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References | 17 Available | See All References
|Reference overview||Species||Pub Med ID|
|Wnt proteins regulate acetylcholine receptor clustering in muscle cells. |
Bin Zhang,Chuan Liang,Ryan Bates,Yiming Yin,Wen-Cheng Xiong,Lin Mei
Molecular brain 5 2012
The neuromuscular junction (NMJ) is a cholinergic synapse that rapidly conveys signals from motoneurons to muscle cells and exhibits a high degree of subcellular specialization characteristic of chemical synapses. NMJ formation requires agrin and its coreceptors LRP4 and MuSK. Increasing evidence indicates that Wnt signaling regulates NMJ formation in Drosophila, C. elegans and zebrafish.
|The metastasis gene NEDD9 product acts through integrin β3 and Src to promote mesenchymal motility and inhibit amoeboid motility. |
Jessica Ahn,Victoria Sanz-Moreno,Christopher J Marshall
Journal of cell science 125 2012
Neural precursor expressed, developmentally down-regulated 9 (NEDD9), a member of the Cas family of signal transduction molecules, is amplified at the genetic level in melanoma, and elevated expression levels have been shown to correlate with melanoma progression and metastasis. NEDD9 interacts with the guanine nucleotide exchange factor DOCK3 to promote Rac activation and the elongated, mesenchymal-type of tumour cell invasion, but the molecular mechanisms through which NEDD9 promotes melanoma metastasis are not fully understood. We show that signalling through increased NEDD9 levels requires integrin β3 signalling, which leads to elevated phosphorylation of integrin β3. This results in increased Src and FAK but decreased ROCK signalling to drive elongated, mesenchymal-type invasion in environments that contain vitronectin. NEDD9 overexpression does not affect ROCK signalling through activation of RhoA but decreases ROCKII signalling through Src-dependent phosphorylation of a negative regulatory site Tyr722. In NEDD9-overexpressing melanoma cells, inhibition of Src with dasatinib results in a switch from Rac-driven elongated, mesenchymal-type invasion to ROCK-dependent rounded, amoeboid invasion. These findings brings into question whether dasatinib would work as a therapeutic agent to block melanoma invasion and metastasis. On the basis of the in vitro data presented here, a combination treatment of dasatinib and a ROCK inhibitor might be a better alternative in order to inhibit both elongated, mesenchymal-type and rounded, amoeboid motility.
|Pro-neural miR-128 is a glioma tumor suppressor that targets mitogenic kinases. |
T Papagiannakopoulos,D Friedmann-Morvinski,P Neveu,J C Dugas,R M Gill,E Huillard,C Liu,H Zong,D H Rowitch,B A Barres,I M Verma,K S Kosik
Oncogene 31 2012
MicroRNAs (miRNAs) carry out post-transcriptional control of a multitude of cellular processes. Aberrant expression of miRNA can lead to diseases, including cancer. Gliomas are aggressive brain tumors that are thought to arise from transformed glioma-initiating neural stem cells (giNSCs). With the use of giNSCs and human glioblastoma cells, we investigated the function of miRNAs in gliomas. We identified pro-neuronal miR-128 as a candidate glioma tumor suppressor miRNA. Decreased expression of miR-128 correlates with aggressive human glioma subtypes. With a combination of molecular, cellular and in vivo approaches, we characterize miR-128's tumor suppressive role. miR-128 represses giNSC growth by enhancing neuronal differentiation. miR-128 represses growth and mediates differentiation by targeting oncogenic receptor tyrosine kinases (RTKs) epithelial growth factor receptor and platelet-derived growth factor receptor-Î±. Using an autochthonous glioma mouse model, we demonstrated that miR-128 repressed gliomagenesis. We identified miR-128 as a glioma tumor suppressor that targets RTK signaling to repress giNSC self-renewal and enhance differentiation.
|Prolactin-induced activation of phagocyte NADPH oxidase in the teleost fish gilthead seabream involves the phosphorylation of p47phox by protein kinase C. |
Víctor H Olavarría,Jaime E Figueroa,Victoriano Mulero
Developmental and comparative immunology 36 2012
The pituitary hormone prolactin (PRL) is a multifunctional polypeptide which act as a key component of the neuroendocrine-immune loop and as a local regulator of the macrophage response. The involvement of PRL in regulating monocyte/macrophage functions is suggested by the presence of PRL receptors in these cells. Recently, we reported that physiological concentrations of native PRL were able to induce the expression of the pro-inflammatory cytokines IL-1? and TNF?, and the production of reactive oxygen species (ROS) in head kidney leukocytes and macrophages from the teleost fish gilthead seabream (Sparus aurata L.). In this study, we show that the NADPH oxidase subunit p47phox becomes phosphorylated in leukocytes stimulated with PRL, an effect that is blocked when neutralizing polyclonal antibodies to PRL are added. Additionally, the pharmacological inhibition of either protein kinase C (PKC) with calphostin C or the Jak/Stat signaling pathway with AG490 impaired PKC activation, p47phox phosphorylation and ROS production in seabream leukocytes activated with PRL. Taken together, our results demonstrate for the first time the need for PKC in regulating the PRL-mediated phosphorylation of p47phox, the activation of NADPH oxidase and the production of ROS by macrophages in vertebrates.
|Identification of a Src tyrosine kinase/SIAH2 E3 ubiquitin ligase pathway that regulates C/EBP? expression and contributes to transformation of breast tumor cells. |
Tapasree Roysarkar,Shikha Sharan,Jun Wang,Snehalata A Pawar,Carrie A Cantwell,Peter F Johnson,Deborah K Morrison,Ju-Ming Wang,Esta Sterneck,Tapasree Roy Sarkar,Tapasree Roy Sarkar
Molecular and cellular biology 32 2012
The transcription factor CCAAT/enhancer-binding protein delta (C/EBP?, CEBPD) is a tumor suppressor that is downregulated during breast cancer progression but may also promote metastasis. Here, we have investigated the mechanism(s) regulating C/EBP? expression and its role in human breast cancer cells. We describe a novel pathway by which the tyrosine kinase Src downregulates C/EBP? through the SIAH2 E3 ubiquitin ligase. Src phosphorylates SIAH2 in vitro and leads to tyrosine phosphorylation and activation of SIAH2 in breast tumor cell lines. SIAH2 interacts with C/EBP?, but not C/EBP?, and promotes its polyubiquitination and proteasomal degradation. Src/SIAH2-mediated inhibition of C/EBP? expression supports elevated cyclin D1 levels, phosphorylation of retinoblastoma protein (Rb), motility, invasive properties, and survival of transformed cells. Pharmacological inhibition of Src family kinases by SKI-606 (bosutinib) induces C/EBP? expression in an SIAH2-dependent manner, which is necessary for therapeutic responses to SKI-606 in vitro. Ectopic expression of degradation-resistant mutants of C/EBP?, which do not interact with SIAH2 and/or cannot be polyubiquitinated, prevents full transformation of MCF-10A cells by activated Src (Src truncated at amino acid 531 [Src-531]) in vitro. These data reveal that C/EBP? expression can be regulated at the protein level by oncogenic Src kinase signals through SIAH2, thus contributing to breast epithelial cell transformation.
|Omega-3 fatty acids modulate collagen signaling in human platelets. |
Larson, M K, et al.
Prostaglandins Leukot. Essent. Fatty Acids, 84: 93-8 2011
Dietary intake of the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) results in cardioprotective benefits. However, the cellular and physiological bases for these benefits remain unclear. We hypothesized that EPA and DHA treatments would interfere with collagen-mediated platelet signaling. Thirty healthy volunteers received 28 days of 3.4g/d EPA+DHA with and without a single dose of aspirin. Clinical hematologic parameters were then measured along with assays of collagen-stimulated platelet activation and protein phosphorylation. Omega-3 therapy led to a small but significant reduction in platelets (6.3%) and red blood cells (1.7%), but did not impair clinical time-to-closure assays. However, collagen-mediated platelet signaling events of integrin activation, α-granule secretion, and phosphatidylserine exposure were all reduced by roughly 50% after omega-3 incorporation, and collagen-induced tyrosine phosphorylation was significantly impaired. The diminished platelet response to collagen may account for some of the cardioprotective benefits provided by DHA and EPA.
|Beta-catenin inhibits T cell activation by selective interference with linker for activation of T cells-phospholipase C-γ1 phosphorylation. |
Driessens G, Zheng Y, Locke F, Cannon JL, Gounari F, Gajewski TF
J Immunol 186 784-90. Epub 2010 Dec 13. 2011
Despite the defined function of the β-catenin pathway in thymocytes, its functional role in peripheral T cells is poorly understood. We report that in a mouse model, β-catenin protein is constitutively degraded in peripheral T cells. Introduction of stabilized β-catenin into primary T cells inhibited proliferation and cytokine secretion after TCR stimulation and blunted effector cell differentiation. Functional and biochemical studies revealed that β-catenin selectively inhibited linker for activation of T cells phosphorylation on tyrosine 136, which was associated with defective phospholipase C-γ1 phosphorylation and calcium signaling but normal ERK activation. Our findings indicate that β-catenin negatively regulates T cell activation by a previously undescribed mechanism and suggest that conditions under which β-catenin might be inducibly stabilized in vivo would be inhibitory for T cell-based immunity.
|A PATHOBIOLOGICAL ROLE OF THE INSULIN RECEPTOR IN CHRONIC LYMPHOCYTIC LEUKEMIA. |
Saiya-Cork K, Collins R, Parkin B, Ouillette P, Kuizon E, Kujawski L, Erba H, Campagnaro E, Shedden K, Kaminski M, Malek SN
Clin Cancer Res 2011
PURPOSE: The chromosomal deletion 11q affects biology and clinical outcome in CLL but del11q-deregulated genes remain incompletely characterized.EXPERIMENTAL DESIGN: We have employed integrated genomic profiling approaches upon CLL cases with and without del11q to identify 11q-relevant genes.RESULTS: We have identified differential expression of the insulin receptor (INSR) in CLL, including high-level INSR expression in the majority of CLL with del11q. High INSR mRNA expression in 11q CLL (~10-fold higher mean levels than other genomic categories) was confirmed by Q-PCR in 247 CLL cases. INSR protein measurements in 257 CLL cases through FACS, compared with measurements in normal CD19+ B-cells and monocytes, confirmed that a subset of CLL aberrantly expresses high INSR levels. INSR stimulation by insulin in CLL cells ex vivo resulted in the activation of canonical INSR signaling pathways, including the AKT-mTOR and Ras/Raf/Erk pathways, and INSR activation partially abrogated spontaneous CLL cell apoptosis ex vivo. Higher INSR levels correlated with shorter time to first therapy (TTFT) and shorter overall survival (OS). In bivariate analysis, INSR expression predicted for rapid initial disease progression and shorter OS in ZAP-70 low/negative CLL. Finally, in multivariate analysis (ZAP-70 status, IgVH status and INSR expression), we detected elevated hazard ratios and trends for short OS for CLL cases with high INSR expression (analyzed inclusive or exclusive of cases with del11q).CONCLUSIONS: Our aggregate biochemical and clinical outcome data suggest biologically meaningful elevated INSR expression in a substantial subset of all CLL cases, including many cases with del11q.
|Participation of the cell polarity protein PALS1 to T-cell receptor-mediated NF-κB activation. |
Carvalho, Gabrielle, et al.
PLoS ONE, 6: e18159 (2011) 2011
Beside their established function in shaping cell architecture, some cell polarity proteins were proposed to participate to lymphocyte migration, homing, scanning, as well as activation following antigen receptor stimulation. Although PALS1 is a central component of the cell polarity network, its expression and function in lymphocytes remains unknown. Here we investigated whether PALS1 is present in T cells and whether it contributes to T Cell-Receptor (TCR)-mediated activation.
|Osmotic stress stimulates phosphorylation and cellular expression of heat shock proteins in rhesus macaque sperm. |
Cole JA, Meyers SA
Journal of andrology 32 402-10. Epub 2010 Nov 18. 2011
The cryosurvival of sperm requires cell signaling mechanisms to adapt to anisotonic conditions during the freezing and thawing process. Chaperone proteins heat shock protein 70 (HSP 70) and heat shock protein 90 (HSP 90; recently renamed HSPA and HSPC, respectively) facilitate some of these cell signaling events in somatic cells. Sperm were evaluated for their cellular expression and levels of phosphorylation of both HSP 70 and HSP 90 under anisotonic conditions as a potential model for cell signaling during the cryopreservation of macaque spermatozoa. In order to monitor the level of stress, the motility and viability parameters were evaluated at various time points. Cells were then either prepared for phosphoprotein enrichment or indirect immunocytochemistry. As controls, the phosphoserine, phosphothreonine, and phosphotyrosine levels were measured under capacitation and cryopreservation conditions and were compared with the phosphoprotein levels expressed under osmotic conditions. As expected, there was an increase in the level of tyrosine phosphorylation under capacitation and cryopreservation conditions. There was also a significant increase in the level of all phosphoproteins under hyperosmotic conditions. There was no change in the level of expression of HSP 70 or 90 under osmotic stress conditions as measured by Western blot. The enrichment of phosphoproteins followed by Western immunoblotting revealed an increase in the phosphorylation of HSP 70 but not HSP 90 under osmotic stress conditions. Indirect immunofluorescence localized HSP 70 to the postacrosomal region of sperm, and the level of membrane expression of HSP 70 was significantly affected by anisotonic conditions, as measured by flow cytometry. Taken together, these results suggest a differential role for HSP 70 and HSP 90 during osmotic stress conditions in rhesus macaque sperm.
|GILZ inhibits the mTORC2/AKT pathway in BCR-ABL(+) cells. |
Joha, S, et al.
Oncogene, (2011) 2011
The malignant phenotype of chronic myeloid leukemia (CML) is due to the abnormal tyrosine kinase activity of the BCR-ABL oncoprotein, which signals several downstream cell survival pathways, including phosphoinositide 3-kinase/AKT, signal transducer and activator of transcription 5 and extracellular signal-regulated kinase 1/2. In patients with CML, tyrosine kinase inhibitors (TKIs) are used to suppress the BCR-ABL tyrosine kinase, resulting in impressive response rates. However, resistance can occur, especially in acute-phase CML, through various mechanisms. Here, we show that the glucocorticoid-induced leucine zipper protein (GILZ) modulates imatinib and dasatinib resistance and suppresses tumor growth by inactivating the mammalian target of rapamycin complex-2 (mTORC2)/AKT signaling pathway. In mouse and human models, GILZ binds to mTORC2, but not to mTORC1, inhibiting phosphorylation of AKT (at Ser473) and activating FoxO3a-mediated transcription of the pro-apoptotic protein Bim; these results demonstrate that GILZ is a key inhibitor of the mTORC2 pathway. Furthermore, CD34(+) stem cells isolated from relapsing CML patients underwent apoptosis and showed inhibition of mTORC2 after incubation with glucocorticoids and imatinib. Our findings provide new mechanistic insights into the role of mTORC2 in BCR-ABL(+) cells and indicate that regulation by GILZ may influence TKI sensitivity.Oncogene advance online publication, 1 August 2011;doi:10.1038/onc.2011.328.
|Cytoskeletal polarity mediates localized induction of the heart progenitor lineage. |
James Cooley,Stacia Whitaker,Sarah Sweeney,Scott Fraser,Brad Davidson
Nature cell biology 13 2011
Cells must make appropriate fate decisions within a complex and dynamic environment. In vitro studies indicate that the cytoskeleton acts as an integrative platform for this environmental input. External signals regulate cytoskeletal dynamics and the cytoskeleton reciprocally modulates signal transduction. However, in vivo studies linking cytoskeleton/signalling interactions to embryonic cell fate specification remain limited. Here we show that the cytoskeleton modulates heart progenitor cell fate. Our studies focus on differential induction of heart fate in the basal chordate Ciona intestinalis. We have found that differential induction does not simply reflect differential exposure to the inductive signal. Instead, pre-cardiac cells employ polarized, invasive protrusions to localize their response to an ungraded signal. Through targeted manipulation of the cytoskeletal regulator CDC42, we are able to depolarize protrusive activity and generate uniform heart progenitor fate specification. Furthermore, we are able to restore differential induction by repolarizing protrusive activity. These findings illustrate how bi-directional interactions between intercellular signalling and the cytoskeleton can influence embryonic development. In particular, these studies highlight the potential for dynamic cytoskeletal changes to refine cell fate specification in response to crude signal gradients.
|Prolactin-induced Jak2 phosphorylation of RUSH: a key element in Jak/RUSH signaling. |
Rebecca A Helmer,Marlyn Panchoo,Janet S Dertien,Suhani M Bhakta,Aveline Hewetson,Beverly S Chilton
Molecular and cellular endocrinology 325 2010
Jak2/Stat-mediated prolactin signaling culminates in Stat5a-DNA-binding. However, not all Jak2-dependent genes have Stat5 sites. Western analysis with inhibitors showed Jak2 is a proximal intermediate in prolactin-induced RUSH phosphorylation. Transfection assays with HRE-H9 cells showed the RUSH-binding site mediated the ability of prolactin to augment progesterone-dependent transcription of the RUSH gene. Jak2 inhibitors or targeted RUSH-site mutation blocked the prolactin effect. RUSH co-immunoprecipitated with phospho-Jak2 from nuclear extracts. Jak2 inhibitors abolished the nuclear pool of phospho-RUSH not the nuclear content of RUSH in HRE-H9 cells. Nucleolar-affiliated partners, e.g. nucleolin, were identified by microLC/MS/MS analysis of nuclear proteins that co-immunoprecipitated with RUSH/GST-RING. RUSH did not exclusively co-localize with fibrillarin to the nucleolus. MG-132 (proteasomal inhibitor) failed to block Tyrene CR4-mediated decrease in phospho-RUSH, and did not promote RUSH accumulation in the nucleolus. These studies authenticate prolactin-dependent Jak2 phosphorylation of RUSH, and provide functional implications on the RUSH network of nuclear interactions.Full Text Article
|Autophagy-mediated insulin receptor down-regulation contributes to endoplasmic reticulum stress-induced insulin resistance. |
Zhou L, Zhang J, Fang Q, Liu M, Liu X, Jia W, Dong LQ, Liu F
Molecular pharmacology 76 596-603 Epub 2009 Jun 18 2009
Endoplasmic reticulum (ER) stress is associated with obesity-induced insulin resistance, yet the underlying mechanisms remain to be fully elucidated. Here we show that ER stress-induced insulin receptor (IR) down-regulation may play a critical role in obesity-induced insulin resistance. The expression levels of IR are negatively associated with the ER stress marker C/EBP homologous protein (CHOP) in insulin target tissues of db/db mice and mice fed a high-fat diet. Significant IR down-regulation was also observed in fat tissue of obese human subjects and in 3T3-L1 adipocytes treated with ER stress inducers. ER stress had little effect on IR tyrosine phosphorylation per se but greatly reduced IR downstream signaling. The ER stress-induced reduction in IR cellular levels was greatly alleviated by the autophagy inhibitor 3-methyladenine but not by the proteasome inhibitor N-benzoyloxycarbonyl (Z)-Leu-Leu-leucinal (MG132). Inhibition of autophagy prevented IR degradation but did not rescue IR downstream signaling, consistent with an adaptive role of autophagy in response to ER stress-induced insulin resistance. Finally, chemical chaperone treatment protects cells from ER stress-induced IR degradation in vitro and obesity-induced down-regulation of IR and insulin action in vivo. Our results uncover a new mechanism underlying obesity-induced insulin resistance and shed light on potential targets for the prevention and treatment of obesity-induced insulin resistance and type 2 diabetes.Full Text Article
|An adaptor role for cytoplasmic Sam68 in modulating Src activity during cell polarization. |
Marc-Etienne Huot,Claire M Brown,Nathalie Lamarche-Vane,Stéphane Richard
Molecular and cellular biology 29 2009
The Src-associated substrate during mitosis with a molecular mass of 68 kDa (Sam68) is predominantly nuclear and is known to associate with proteins containing the Src homology 3 (SH3) and SH2 domains. Although Sam68 is a Src substrate, little is known about the signaling pathway that link them. Src is known to be activated transiently after cell spreading, where it modulates the activity of small Rho GTPases. Herein we report that Sam68-deficient cells exhibit loss of cell polarity and cell migration. Interestingly, Sam68-deficient cells exhibited sustained Src activity after cell attachment, resulting in the constitutive tyrosine phosphorylation and activation of p190RhoGAP and its association with p120rasGAP. Consistently, we observed that Sam68-deficient cells exhibited deregulated RhoA and Rac1 activity. By using total internal reflection fluorescence microscopy, we observed Sam68 near the plasma membrane after cell attachment coinciding with phosphorylation of its C-terminal tyrosines and association with Csk. These findings show that Sam68 localizes near the plasma membrane during cell attachment and serves as an adaptor protein to modulate Src activity for proper signaling to small Rho GTPases.Full Text Article
|The role of HSP70 on ENPP1 expression and insulin-receptor activation. |
Marucci, Antonella, et al.
J. Mol. Med., 87: 139-44 (2009) 2009
|Regulation of estrogen rapid signaling through arginine methylation by PRMT1. |
Le Romancer, Muriel, et al.
Mol. Cell, 31: 212-21 (2008) 2008