1,721,018 research outputs found
Cross talk among calcineurin, Sp1/Sp3, and NFAT in control of p21(WAF1/CIP1) expression in keratinocyte differentiation.
No full textThe Molecular Basis of Notch Signaling Regulation: A Complex Simplicity
No full textThe Notch receptors have attracted considerable attention for their ability to control cellular functions that regulate embryo development and tissue homeostasis. Notch receptors act by controlling the expression of a specific set of target genes. If Notch signaling system can be so simple, and yet so complex in its pleiotropic effects, then a sophisticated network of regulatory mechanisms is required to maintain the control over the initiation, activity and termination of this signaling pathway. A multitude of regulatory mechanisms has been discovered that controls the interaction of Notch receptors with their ligands, the assembling of a Notch transcriptional activation complex and the termination of Notch signals. The intracellular and extracellular domains of the Notch receptors are synthesized as single proteins, pairing with each other during their trafficking through the exocytotic route. The mechanisms operating in the phase preceding the generation of the heterodimeric signal-competent Notch receptors can be as elaborate and physiologically important as those operating downstream of Notch receptor activation. These regulatory mechanisms, which are essential to understand the role of Notch signaling in human physiology and pathology are reviewed here.The Notch receptors have attracted considerable attention for their ability to control cellular functions that regulate embryo development and tissue homeostasis. Notch receptors act by controlling the expression of a specific set of target genes. If Notch signaling system can be so simple, and yet so complex in its pleiotropic effects, then a sophisticated network of regulatory mechanisms is required to maintain the control over the initiation, activity and termination of this signaling pathway. A multitude of regulatory mechanisms has been discovered that controls the interaction of Notch receptors with their ligands, the assembling of a Notch transcriptional activation complex and the termination of Notch signals. The intracellular and extracellular domains of the Notch receptors are synthesized as single proteins, pairing with each other during their trafficking through the exocytotic route. The mechanisms operating in the phase preceding the generation of the heterodimeric signal
Role of a white collar-1-white collar-2 complex in blue-light signal transduction
No full textMutations in either white collar-1 (wc-1) or white collar-2 (wc-2) lead to a loss of most blue-light-induced phenomena in Neurospora crassa. Sequence analysis and in vitro experiments show that WC-1 and WC-2 are transcription factors regulating the expression of light-induced genes. The WC proteins form homo- and heterodimers in vitro; this interaction could represent a fundamental step in the control of their activity. We demonstrate in vivo that the WC proteins are assembled in a white collar complex (WCC) and that WC-1 undergoes a change in mobility due to light-induced phosphorylation events. The phosphorylation level increases progressively upon light exposure, producing a hyperphosphorylated form that is degraded and apparently replaced in the complex by a newly synthesized WC-1, WC-2 is unmodified and also does not change quantitatively in the time frame examined. Light-dependent phosphorylation of WC-1 also occurs in a wc-2 mutant, suggesting that a functional WC-2 is dispensable for this light-specific event. These results suggest that light-induced phosphorylation and degradation of WC-1 could play a role in the transient expression of blue-light-regulated genes. Our findings suggest a mechanism by which WC-1 and WC-2 mediate light responses in Neurospora
The Translation Factor eIF6 Is a Notch-Dependent Regulator of Cell Migration and Invasion
No full textA growing body of evidence indicates that protein factors controlling translation play an important role in tumorigenesis. The protein known as eIF6 is a ribosome anti-association factor that has been implicated in translational initiation and in ribosome synthesis. Over-expression of eIF6 is observed in many natural tumours, and causes developmental and differentiation defects in certain animal models. Here we show that the transcription of the gene encoding eIF6 is modulated by the receptor Notch-1, a protein involved in embryonic development and cell differentiation, as well as in many neoplasms. Inhibition of Notch-1 signalling by gamma-secretase inhibitors slowed down cell-cycle progression and reduced the amount of eIF6 in lymphoblastoid and ovarian cancer cell lines. Cultured ovarian cancer cell lines engineered to stably over-expressing eIF6 did not show significant changes in proliferation rate, but displayed an enhanced motility and invasive capacity. Inhibition of Notch-1 signalling in the cells over-expressing eIF6 was effective in slowing down the cell cycle, but did not reduce cell migration and invasion. On the whole, the results suggest that eIF6 is one of the downstream effectors of Notch-1 in the pathway that controls cell motility and invasiveness
Yeast-Based Screen to Identify Natural Compounds with a Potential Therapeutic Effect in Hailey-Hailey Disease
Full text linkThe term orthodisease defines human disorders in which the pathogenic gene has orthologs in model organism genomes. Yeasts have been instrumental for gaining insights into the molecular basis of many human disorders, particularly those resulting from impaired cellular metabolism. We and others have used yeasts as a model system to study the molecular basis of Hailey-Hailey disease (HHD), a human blistering skin disorder caused by haploinsufficiency of the gene ATP2C1 the orthologous of the yeast gene PMR1. We observed that K. lactis cells defective for PMR1 gene share several biological similarities with HHD derived keratinocytes. Based on the conservation of ATP2C1/PMR1 function from yeast to human, here we used a yeast-based assay to screen for molecules able to influence the pleiotropy associated with PMR1 deletion. We identified six compounds, Kaempferol, Indirubin, Lappaconite, Cyclocytidine, Azomycin and Nalidixic Acid that induced different major shape phenotypes in K. lactis. These include mitochondrial and the cell-wall morphology-related phenotypes. Interestingly, a secondary assay in mammalian cells confirmed activity for Kaempferol. Indeed, this compound was also active on human keratinocytes depleted of ATP2C1 function by siRNA-treatment used as an in-vitro model of HHD. We found that Kaempferol was a potent NRF2 regulator, strongly inducing its expression and its downstream target NQO1. In addition, Kaempferol could decrease oxidative stress of ATP2C1 defective keratinocytes, characterized by reduced NRF2-expression. Our results indicated that the activation of these pathways might provide protection to the HHD-skin cells. As oxidative stress plays pivotal roles in promoting the skin lesions of Hailey-Hailey, the NRF2 pathway could be a viable therapeutic target for HHD
“White Collar 1, a central regulator of blue light response in Neurospora, is a Zinc finger protein”
Full text linkThe Neurospora crassa blind mutant white collar-1 (wc-1) is pleiotropically defective in all blue light-induced phenomena, establishing a role for the wc-1 gene product in the signal transduction pathway. We report the cloning of the wc-1 gene isolated by chromosome walking and mutant complementation. The elucidation of the wc-1 gene product provides a key piece of the blue light signal transduction puzzle. The wc-1 gene encodes a 125 kDa protein whose encoded motifs include a single class four, zinc finger DNA binding domain and a glutamine-rich putative transcription activation domain. We demonstrate that the wc-1 zinc finger domain, expressed in Escherichia coli, is able to bind specifically to the promoter of a blue light-regulated gene of Neurospora using an in vitro gel retardation assay. Furthermore, we show that wc-1 gene expression is autoregulated and is transcriptionally induced by blue light irradiation.The Neurospora crassa blind mutant white collar-1 (wc-1) is pleiotropically defective in all blue light-induced phenomena, establishing a role for the wc-1 gene product in the signal transduction pathway. We report the cloning of the wc-1 gene isolated by chromosome walking and mutant complementation. The elucidation of the wc-1 gene product provides a key piece of the blue light signal transduction puzzle. The wc-1 gene encodes a 125 kDa protein whose encoded motifs include a single class four, zinc finger DNA binding domain and a glutamine-rich putative transcription activation domain. We demonstrate that the wc-1 zinc finger domain, expressed in Escherichia coli, is able to bind specifically to the promoter of a blue light-regulated gene of Neurospora using an in vitro gel retardation assay. Furthermore, we show that wc-1 gene expression is autoregulated and is transcriptionally induced by blue light irradiation
Efficacy of the melanocortin analogue Nle4-D-Phe7-α-melanocyte-stimulating hormone in the treatment of patients with Hailey-Hailey disease
No full textBackgroundHailey-Hailey disease (HHD) is a rare, chronic and recurrent blistering disorder, which is characterized clinically by erosions occurring primarily in intertriginous regions, and histologically by suprabasal acantholysis. Oxidative stress plays a specific role in the pathogenesis of HHD, by regulating the expression of factors playing an important role in keratinocyte proliferation and differentiation. AimGiven the significance of oxidative stress in HHD, we investigated the potential effects of the antioxidant properties of an -MSH analogue, Nle4-D-Phe7--MSH (afamelanotide), in HHD lesion-derived keratinocytes. ResultsTreatment of HHD-derived keratinocytes with afamelanotide contributed to upregulation of Nrf2 [nuclear factor (erythroid-derived 2)-like 2], a redox-sensitive transcription factor that plays a pivotal role in redox homeostasis during oxidative stress. Additionally, afamelanotide treatment restored the defective proliferative capability of lesion-derived keratinocytes. Our results show that Nrf2 is an important target of the afamelanotide signalling that reduces oxidative stress. Because afamelanotide possesses antioxidant effects, we also assessed the clinical potential of this -MSH analogue in the treatment of patients with HHD. In a phase II open-label pilot study, afamelanotide 16mg was administered subcutaneously as a sustained-release resorbable implant formulation to two patients with HHD, who had a number of long-standing skin lesions. For both patients, their scores on the Short Form-36 improved 30days after the first injection of afamelanotide, and both had 100% clearance of HHD lesions 60days after the first injection, independently of the lesion location. ConclusionsAfamelanotide is effective for the treatment of skin lesions in HHD
Regulation of proapoptotic proteins Bak1 and p53 by miR-125b in an experimental model of Alzheimer's disease: Protective role of 17β-estradiol
No full textAlzheimer's disease has become one of the most impacting disorders since world population is rapidly aging. MicroRNA-125b plays a crucial role in many cellular processes and pathologies, but, to date, its role in Alzheimer's disease is controversial. In this study, we demonstrated, for the first time, that the down regulation of miR-125b is a key event for the neurotoxic effect of Aβ treatment in cortical neurons. Moreover, we found that 17β-estradiol treatment protects neurons from the Aβ-peptide induced neurotoxicity by increasing miR-125b expression that, in turn, decreased the expression, both at gene and protein levels, of the pro-apoptopic proteins Bak1 and p53. Overall, our data reveal miR-125b as a novel neuro-protector miRNA in Alzheimer's disease
Specific down-modulation of Notch1 signaling in cervical cancer cells is required for sustained HPV-E6/E7 expression and late steps of malignant transformation
No full textThe Notch family of cell surface receptors plays a key role in cell-fate determination and differentiation, functioning in a cell- and context-specific manner. In mammalian cells, Notch activation is generally thought to maintain stem cell potential and inhibit differentiation, thereby promoting carcinogenesis. However, in other contexts such as primary epithelial cells (keratinocytes), increased Notch activity causes exit from the cell cycle and/or commitment to differentiation. We now report that expression of the endogenous Notch1 gene is markedly reduced in a panel of cervical carcinoma cells whereas expression of Notch2 remains elevated, and Notch1 expression is similarly reduced or absent in invasive cervical cancers. Conversely, expression of activated Notch1 causes strong growth inhibition of HPV-positive, but not HPV-negative, cervical carcinoma cells, but exerts no such effects on other epithelial tumor cells. Increased Notch1 signaling, but not Notch2, causes a dramatic down-modulation of HPV-driven transcription of the E6/E7 viral genes, through suppression of AP-1 activity by up-regulation of the Fra-1 family member and decreased c-Fos expression. Thus, Notch1 exerts specific protective effects against HPV-induced transformation through suppression of E6/E7 expression, and down-modulation of Notch1 expression is likely to play an important role in late stages of HPV-induced carcinogenesis
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