874 research outputs found
Bahumukhī mana, bahurupī prema
No full textThe document contains a novel written by the Bengali author Nirpendra Kumar Basu (1898-1979). The monograph is from the private collection of Sharmadip Basu
Regulation of protein kinase C-η in breast cancer cells
No full textProtein kinase C-η (PKCη) is involved in cell proliferation, differentiation and plays an anti-apoptotic role in various cancer models. The purpose of this dissertation is to understand the regulation of PKCη in cell death signaling in breast cancer cells.
Tumor promoting phorbol esters are potent activators of PKC and prolonged treatment with these activators leads to downregulation and desensitization of PKC signaling. PKCη resists phorbol ester-induced downregulation and upregulated in response to prolonged treatment. We have found that phosphorylation of PKCη at conserved serine/threonine sites is increased by phorbol ester treatment. Single mutations that prevent phosphorylation at these conserved sites resulted in downregulation of PKCη. These results suggest that phosphorylation of PKCη at conserved sites prevents its downregulation.
We have found that PKCη can be significantly downregulated by inhibition of two pathways: PKC and phosphoinositide 3-kinase (PI3K) using pharmacological inhibitors. Inhibitors of PKC and PI3K induce dephosphorylation of PKCη by a calyculin A-specific phosphatase. These inhibitors differ in their ability to degrade PKCη via the proteasome-mediated pathway. Downregulation of PKCη by PKC inhibitor is not mediated by the proteasome degradation pathway, whereas downregulation by PI3K inhibitor is dependent on the proteasome. These results demonstrate that dephosphorylation is important for PKCη downregulation and this occurs through two distinct mechanisms.
A comparison of PKC protein levels in a series of isogenic cell lines representing a breast cancer progression model revealed that PKCη protein levels increased from the normal, benign stage to the pre-malignant and metastatic stages. These results indicate that PKCη plays a potential role in breast cancer progression. Further analysis indicated that overexpression of PKCη in the MCF-7 breast adenocarcinoma cell line conferred resistance to tumor necrosis factor-alpha-related apoptosis-inducing ligand (TRAIL)-induced cell death. Therefore, PKCη protects breast cancer cells from TRAIL-induced apoptosis. Depletion of PKCη by small interfering RNA (siRNA) resulted in increased dimerization of pro-apoptotic Bax and decreased induction of anti-apoptotic Mcl-1 by TRAIL. These results indicate that PKCη may exert its anti-apoptotic effect by targeting Bcl-2 proteins, Bax and Mcl-1
Transcriptional regulation of the human RLIP76 gene
No full textA 76-kDa Ral-interacting protein (RLIP76) has been implicated in the pathogenesis of cancer and diabetes. It is often overexpressed in human malignant cell lines and human tumor samples and has been associated with metastasis and chemoresistance. RLIP76 homozygous knockout mice exhibit increased insulin sensitivity, hypoglycemia, and hypolipidemia, and resist cancer development. Little is known about the mechanism by which the expression of RLIP76 is regulated. In the present study, we functionally characterized the RLIP76 promoter using deletion mapping and mutational analysis to investigate the regulation of RLIP76 transcription. We have identified the promoter regions important for RLIP76 transcription, including a strong positive cis-acting element (-167 to -152) in the proximal promoter containing overlapping consensus cMYB and cETS binding sites. Transcription factor cMYB and the coactivator p300 associate with the RLIP76 gene promoter as shown by CHIP assay. Knockdown of p300 in cells reduces the activity of the promoter fragment containing wild type cMYB/cETS binding site in comparison to that with deleted or mutated cMYB/cETS binding site. Knockdown of p300 also decreases the RLIP76 expression as indicated by immunoblotting, immunocytochemistry and flow cytometry analysis. Thus, we report for the first time that p300 associates with the RLIP76 promoter via overlapping cMYB and cETS binding sites and regulates RLIP76 promoter activity and expression in HEK293 and MCF7 cells
Protein Kinase C-eta Signalling in Breast Cancer
No full textPal, Deepanwita, Protein kinase C-eta signaling in breast cancer. Doctor of Philosophy (Biochemistry and Molecular Biology), November, 2013, 117 pp, 14 illustrations, 260 References Protein kinase C-eta (PKCη) is a novel member of the PKC family that is important for several cellular processes. PKCη is overexpressed in breast cancer and has been associated with chemotherapeutic resistance. PKCη is the only phorbol ester-sensitive PKC isozyme that resists downregulation upon prolonged treatment with tumorpromoting phorbol esters suggesting its unique regulation. The purpose of this dissertation is to elucidate the mechanism of PKCη regulation and its functional relevance in breast cancer. We have shown that PKCη is upregulated by several structurally and functionally distinct PKC activators in contrast to other PKC isozymes. Activator-induced upregulation of PKCη was associated with its phosphorylation. Our results indicate that novel PKCs are involved in the upregulation of PKCη by PKC activators. We also made a novel observation that PKCη is downregulated via two distinct mechanisms. While inhibition of PKC caused the downregulation of PKCη via proteasome-independent pathway, inhibition of PDK1 led to PKCη downregulation via proteasome-dependent pathway. We further demonstrated that PKCη is important for the growth and survival of breast cancer cells. The unique regulation of PKCη and its implications on breast cancer growth and survival suggests that this pathway could be selectively exploited for targeted therapies for breast cancer
Dissecting the Role of Protein Kinase C-Epsilon in Breast Cancer
No full textProtein kinase C-epsilon (PKCε) has pro-tumor functions in many cancers including breast cancer. The purpose of this dissertation is to understand the role of PKCε in fundamental processes that are associated with breast cancer development and progression.
PKCε is known to promote the survival of breast cancer cells. Autophagy is a process of cellular self-digestion that can mediate cell survival during stress. We have found that PKCε overexpression increases the basal autophagy in breast cancer cells while its depletion reduces it. Moreover, the effect of PKCε on autophagy is isozyme specific. Regulation by PKCε is not limited to basal autophagy as it also mediated starvation-induced autophagy. Looking for the possible mechanisms, we found that PKCε negatively regulates mammalian target of rapamycin (mTOR), which is the master regulator of autophagy. These results show that PKCε positively regulates autophagy, likely, via inhibition of mTOR.
PKCε overexpression in mammary epithelial cells led to morphological changes indicating its role in regulation of cell plasticity. Further analysis revealed that PKCε promotes epithelial to mesenchymal transition (EMT), which is an early step in cancer metastasis. In addition, PKCε mediated transforming growth factor-beta (TGFβ)-induced EMT partially via Snail, which is a crucial EMT effector. Moreover, PKCε promoted cell migration and anoikis Ii resistance which are hallmarks of EMT. To examine the phenotypic effect of PKCε manipulation in a physiologically relevant context, we employed three dimensional (3D) cell culture model. We found that PKCε overexpression led to disruption of acinar morphogenesis in 3D culture. These results indicate a causal role for PKCε in breast tumor development and progressio
Outer Length Scales in Nocturnal Stable Boundary Layers
No full textRecently, Basu and Holstlag (2021) proposed a unified framework for describing outer length scales (OLS). By utilizing this framework, we document various characteristics of OLS in nocturnal boundary layers over the US Great Plains.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Atmospheric Remote Sensin
Involvement of S6 Kinase in Breast Cancer
No full textSridharan, S., Involvement of S6 Kinase in Breast Cancer. Doctor of Philosophy (Cancer Biology), November 2013, 129pp, 19 illustrations, 215 references. The 40S ribosomal protein S6 Kinase (S6K) is activated downstream of the mammalian target of rapamycin (mTOR)and is believed to play and important role in protein translation. In mammalian cells S6K is represented by two highly homologous proteins, S6K1 and S6K2. Both homologs have been shown to be amplicfied and over expressed in breast cancer cells and tissues. While the regulation and functions of S6K1 have been addressed, little is known about those of S6K2 . Hence we sought to examine the causes and consequences of elevated S6K2 levels in breast cancer cells. While the depletion of S6K1 decreased breast cancer cell death, silencing of S6K2 substantially increased it in response to apoptotic and chemotherapeutic agents. We then explored the mechanism by which S6K2 mediates survival and observed that in contrast to S6K1, S6K2 depletion decreased the activation of the prosurvival protein Akt and increased the level of proapoptotic proteins p53 and bid. Following this observation, we sought to determine the pathways(s) contributing to the overexpression of S6K2 in breast cancer cells. Due to its role as a prognostic indicator in estrogen receptor (ER) – positive tumors, we studied the role of the estrogen signaling pathways in regulating S6K2 levels. Estradiol and estrogen receptor alpha (ERα) positively regulated S6K2 protein but did not affect its mRNA levels, suggesting post-transcriptional regulation. We further observed that S6K2 regulated cell survival downstream of estrogen in ER-positive breast cancer cells. These findings strongly suggest that S6K2 is critical for the survival of breast cancer cells and that targeting S6K2 in combination with chemotherapeutic agents is a novel strategy to promote breast cancer cell death
Regulation of Autophagy by Protein Kinase C-ε in Breast Cancer Cells
No full textProtein kinase C-ε (PKCε), an anti-apoptotic protein, plays critical roles in breast cancer development and progression. Although autophagy is an important survival mechanism, it is not known if PKCε regulates autophagy in breast cancer cells. We have shown that silencing of PKCε by siRNA inhibited basal and starvation-induced autophagy in T47D breast cancer cells as determined by the decrease in LC3-II, increase in p62, and decrease in autophagy puncta both in the presence and absence of bafilomycin A1. The mechanistic target of rapamycin (mTOR) associates with Raptor or Rictor to form complex-1 (mTORC1) or complex-2 (mTORC2), respectively. Knockdown of PKCε attenuated an increase in autophagy caused by the depletion of Raptor and Rictor. Overexpression of PKCε in MCF-7 cells caused activation of mTORC1 and an increase in LC3-I, LC3-II, and p62. The mTORC1 inhibitor rapamycin abolished the increase in LC3-I and p62. Knockdown of mTOR and Rictor or starvation enhanced autophagy in PKCε overexpressing cells. While overexpression of PKCε in MCF-7 cells inhibited apoptosis, it induced autophagy in response to tumor necrosis factor-α. However, inhibition of autophagy by Atg5 knockdown restored apoptosis in PKCε-overexpressing cells. Thus, PKCε promotes breast cancer cell survival not only by inhibiting apoptosis but also by inducing autophagy
The Enigmatic Protein Kinase C-eta
No full textThe purpose of this review article is to discuss how PKCη regulates various cellular processes that may contribute to its contrasting roles in cancer. Protein kinase C-eta (PKCη) is a unique member of the PKC family since its regulation is distinct from other PKC isozymes. PKCη was shown to regulate cell proliferation, differentiation and cell death
Cupid Joins the War
No full textThe author explores the history of love and sex in war though the ages. This monograph is from the private collection of Sharmadip Basu, Kolkata, W.B., India
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