Publications search

Found 37769 matches. Displaying 9211-9220
Bloom J, Cristea IM, Procko AL, Lubkov V, Chait BT, Snyder M, Cross FR
Show All Authors

Global Analysis of Cdc14 Phosphatase Reveals Diverse Roles in Mitotic Processes

JOURNAL OF BIOLOGICAL CHEMISTRY 2011 FEB 18; 286(7):5434-5445
Cdc14 phosphatase regulates multiple events during anaphase and is essential for mitotic exit in budding yeast. Cdc14 is regulated in both a spatial and temporal manner. It is sequestered in the nucleolus for most of the cell cycle by the nucleolar protein Net1 and is released into the nucleus and cytoplasm during anaphase. To identify novel binding partners of Cdc14, we used affinity purification of Cdc14 and mass spectrometric analysis of interacting proteins from strains in which Cdc14 localization or catalytic activity was altered. To alter Cdc14 localization, we used a strain deleted for NET1, which causes full release of Cdc14 from the nucleolus. To alter Cdc14 activity, we generated mutations in the active site of Cdc14 (C283S or D253A), which allow binding of substrates, but not dephosphorylation, by Cdc14. Using this strategy, we identified new interactors of Cdc14, including multiple proteins involved in mitotic events. A subset of these proteins displayed increased affinity for catalytically inactive mutants of Cdc14 compared with the wild-type version, suggesting they are likely substrates of Cdc14. We have also shown that several of the novel Cdc14-interacting proteins, including Kar9 (a protein that orients the mitotic spindle) and Bni1 and Bnr1 (formins that nucleate actin cables and may be important for actomyosin ring contraction) are specifically dephosphorylated by Cdc14 in vitro and in vivo. Our findings suggest the dephosphorylation of the formins may be important for their observed localization change during exit from mitosis and indicate that Cdc14 targets proteins involved in wide-ranging mitotic events.
Carlson KB, Singh P, Feaster MM, Ramnarain A, Pavlides C, Chen ZL, Yu WM, Feltri ML, Strickland S
Show All Authors

Mesenchymal Stem Cells Facilitate Axon Sorting, Myelination, and Functional Recovery in Paralyzed Mice Deficient in Schwann Cell-Derived Laminin

GLIA 2011 FEB; 59(2):267-277
Peripheral nerve function depends on a regulated process of axon and Schwann cell development. Schwann cells interact with peripheral neurons to sort and ensheath individual axons. Ablation of laminin gamma 1 in the peripheral nervous system (PNS) arrests Schwann cell development prior to radial sorting of axons. Peripheral nerves of laminin-deficient animals are disorganized and hypomyelinated. In this study, sciatic nerves of laminin-deficient mice were treated with syngenic murine adipose-derived stem cells (ADSCs). ADSCs expressed laminin in vitro and in vivo following transplant into mutant sciatic nerves. ADSC-treatment of mutant nerves caused endogenous Schwann cells to differentiate past the point of developmental arrest to sort and myelinate axons. This was shown by (1) functional, (2) ultrastructural, and (3) immunohistochemical analysis. Treatment of laminin-deficient nerves with either soluble laminin or the immortalized laminin-expressing cell line 3T3/L1 did not overcome endogenous Schwann cell developmental arrest. In summary, these results indicate that (1) laminin-deficient Schwann cells can be rescued, (2) a cell-based approach is beneficial in comparison with soluble protein treatment, and (3) mesenchymal stem cells modify sciatic nerve function via trophic effects rather than trans-differentiation in this system. (C) 2010 Wiley-Liss, Inc.
Ishii T, Mombaerts P
Show All Authors

Coordinated coexpression of two vomeronasal receptor V2R genes per neuron in the mouse

MOLECULAR AND CELLULAR NEUROSCIENCE 2011 FEB; 46(2):397-408
The detection of chemosensory stimuli by the sensory neurons of the mouse vomeronasal organ (VNO) is mainly mediated by seven-transmembrane receptors that are encoded by two large gene repertoires, V1R and V2R. The mouse genome contains 122 intact V2R genes, which can be grouped in four families by sequence homology: families A, B. and D (115 genes), and family C (7 genes). Vomeronasal sensory neurons (VSNs) in the basal layer of the VNO epithelium coexpress two V2R genes in non-random combinations: one family-ABD V2R gene together with one family-C V2R gene, such as Vmn2r1 (29% of basal VSNs) or Vmn2r2 (52%). This coordinated coexpression may contribute to the highly specialized sensory response profiles of VSNs, for instance by heterodimerization of a family-ABD with a family-C V2R. The mechanisms that regulate this coordinated cooexpression of two V2R genes per basal VSN are not understood. Among possible models are a sequential and dependent model of expression; a model of random combinations of expression followed by cellular selection of VSNs with appropriate combinations; and a model of direct coordination of gene expression by another gene family such as genes encoding transcription factors. Here, we describe two novel mouse strains with targeted mutations in the family-ABD V2R gene V2rf2 that begin to provide insight into this problem. We observe that the great majority of VSNs that express intact V2rf2 coexpress Vmn2r1 immunoreactivity, and that the percentage of Vmn2r1 coexpression increases from 3 to 10 wk. Having established this tight coexpression of V2rf2 with Vmn2r1, we then asked if it is maintained when the coding sequence of V2rf2 is deleted. We find that the number of VSNs expressing a locus with a targeted deletion in the coding sequence of V2rf2 that is likely a null mutation, is similar to the number of VSNs that express intact V2rf2. But 25% of these VSNs coexpress another family-ABD V2R, which is consistent with the absence of negative feedback from the mutated V2rf2 locus. Interestingly, 9.5% of VSNs expressing the targeted deletion of V2rf2 now coexpress Vmn2r2. Finally, the marginal region of the VNO epithelium, where immature VSNs are concentrated, has more RNA of family-ABD V2R genes than of family-C genes in postnatal wild-type mice. Our results are most consistent with the sequential and dependent model for the coordinated coexpression of two V2R genes per basal VSN. (C) 2010 Elsevier Inc. All rights reserved.
Anthony RM, Nimmerjahn F
Show All Authors

The role of differential IgG glycosylation in the interaction of antibodies with Fc gamma Rs in vivo

CURRENT OPINION IN ORGAN TRANSPLANTATION 2011 FEB; 16(1):7-14
Purpose of review Immunoglobulin G (IgG) antibodies are centrally involved in pathogen clearance, tissue destruction and inflammation during autoimmune diseases, and have emerged as an important mediator of chronic organ rejection. Besides these pro-inflammatory activities, IgG antibodies can also have anti-inflammatory activities and are used to treat autoimmune disease and to prevent organ rejection in the form of high-dose intravenous immunoglobulin (IVIg) therapy. This review summarizes the mechanisms involved in these diverse activities of IgG. Recent findings Recent studies have highlighted the role of cellular receptors recognizing the antibody constant fragment (Fc gamma-receptors, Fc gamma R) for mediating IgG-dependent effector functions. In addition, the IgG-attached sugar moiety was identified as a molecular switch shifting IgG activity from a pro-inflammatory to an anti-inflammatory pathway. Besides the family of canonical Fc gamma Rs, specific Icam-3 grabbing nonintegrin-related 1 (SIGN-R1) and DC-SIGN were identified to recognize IgG glycoforms rich in sialic acid. Summary The identification of the IgG-attached sugar moiety as an important modulator of IgG activity makes it an attractive target to selectively potentiate either the pro-inflammatory or the anti-inflammatory activities of IgG. This finding will provide optimized IgG-based therapeutics to either enhance IgG-dependent tumor cell destruction or suppress IgG-dependent autoimmunity and organ rejection.
Neff LM, Culiner J, Cunningham-Rundles S, Seidman C, Meehan D, Maturi J, Wittkowski KM, Levine B, Breslow JL
Show All Authors

Algal Docosahexaenoic Acid Affects Plasma Lipoprotein Particle Size Distribution in Overweight and Obese Adults

JOURNAL OF NUTRITION 2011 FEB; 141(2):207-213
Fish oils containing both EPA and DHA have been shown to have beneficial cardiovascular effects, but less is known about the independent effects of DHA. This study was designed to examine the effects of DHA on plasma lipid and lipoprotein concentrations and other biomarkers of cardiovascular risk in the absence of weight loss. In this randomized, controlled, double-blind trial, 36 overweight or obese adults were treated with 2 g/d of algal DHA or placebo for 4.5 mo. Markers of cardiovascular risk were assessed before and after treatment. In the DHA-supplemented group, the decrease in mean VLDL particle size (P <= 0.001) and increases in mean LDL (P <= 0.001) and HDL (P <= 0.001) particle sizes were significantly greater than changes in the placebo group. DHA supplementation also increased the concentrations of large LDL (P <= 0.001) and large HDL particles (P = 0.001) and decreased the concentrations of small LDL (P = 0.009) and medium HDL particles (P = 0.001). As calculated using NMR-derived data, DHA supplementation reduced VLDL TG (P = 0.009) and total TG concentrations (P = 0.006). Plasma IL-10 increased with DHA supplementation to a greater extent than placebo (P = 0.021), but no other significant changes were observed in glucose metabolism, insulin sensitivity, blood pressure, or markers of inflammation with DHA. In summary, DHA supplementation resulted in potentially beneficial changes in some., markers of cardiometabolic risk, whereas other markers were unchanged. J. Nutr. 141: 207-213, 2011.
Knepp AM, Grunbeck A, Banerjee S, Sakmar TP, Huber T
Show All Authors

Direct Measurement of Thermal Stability of Expressed CCR5 and Stabilization by Small Molecule Ligands

BIOCHEMISTRY 2011 FEB 1; 50(4):502-511
The inherent instability of heptahelical G protein-coupled receptors (GPCRs) during purification and reconstitution is a primary impediment to biophysical studies and to obtaining high-resolution crystal structures. New approaches to stabilizing receptors during purification and screening reconstitution procedures are needed. Here we report the development of a novel homogeneous time-resolved fluorescence assay (HTRF) to quantify properly folded CC-chemokine receptor 5 (CCR5). The assay permits high-throughput thermal stability measurements of femtomole quantities of CCR5 in detergent and in engineered nanoscale apolipoprotein-bound bilayer (NABB) particles. We show that recombinantly expressed CCR5 can be incorporated into NABB particles in high yield, resulting in greater thermal stability compared with that of CCR5 in a detergent solution. We also demonstrate that binding of CCR5 to the HIV-1 cellular entry inhibitors maraviroc, AD101, CMPD 167, and vicriviroc dramatically increases receptor stability. The HTRF assay technology reported here is applicable to other membrane proteins and could greatly facilitate structural studies of GPCRs.
Liu XY, Wang DL, Zhao Y, Tu B, Zheng ZX, Wang LN, Wang HY, Gu W, Roeder RG, Zhu WG
Show All Authors

Methyltransferase Set7/9 regulates p53 activity by interacting with Sirtuin 1 (SIRT1)

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA 2011 FEB 1; 108(5):1925-1930
Numerous studies indicate that Sirtuin 1 (SIRT1), a mammalian nicotinamide adenine dinucleotide (NAD(+))-dependent histone deacetylase (HDAC), plays a crucial role in p53-mediated stress responses by deacetylating p53. Nevertheless, the acetylation levels of p53 are dramatically increased upon DNA damage, and it is not well understood how the SIRT1-p53 interaction is regulated during the stress responses. Here, we identified Set7/9 as a unique regulator of SIRT1. SIRT1 interacts with Set7/9 both in vitro and in vivo. In response to DNA damage in human cells, the interaction between Set7/9 and SIRT1 is significantly enhanced and coincident with an increase in p53 acetylation levels. Importantly, the interaction of SIRT1 and p53 is strongly suppressed in the presence of Set7/9. Consequently, SIRT1-mediated deacetylation of p53 is abrogated by Set7/9, and p53-mediated transactivation is increased during the DNA damage response. Of note, whereas SIRT1 can be methylated at multiple sites within its N terminus by Set7/9, a methylation-defective mutant of SIRT1 still retains its ability to inhibit p53 activity. Taken together, our results reveal that Set7/9 is a critical regulator of the SIRT1-p53 interaction and suggest that Set7/9 can modulate p53 function indirectly in addition to acting through a methylation-dependent mechanism.
Callan-Jones A, Sorre B, Bassereau P
Show All Authors

Curvature-Driven Lipid Sorting in Biomembranes

COLD SPRING HARBOR PERSPECTIVES IN BIOLOGY 2011 FEB; 3(2):? Article a004648
It has often been suggested that the high curvature of transport intermediates in cells may be a sufficient means to segregate different lipid populations based on the relative energy costs of forming bent membranes. In this review, we present in vitro experiments that highlight the essential physics of lipid sorting at thermal equilibrium: It is driven by a trade-off between bending energy, mixing entropy, and interactions between species. We collect evidence that lipid sorting depends strongly on lipid-lipid and protein-lipid interactions, and hence on the underlying composition of the membrane and on the presence of bound proteins.
Wu XY, Shen QT, Oristian DS, Lu CP, Zheng QS, Wang HW, Fuchs E
Show All Authors

Skin Stem Cells Orchestrate Directional Migration by Regulating Microtubule-ACF7 Connections through GSK3 beta

CELL 2011 FEB 4; 144(3):341-352
Homeostasis and wound healing rely on stem cells (SCs) whose activity and directed migration are often governed by Wnt signaling. In dissecting how this pathway integrates with the necessary downstream cytoskeletal dynamics, we discovered that GSK3 beta, a kinase inhibited by Wnt signaling, directly phosphorylates ACF7, a > 500 kDa microtubule-actin crosslinking protein abundant in hair follicle stem cells (HF-SCs). We map ACF7's GSK3 beta sites to the microtubule-binding domain and show that phosphorylation uncouples ACF7 from microtubules. Phosphorylation-refractile ACF7 rescues overall microtubule architecture, but phosphorylation-constitutive mutants do not. Neither mutant rescues polarized movement, revealing that phospho-regulation must be dynamic. This circuitry is physiologically relevant and depends upon polarized GSK3 beta inhibition at the migrating front of SCs/progeny streaming from HFs during wound repair. Moreover, only ACF7 and not GSK beta-refractile-ACF7 restore polarized microtubule-growth and SC-migration to ACF7 null skin. Our findings provide insights into how this conserved spectraplakin integrates signaling, cytoskeletal dynamics, and polarized locomotion of somatic SCs.
Rosenberg BR, Hamilton CE, Mwangi MM, Dewell S, Papavasiliou FN
Show All Authors

Transcriptome-wide sequencing reveals numerous APOBEC1 mRNA-editing targets in transcript 3 ' UTRs

NATURE STRUCTURAL & MOLECULAR BIOLOGY 2011 FEB; 18(2):230-U300
Apolipoprotein B-editing enzyme, catalytic polypeptide-1 (APOBEC1) is a cytidine deaminase initially identified by its activity in converting a specific cytidine (C) to uridine (U) in apolipoprotein B (apoB) mRNA transcripts in the small intestine. Editing results in the translation of a truncated apoB isoform with distinct functions in lipid transport. To address the possibility that APOBEC1 edits additional mRNAs, we developed a transcriptome-wide comparative RNA sequencing (RNA-Seq) screen. We identified and validated 32 previously undescribed mRNA targets of APOBEC1 editing, all of which are located in AU-rich segments of transcript 3' untranslated regions (3' UTRs). Further analysis established several characteristic sequence features of editing targets, which were predictive for the identification of additional APOBEC1 substrates. The transcriptomics approach to RNA editing presented here dramatically expands the list of APOBEC1 mRNA editing targets and reveals a novel cellular mechanism for the modification of transcript 3' UTRs.