaction assays to determine the binary interactions between the tBRCT domain and mTORC2 subunits, evaluated the impact of mTOR inhibition on the transcriptional function of the tBRCT, evaluated the impact of mTOR signaling on BRCA1 recruitment to DNA damage-induced foci and determined the breast cancer cell line response to mTOR inhibition dependent upon BRCA1 expression and mutation. This study determined that PRR5, RICTOR, and SIN1 could each independently interact with the BRCA1 tBRCT. Inhibition of mTORC1, but not mTORC1/2, increases BRCA1 transcriptional activation activity. Treatment with pan-mTOR inhibitor PP242 diminishes DNA damage-induced γH2AX and BRCA1 foci formation. Breast cancer cells lacking expression of functional BRCA1 are more sensitive to mTOR inhibitors. These data suggest that mTOR signaling is required for BRCA1 response to DNA damage and breast cancer cells lacking BRCA1 are more sensitive to pan-mTOR inhibition. This work suggests chemotherapeutic strategies using mTOR inhibitors could be tailored for patients that lack functional BRCA1.

1439PRAS40 attenuates mTOR-dependent endothelial inflammation and atherosclerosis

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
K Zhang ◽  
J Schecker ◽  
K Woeltje ◽  
A Krull ◽  
V Stangl ◽  
...  
Keyword(s):  
Endothelial Cells ◽  
Mtor Inhibitors ◽  
Negative Regulation ◽  
Mtor Signaling ◽  
Adhesion Assay ◽  
Inflammatory Signaling ◽  
Endothelial Inflammation ◽  
Carotid Ligation ◽  
Mtorc1 Signaling ◽  
The Impact

Abstract Introduction Endothelial inflammation plays a pivotal role in atherosclerosis. Many inflammatory and metabolic signals converge upon mechanistic target of rapamycin (mTOR), and inhibition of mTOR has been shown to reduce atherosclerosis. However, clinical use of mTOR-inhibitors is limited by serious adverse effects, of which insulin resistance and dyslipidemia are particularly troubling in the context of atherosclerosis. In that respect, targeting PRAS40, an endogenous modulator of mTOR complex 1 (mTORC1) with highly cell type-specific effects on mTOR signaling, may be a more promising approach. In fact, we have previously demonstrated that, in contrast to conventional mTOR inhibitors, PRAS40 gene therapy substantially improves metabolic profile in obese mice. However, the function of PRAS40 in endothelial cells and its role in atherosclerosis have never been investigated. Methods and results To define the impact of PRAS40 on endothelial mTORC1-signaling in this context, cultured human umbilical vein endothelial cells (HUVECs) were exposed to the atherogenic cytokine TNFα. TNFα induced mTOR signaling as evidenced by increased phosphorylation of S6 kinase and ribosomal S6 protein. Interestingly, this effect was strongly augmented upon siRNA-mediated knock-down of PRAS40, indicating a negative regulation of mTORC1 by PRAS40 in endothelial cells. Moreover, PRAS40-knockdown promoted TNFα-induced inflammatory signaling as reflected by increased proliferative activity, upregulation of atherogenic markers like CCL2 and VCAM-1, as well as enhanced monocyte recruitment in the THP-1 adhesion assay. In contrast, PRAS40-overexpression blocked TNFα-induced activation of mTORC1 and consistently suppressed all of these measures of inflammatory activation. All effects of PRAS40-overexpression could be reproduced by the mTORC1 inhibitors rapamycin and torin1. Thus, our in vitro studies suggest that in endothelial cells PRAS40 exerts anti-atherogenic effects by negative regulation of mTORC1. To validate these findings in vivo in the context of atherosclerosis we created transgenic mice with tamoxifen-inducible endothelium-specific PRAS40-deficiency (EC-PRAS40-KO). These mice were exposed to a model of accelerated atherosclerosis based on western diet and partial carotid ligation: Four weeks after partial carotid ligation, neointimal and atherosclerotic lesion formation was strongly enhanced in EC-PRAS40-KO mice. Moreover, mTORC1 activity as well as CCL2 and VCAM-1 expression were markedly increased compared to control mice. Conclusion Our data indicate that PRAS40 suppresses atherosclerosis via inhibition of mTORC1-mediated inflammatory signaling in endothelial cells. In conjunction with its favourable effects on metabolic homeostasis, the overall therapeutic profile of PRAS40-treatment appears to be beneficial compared to conventional mTOR-inhibitors. Taken together PRAS40 may qualify as a promising therapeutic target for the treatment of atherosclerosis. Acknowledgement/Funding German Federal Ministry of Education and Research, DZHK (German Centre for Cardiovascular Research)

scholarly journals Differential Effects of Endoplasmic Reticulum Stress-induced Autophagy on Cell Survival

2006 ◽  
Vol 282 (7) ◽  
pp. 4702-4710 ◽  
Author(s):  
Wen-Xing Ding ◽  
Hong-Min Ni ◽  
Wentao Gao ◽  
Yi-Feng Hou ◽  
Melissa A. Melan ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Death ◽  
Endoplasmic Reticulum Stress ◽  
Cell Survival ◽  
Cancer Cells ◽  
Mammalian Cells ◽  
Cellular Response ◽  
Brefeldin A ◽  
Human Colon ◽  
The Impact

Autophagy is a cellular response to adverse environment and stress, but its significance in cell survival is not always clear. Here we show that autophagy could be induced in the mammalian cells by chemicals, such as A23187, tunicamycin, thapsigargin, and brefeldin A, that cause endoplasmic reticulum stress. Endoplasmic reticulum stress-induced autophagy is important for clearing polyubiquitinated protein aggregates and for reducing cellular vacuolization in HCT116 colon cancer cells and DU145 prostate cancer cells, thus mitigating endoplasmic reticulum stress and protecting against cell death. In contrast, autophagy induced by the same chemicals does not confer protection in a normal human colon cell line and in the non-transformed murine embryonic fibroblasts but rather contributes to cell death. Thus the impact of autophagy on cell survival during endoplasmic reticulum stress is likely contingent on the status of cells, which could be explored for tumor-specific therapy.

scholarly journals Ultraviolet B, melanin and mitochondrial DNA: Photo-damage in human epidermal keratinocytes and melanocytes modulated by alpha-melanocyte-stimulating hormone

F1000Research ◽  
2016 ◽  
Vol 5 ◽  
pp. 881 ◽  
Author(s):  
Markus Böhm ◽  
Helene Z. Hill
Keyword(s):  
Mitochondrial Dna ◽  
Copy Number ◽  
Cell Types ◽  
Ultraviolet B ◽  
Epidermal Keratinocytes ◽  
Human Epidermal Keratinocytes ◽  
Mtdna Damage ◽  
Melanocyte Stimulating Hormone ◽  
Copy Numbers ◽  
Stimulating Hormone

Alpha-melanocyte-stimulating hormone (alpha-MSH) increases melanogenesis and protects from UV-induced DNA damage. However, its effect on mitochondrial DNA (mtDNA) damage is unknown. We have addressed this issue in a pilot study using human epidermal keratinocytes and melanocytes incubated with alpha-MSH and irradiated with UVB. Real-time touchdown PCR was used to quantify total and deleted mtDNA. The deletion detected encompassed the common deletion but was more sensitive to detection. There were 4.4 times more mtDNA copies in keratinocytes than in melanocytes. Irradiation alone did not affect copy numbers. Alpha-MSH slightly increased copy numbers in both cell types in the absence of UVB and caused a similar small decrease in copy number with dose in both cell types. Deleted copies were nearly twice as frequent in keratinocytes as in melanocytes. Alpha-MSH reduced the frequency of deleted copies by half in keratinocytes but not in melanocytes. UVB dose dependently led to an increase in the deleted copy number in alpha-MSH-treated melanocytes. UVB irradiation had little effect on deleted copy number in alpha-MSH-treated keratinocytes. In summary, alpha-MSH enhances mtDNA damage in melanocytes presumably by increased melanogenesis, while α-MSH is protective in keratinocytes, the more so in the absence of irradiation.

mTOR Signaling Is Required for the Survival and Proliferation of Hematopoietic Stem/Progenitor Cells

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 4787-4787
Author(s):  
Xia Xiao ◽  
Hongmei Luo ◽  
Amanda C. LaRue ◽  
Bradley A. Schulte ◽  
Yong Wang
Keyword(s):  
Progenitor Cells ◽  
Cell Transformation ◽  
Conflicts Of Interest ◽  
Mtor Inhibitors ◽  
Mtor Signaling ◽  
Immunofluorescent Staining ◽  
Mouse Bone Marrow ◽  
Mtor Inhibition ◽  
Hematopoietic Stem

Abstract Abstract 4787 The mammalian target of rapamycin (mTOR) is a serine/threonine kinase that regulates protein synthesis, gene transcription, cell growth and cell proliferation. Previous studies have demonstrated that abnormalities in the Pten-mTOR pathway may contribute to the development of leukemia and lead to premature exhaustion of hematopoietic stem cells (HSCs). These findings suggest a role for mTOR in the regulation of HSC self-renewal and cell transformation. The aim of this study was to investigate the involvement of mTOR signaling in the survival and proliferation of HSCs and hematopoietic progenitor cells (HPCs). Immunofluorescent staining with antibodies against phosphorylated mTOR and S6 kinase revealed that Thrombopoietin (Tpo) activates mTOR in cultured mouse bone marrow (BM) lineage negative cells, suggesting that Tpo may promote the survival and proliferation of HSCs/HPCs via activation of the mTOR signaling pathway. Further studies revealed that treatment with an mTOR specific small molecule inhibitor (Ku-69734) significantly suppressed the colony-forming ability of HPCs as evidenced by a dose-dependent decrease in the production of CFU-GM, BFU-E and CFU-GEMM. We also examined the clonogenic function of HSCs using cobblestone-area forming cell (CAFC) assays and found that Ku-69734 treatment markedly reduced the number of CAFCs in long-term BM culture. Moreover, immunophenotyping and flow cytometric analyses showed that inhibition of mTOR induced apoptosis primarily in HSCs and to a lesser degree in HPCs, indicating that mTOR inhibition may suppress the clonogenic function of HSCs and HPCs via the induction of apoptosis. Together, these data demonstrate that mTOR signaling is required for the survival and proliferation of HSCs and HPCs. Given that many mTOR inhibitors are currently in clinical trials for the treatment of cancers, our findings provide the rationale to further evaluate the potential toxicity of mTOR inhibitors in HSCs/HPCs in vivo. Disclosures: No relevant conflicts of interest to declare.

Dichotomous effect of ultraviolet B on the expression of corneodesmosomal enzymes in human epidermal keratinocytes

2009 ◽  
Vol 54 (1) ◽  
pp. 17-24 ◽  
Author(s):  
Megumi Nin ◽  
Norito Katoh ◽  
Satoshi Kokura ◽  
Osamu Handa ◽  
Toshikazu Yoshikawa ◽  
...  
Keyword(s):  
Ultraviolet B ◽  
Epidermal Keratinocytes ◽  
Human Epidermal Keratinocytes
Sign in / Sign up

Export Citation Format

Share Document