Página 12 dos resultados de 45945 itens digitais encontrados em 0.036 segundos
Resultados filtrados por Publicador: American Society for Biochemistry and Molecular Biology

‣ Revelation of p53-independent Function of MTA1 in DNA Damage Response via Modulation of the p21WAF1-Proliferating Cell Nuclear Antigen Pathway*

Li, Da-Qiang; Pakala, Suresh B.; Reddy, Sirigiri Divijendra Natha; Ohshiro, Kazufumi; Peng, Shao-Hua; Lian, Yi; Fu, Sidney W.; Kumar, Rakesh
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
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Although metastasis-associated protein 1 (MTA1), a component of the nucleosome remodeling and deacetylase (NuRD) complex, is a DNA-damage response protein and regulates p53-dependent DNA repair, it remains unknown whether MTA1 also participates in p53-independent DNA damage response. Here, we provide evidence that MTA1 is a p53-independent transcriptional corepressor of p21WAF1, and the underlying mechanism involves recruitment of MTA1-histone deacetylase 2 (HDAC2) complexes onto two selective regions of the p21WAF1 promoter. Accordingly, MTA1 depletion, despite its effect on p53 down-regulation, superinduces p21WAF1, increases p21WAF1 binding to proliferating cell nuclear antigen (PCNA), and decreases the nuclear accumulation of PCNA in response to ionizing radiation. In support of a p53-independent role of MTA1 in DNA damage response, we further demonstrate that induced expression of MTA1 in p53-null cells inhibits p21WAF1 promoter activity and p21WAF1 binding to PCNA. Consequently, MTA1 expression in p53-null cells results in increased induction of γH2AX foci and DNA double strand break repair, and decreased DNA damage sensitivity following ionizing radiation treatment. These findings uncover a new target of MTA1 and the existence of an additional p53-independent role of MTA1 in DNA damage response...

‣ Serine Residues in the Cytosolic Tail of the T-cell Antigen Receptor α-Chain Mediate Ubiquitination and Endoplasmic Reticulum-associated Degradation of the Unassembled Protein*

Ishikura, Shuhei; Weissman, Allan M.; Bonifacino, Juan S.
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
Português
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The T-cell antigen receptor (TCR) α-chain (TCRα) is a type I integral membrane protein that becomes ubiquitinated and targeted to the endoplasmic reticulum (ER)-associated degradation (ERAD) pathway when it fails to assemble into the heteromeric TCR complex. Remarkably, TCRα has a cytosolic tail of only five amino acid residues (i.e. RLWSS), none of which is the conventional ubiquitin acceptor, lysine. Herein we report that substitution of two conserved serine residues in the cytosolic tail of TCRα to alanine decreased ubiquitination, whereas placement of additional serine residues enhanced it. Moreover, replacement of the cytosolic serine residues by other ubiquitinatable residues (i.e. cysteine, threonine, or lysine) allowed ubiquitination to take place. Serine-dependent ubiquitination perfectly correlated with targeting of TCRα for ERAD. We also found that this ubiquitination was mediated by the ER-localized ubiquitin ligase, HRD1. These findings indicate that serine-dependent, HRD1-mediated ubiquitination targets TCRα to the ERAD pathway.

‣ Somatic Cell Plasticity and Niemann-Pick Type C2 Protein: ADIPOCYTE DIFFERENTIATION AND FUNCTION*

Csepeggi, Chad; Jiang, Min; Frolov, Andrey
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
Português
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The phenotypic stability of somatic cells is essential for the maintenance of both structural and functional organ integrity of the adult human body. Deregulated cell plasticity could result in the development of debilitating diseases such as cancer, fibrosis, atherosclerosis, obesity, and type 2 diabetes. We have previously demonstrated that a nonsense mutation in the NPC2 gene, which encodes ubiquitous, highly conserved, secretory protein with unknown function, leads to activation of human skin fibroblasts. The activated fibroblasts, also known as myofibroblasts, have the properties of mesenchymal stem cells and are able to differentiate along the mesodermal and endodermal lineages. Here we show that NPC2-null, but not the normal skin fibroblasts, possess characteristics of adipogenic progenitors as demonstrated by their specific gene expression pattern as well as the ability for efficient differentiation into white adipocytes. The presence of NPC2 in mature white adipocytes was also necessary for their maintenance because silencing NPC2 in differentiated cells by siRNA stimulated PPARG expression, which was followed by a shift toward a more favorable, brown adipocyte-like metabolic state characterized by up-regulated lipolysis and increased insulin sensitivity. It appears that NPC2 controls both the adipogenesis and the metabolic state of mature white adipocytes through a common mechanism that is linked to activation of FGFR2 that could be followed by induction of PPARG expression. Altogether...

‣ Production of Anti-carbohydrate Antibodies by Phage Display Technologies: POTENTIAL IMPAIRMENT OF CELL GROWTH AS A RESULT OF ENDOGENOUS EXPRESSION*

Yuasa, Noriyuki; Zhang, Wei; Goto, Tomohiro; Sakaue, Hiroyuki; Matsumoto-Takasaki, Ayano; Kimura, Miyo; Ohshima, Hiroya; Tsuchida, Yasunobu; Koizumi, Tomoyuki; Sakai, Keiko; Kojima, Takumi; Yamamoto, Kazuo; Nakata, Munehiro; Fujita-Yamaguchi, Yoko
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
Português
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Anti-mannotriose (Man3) antibodies were previously isolated from a Keio phage library displaying human single chain variable fragments (scFvs) using a neoglycolipid, Man3- dipalmitoylphosphatidylethanolamine. Of three genes constructed, the 5A3 clone was expressed in mouse myeloma NS0 cells as a conjugate with human IgG1 Fc (scFv-Fc) and characterized (Sakai, K., Shimizu, Y., Chiba, T., Matsumoto-Takasaki, A., Kusada, Y., Zhang, W., Nakata, M., Kojima, N., Toma, K., Takayanagi, A., Shimizu, N., and Fujita-Yamaguchi, Y. (2007) Biochemistry 46, 253–262; Zhang, W., Matsumoto-Takasaki, A., Kusada, Y., Sakaue, H., Sakai, K., Nakata, M., and Fujita-Yamaguchi, Y. (2007) Biochemistry 46, 263–270). Similarly, anti-Lex phages were screened from the same library with lacto-N-fucopentaose III (LNFPIII; Lex)-dipalmitoylphosphatidylethanolamine. Of five phage clones isolated, two scFv genes were constructed to express scFv-Fc proteins in NS0 cells. As was experienced with anti-Man3 scFv-Fc clones, only one anti-LNFPIII clone, 1F12, was successfully produced and purified as an scFv-Fc protein. Although anti-LNFPIII 1F12 and anti-Man3 5A3 scFv-Fc proteins were secreted into media, a decline in scFv-Fc production was observed with both stable clones during early passages. Transient expression of anti-LNFPIII and anti-Man3 scFv-Fc genes in COS-7 cells and subsequent analyses of scFv-Fc protein expression revealed accumulation of translated proteins in the endoplasmic reticulum for scFv-Fc proteins derived from clones that did not survive as stable clones. This report describes the following: (i) isolation of anti-LNFPIII scFv genes; (ii) purification of anti-LNFPIII scFv-Fc proteins from stably and transiently expressed cells; and (iii) extracellular or intracellular localization of two anti-LNFPIII and three anti-Man3 scFv-Fc proteins. The results suggest that expression of anti-Man3 and other anti-carbohydrate antibodies in mammalian cells is disadvantageous for cell growth.

‣ sFRP2 Suppression of Bone Morphogenic Protein (BMP) and Wnt Signaling Mediates Mesenchymal Stem Cell (MSC) Self-renewal Promoting Engraftment and Myocardial Repair*

Alfaro, Maria P.; Vincent, Alicia; Saraswati, Sarika; Thorne, Curtis A.; Hong, Charles C.; Lee, Ethan; Young, Pampee P.
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
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Transplantation of mesenchymal stem cells (MSCs) is a promising therapy for ischemic injury; however, inadequate survival of implanted cells in host tissue is a substantial impediment in the progress of cellular therapy. Secreted Frizzled-related protein 2 (sFRP2) has recently been highlighted as a key mediator of MSC-driven myocardial and wound repair. Notably, sFRP2 mediates significant enhancement of MSC engraftment in vivo. We hypothesized that sFRP2 improves MSC engraftment by modulating self-renewal through increasing stem cell survival and by inhibiting differentiation. In previous studies we demonstrated that sFRP2-expressing MSCs exhibited an increased proliferation rate. In the current study, we show that sFRP2 also decreased MSC apoptosis and inhibited both osteogenic and chondrogenic lineage commitment. sFRP2 activity occurred through the inhibition of both Wnt and bone morphogenic protein (BMP) signaling pathways. sFRP2-mediated inhibition of BMP signaling, as assessed by levels of pSMAD 1/5/8, was independent of its effects on the Wnt pathway. We further hypothesized that sFRP2 inhibition of MSC lineage commitment may reduce heterotopic osteogenic differentiation within the injured myocardium, a reported adverse side effect. Indeed...

‣ Sp1-dependent Activation of HDAC7 Is Required for Platelet-derived Growth Factor-BB-induced Smooth Muscle Cell Differentiation from Stem Cells*

Zhang, Li; Jin, Min; Margariti, Andriana; Wang, Gang; Luo, Zhenling; Zampetaki, Anna; Zeng, Lingfang; Ye, Shu; Zhu, Jianhua; Xiao, Qingzhong
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
Português
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We have previously demonstrated that histone deacetylase 7 (HDAC7) expression and splicing play an important role in smooth muscle cell (SMC) differentiation from embryonic stem (ES) cells, but the molecular mechanisms of increased HDAC7 expression during SMC differentiation are currently unknown. In this study, we found that platelet-derived growth factor-BB (PDGF-BB) induced a 3-fold increase in the transcripts of HDAC7 in differentiating ES cells. Importantly, our data also revealed that PDGF-BB regulated HDAC7 expression not through phosphorylation of HDAC7 but through transcriptional activation. By dissecting its promoters with progressive deletion analysis, we identified the sequence between −343 and −292 bp in the 5′-flanking region of the Hdac7 gene promoter as the minimal PDGF-BB-responsive element, which contains one binding site for the transcription factor, specificity protein 1 (Sp1). Mutation of the Sp1 site within this PDGF-BB-responsive element abolished PDGF-BB-induced HDAC7 activity. PDGF-BB treatment enhanced Sp1 binding to the Hdac7 promoter in differentiated SMCs in vivo as demonstrated by the chromatin immunoprecipitation assay. Moreover, we also demonstrated that knockdown of Sp1 abrogated PDGF-BB-induced HDAC7 up-regulation and SMC differentiation gene expression in differentiating ES cells...

‣ Integrin α1β1 Promotes Caveolin-1 Dephosphorylation by Activating T Cell Protein-tyrosine Phosphatase*

Borza, Corina M.; Chen, Xiwu; Mathew, Sijo; Mont, Stacey; Sanders, Charles R.; Zent, Roy; Pozzi, Ambra
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
Português
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Integrin α1β1 is a collagen receptor that down-regulates collagen and reactive oxygen species (ROS) production, and mice lacking this receptor show increased ROS levels and exacerbated glomerular sclerosis following injury. Caveolin-1 (Cav-1) is a multifunctional protein that is tyrosine-phosphorylated in response to injury and has been implicated in ROS-mediated injury. Cav-1 interacts with integrins, and integrin α1β1 binds/activates T cell protein-tyrosine phosphatase (TCPTP), which is homologous to the tyrosine phosphatase PTP1B known to dephosphorylate Cav-1. In this study, we analyzed whether phosphorylated Cav-1 (pCav-1) is a substrate of TCPTP and if integrin α1β1 is essential for promoting TCPTP-mediated Cav-1 dephosphorylation. We found that Cav-1 phosphorylation is significantly higher in cells lacking integrin α1β1 at base line and following oxidative stress. Overexpression of TCPTP leads to reduced pCav-1 levels only in cells expressing integrin α1β1. Using solid phase binding assays, we demonstrated that 1) purified Cav-1 directly interacts with TCPTP and the integrin α1 subunit, 2) pCav-1 is a substrate of TCPTP, and 3) TCPTP-mediated Cav-1 dephosphorylation is highly increased by the addition of purified integrin α1β1 or an integrin α1 cytoplasmic peptide to which TCPTP has been shown to bind. Thus...

‣ Vascular Smooth Muscle Notch Signals Regulate Endothelial Cell Sensitivity to Angiogenic Stimulation*

Yang, Ke; Proweller, Aaron
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
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The evolutionarily conserved Notch signaling pathway is required for normal vascular development and function, and genetic associations link select Notch receptors and ligands to human clinical syndromes featuring blood vessel abnormalities and stroke susceptibility. A previously described mouse model engineered to suppress canonical Notch signaling in vascular smooth muscle cells (vSMCs) revealed surprising anatomical defects in arterial patterning and vessel maturation, suggesting that vSMCs have the functional capacity to influence blood vessel formation in a Notch signaling-dependent manner. In further analyses using this model system, we now show that explanted aortic ring tissue and Matrigel implants from the smooth muscle Notch signaling-deficient mice yield markedly diminished responses to angiogenic stimuli. Furthermore, cultured Notch signaling-deficient primary vSMCs have reduced proliferation and migration capacities and reveal diminished expression of PDGF receptor β and JAGGED1 ligand. These observations prompted a series of endothelial cell (EC)-vSMC co-culture experiments that revealed a requirement for intact vSMC Notch signals via JAGGED1 for efficient EC Notch1 receptor activation and EC proliferation. Taken together...

‣ Endothelial Krüppel-like Factor 4 Regulates Angiogenesis and the Notch Signaling Pathway*

Hale, Andrew T.; Tian, Hongmei; Anih, Ejike; Recio, Fernando O.; Shatat, Mohammad A.; Johnson, Trent; Liao, Xudong; Ramirez-Bergeron, Diana L.; Proweller, Aaron; Ishikawa, Masakazu; Hamik, Anne
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
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Background: The transcription factor Krüppel-like factor 4 (KLF4) is a critical regulator of endothelial cell biology.

‣ Characterization of the Stability and Bio-functionality of Tethered Proteins on Bioengineered Scaffolds: IMPLICATIONS FOR STEM CELL BIOLOGY AND TISSUE REPAIR*

Wang, Ting-Yi; Bruggeman, Kiara A. F.; Sheean, Rebecca K.; Turner, Bradley J.; Nisbet, David R.; Parish, Clare L.
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
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Background: Tethering proteins onto bioengineered scaffolds enables longterm delivery, however protein stability, release kinetics, and functionality over time remains unknown.

‣ Tracking the Subcellular Fate of 20(S)-Hydroxycholesterol with Click Chemistry Reveals a Transport Pathway to the Golgi*

Peyrot, Sara M.; Nachtergaele, Sigrid; Luchetti, Giovanni; Mydock-McGrane, Laurel K.; Fujiwara, Hideji; Scherrer, David; Jallouk, Andrew; Schlesinger, Paul H.; Ory, Daniel S.; Covey, Douglas F.; Rohatgi, Rajat
Fonte: American Society for Biochemistry and Molecular Biology Publicador: American Society for Biochemistry and Molecular Biology
Tipo: Artigo de Revista Científica
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Background: Oxysterols are a class of emerging signaling molecules whose cell biology is poorly understood.