5,297 research outputs found
Fc receptor-mediated phagocytosis occurs in macrophages at exceedingly low cytosolic Ca2+ levels
No full textAbstract
Cytosolic free Ca2+ ([Ca2+]i) homeostasis was investigated in mouse peritoneal macrophages and in the macrophage-like cell line J774. [Ca2+]i measurements were performed in both cells in suspension and cells in monolayers loaded with either quin2 or fura-2. Resting [Ca2+]i was 110-140 and 85-120 nM for cell suspensions and monolayers, respectively. There were no significant differences in [Ca2+]i between the two macrophage populations whether quin2 or fura-2 were used as Ca2+ indicators. Addition of heat-aggregated IgG, IgG-coated erythrocyte ghosts, or a rat monoclonal antibody (2.4G2) directed against mouse Fc receptor II induced a rise in [Ca2+]i. This [Ca2+]i increase was consistently observed in J774 and peritoneal macrophage suspensions and in J774 macrophage monolayers; in contrast it was observed inconsistently in peritoneal macrophages in monolayer cultures. The increase in [Ca2+]i induced by ligation of Fc receptors was inhibited totally in macrophages in suspension and by 80% in macrophages in monolayers by a short preincubation of macrophages with PMA; however, phagocytosis itself was unaffected. The effect of reducing cytosolic Ca2+ to very low concentrations on Fc receptor-mediated phagocytosis was also investigated. By incubating macrophages with high concentrations of quin2/AM in the absence of extracellular Ca2+, or by loading EGTA into the cytoplasm, the [Ca2+]i was buffered and clamped to 1-10 nM. Despite this, the phagocytosis of IgG-coated erythrocytes proceeded normally. These observations confirm the report of Young et al. (Young, J. D., S. S. Ko, and Z. A. Cohn. 1984. Proc. Natl. Acad. Sci. USA. 81:5430-5434) that ligation of Fc receptors causes Ca2+ mobilization in macrophages. However, these results confirm and extend the findings of McNeil et al. (McNeil, P. L., J. A. Swanson, S. D. Wright, S. C. Silverstein, and D. L. Taylor. 1986. J. Cell Biol. 102:1586-1592) that a rise in [Ca2+]i is not required for Fc receptor-mediated phagocytosis; and they provide direct evidence that Fc receptor-mediated phagocytosis occurs normally even at exceedingly low [Ca2+]i
Woody's Children, August 28, 1976
No full textThis episode of Woody's Children is a repeat of a program focusing on American poet, author, and singer-songwriter Shel Silverstein, but with new material added. Woody's Children was a radio show that aired on WQXR in New York City. Hosted by Robert Sherman, the program featured interviews with notable American and European folk musicians, unique live performances, and Sherman's insightful commentary
Ca2+-independent F-actin assembly and disassembly during Fc receptor-mediated phagocytosis in mouse macrophages
No full textAbstract
Phagocytosis of IgG-coated particles by macrophages is presumed to involve the actin-based cytoskeleton since F-actin accumulates beneath forming phagosomes, and particle engulfment is blocked by cytochalasins, drugs that inhibit actin filament assembly. However, it is unknown whether Fc receptor ligation affects the rate or extent of F-actin assembly during phagocytosis of IgG-coated particles. To examine this question we have used a quantitative spectrofluorometric method to examine F-actin dynamics during a synchronous wave of phagocytosis of IgG-coated red blood cells by inflammatory mouse macrophages. We observed a biphasic rise in macrophage F-actin content during particle engulfment, with maxima at 1 and 5 min after the initiation of phagocytosis. F-actin declined to resting levels by 30 min, by which time particle engulfment was completed. These quantitative increases in macrophage F-actin were reflected in localized changes in F-actin distribution. Previous work showed that the number of IgG-coated particles engulfed by macrophages is unaffected by buffering extracellular calcium or by clamping cytosolic free calcium concentration ([Ca2+]i) to very low levels (Di Virgilio, F., B. C. Meyer, S. Greenberg, and S. C. Silverstein. 1988. J. Cell Biol. 106: 657-666). To determine whether clamping [Ca2+]i in macrophages affects the rate of particle engulfment, or the assembly or disassembly of F-actin during phagocytosis, we examined these parameters in macrophages whose [Ca2+]i had been clamped to approximately less than 3 nM with fura 2/AM and acetoxymethyl ester of EGTA. We found that the initial rate of phagocytosis, and the quantities of F-actin assembled and disassembled were similar in Ca(2+)-replete and Ca(2+)-depleted macrophages. We conclude that Fc receptor-mediated phagocytosis in mouse macrophages is accompanied by an ordered sequence of assembly and disassembly of F-actin that is insensitive to [Ca2+]i
Recommended from our members
Amy Silverstein Discusses Her Experiences with Two Heart Transplants
No full textJennifer Cohen interviews Amy Silverstein, attorney, speaker, and award-winning author of Sick Girl, a book also serialized by U.S. News and World Report. Her new book, My Glory Was I Had Such Friends highlights the support she had in her move across the country for her second heart transplant. Apple will be streaming Silverstein’s limited
Chronicle (Paterson, NJ), Vol. 23, No. 35, Sept 23, 1951
No full textLocal information pertaining to Paterson, N.J. and surrounding Passaic County. Issues may include events, government, business, political cartoons, engagement and marriage announcements, and birth announcements. This publication was also known as the Paterson Chronicle (1952) and the Paterson Sunday Chronicle (1951-1952)
Tyrosine phosphorylation is required for Fc receptor-mediated phagocytosis in mouse macrophages
No full textAlthough Fc receptor-mediated phagocytosis is accompanied by a variety of transmembrane signaling events, not all signaling events are required for particle ingestion. For example, Fc receptor-mediated phagocytosis in mouse inflammatory macrophages (Di Virgilio, F., B. C. Meyer, S. Greenberg, and S. C. Silverstein. 1988. J. Cell Biol. 106:657; Greenberg, S., J. El Khoury, F. Di Virgilio, and S. C. Silverstein. 1991. J. Cell Biol. 113:757) and neutrophils (Della Bianca, V., M. Grzeskowiak, and F. Rossi. 1990. J. Immunol. 144:1411) occurs in the absence of cytosolic calcium transients. We sought to identify transmembrane signaling events that are essential for phagocytosis. Here we show that tyrosine phosphorylation is an early event after Fc receptor ligation in mouse inflammatory macrophages, and that the formation of tyrosine phosphoproteins coincides temporally with the appearance of F-actin beneath phagocytic cups. The distribution of tyrosine phosphoproteins that accumulated beneath phagocytic cups was punctate and corresponded to areas of high ligand density on the surface of the antibody-coated red blood cells, which provided the phagocytic stimulus. A tyrosine kinase inhibitor, genistein, but not several inhibitors of protein kinase C, blocked the appearance of tyrosine phosphoproteins as assessed by immunofluorescence, the focal accumulation of F-actin beneath immunoglobulin G-opsonized particles, and the ingestion of these particles as well. We suggest that tyrosine phosphorylation is a critical signaling event that underlies Fc receptor-mediated phagocytosis in mouse macrophages, and is necessary for the engulfment per se
Law's Allure in American Politics and Policy: What It Is, What It Is Not, and What It Might Yet Be
No full textResponding to a set of review essays, the author of Law's Allure: How Law Shapes, Constrains, Saves, and Kills Politics (Silverstein 2009) argues that politicians and policy entrepreneurs fail to calculate the risks of juridification—the judicialization of policy combined with the legalization of politics itself—which have expanded and accelerated in the United States in recent decades. Paradigmatic case studies (on subjects including poverty, electoral districting, automated budgeting, war powers, abortion laws, and the regulation of tobacco as well as the environment) illustrate the risks of various patterns of juridification and construct an agenda for future research.</jats:p
Histone deacetylases and their co-regulators in Schizosaccharomyces pombe
No full textThe DNA in every eukaryotic cell is wrapped around eight core histones to form the nucleosome. Therefore all events that involve DNA must also involve chromatin and nucleosomes. By regulating chromatin structure the cell can regulate the reactivity of the DNA. One of the most common ways of altering nucleosomes is the acetylation of lysine residues. Two enzymes are required to maintain the correct equilibrium for optimal cell growth: histone acetyltransferases (HATs) and histone deacetyltransferases (HDACs). In general, histone hypoacetylation is correlated with transcriptional inactivation, while hyperacetylation is correlated with active gene transcription.In Schizosaccharomyces pombe, mating type loci are silenced. Deletion of HDAC Hos2 had previously been shown to slightly increase silencing at the mating type locus. To assess whether any other HDAC was necessary for mating type silencing, cells were treated with HDAC poison Trichostatin A (TSA). TSA was found to cause a mild derepression of the mating type locus, indicating that another HDAC was responsible for silencing in this region. The RNA interference nuclease Dcr1 was later identified, and showed to degrade double stranded RNA into small nucleotide fragments. Deletion of dcr1 caused chromosome segregation defects and derepression of centromeric silencing.Rpd3 in S. cerevisiae is recruited to genomic targets by interacting with co-regulator Sin3. S. pombe has three Sin3 homologs. Pst1 interacts with the HDAC Clr6, and like Clr6 is an essential gene, mutants of which display chromosome mis-segregation and derepression of centromeric silencing. Pst1 was required for centromeric cohesion, and localized to centromeres in late S phase. Thus a co-repressor paradigm could be applied to centromere silencing as well. A comparative characterization of HDACs in S. pombe showed that the HDACs had different localizations and histone specificities.The comparison of HDACs was taken further with a genome wide expression analysis and histone density study of mutants. Results indicated that Clr6 was most often involved in promoter initiated gene repression, whereas Hos2 promoted the high expression of growth related genes by deacetylating H4K16ac in their coding regions. A class II HDAC, Clr3, was found to act cooperatively with Sir2 throughout the genome. Using a genomic approach to analyze Pst3, it was established that Clr6 and Pst3 could cooperate to negatively regulate genes by binding to their promoter regions. On the other hand, Pst3 was also involved in the up-regulation of ribosome biosynthesis genes, and could bind to the rDNA.List of scientific papersI. Olsson TG, Silverstein RA, Ekwall K, Sunnerhagen P (1999). "Transient inhibition of histone deacetylase activity overcomes silencing in the mating-type region in fission yeast." Curr Genet 35(2): 82-7 https://pubmed.ncbi.nlm.nih.gov/10079326II. Provost P, Silverstein RA, Dishart D, Walfridsson J, Djupedal I, Kniola B, Wright A, Samuelsson B, Radmark O, Ekwall K (2002). "Dicer is required for chromosome segregation and gene silencing in fission yeast cells." Proc Natl Acad Sci U S A 99(26): 16648-53. Epub 2002 Dec 13 https://pubmed.ncbi.nlm.nih.gov/12482946III. Silverstein RA, Richardson W, Levin H, Allshire R, Ekwall K (2003). "A new role for the transcriptional corepressor SIN3; regulation of centromeres." Curr Biol 13(1): 68-72 https://pubmed.ncbi.nlm.nih.gov/12526748IV. Bjerling P, Silverstein RA, Thon G, Caudy A, Grewal S, Ekwall K (2002). "Functional divergence between histone deacetylases in fission yeast by distinct cellular localization and in vivo specificity." Mol Cell Biol 22(7): 2170-81 https://pubmed.ncbi.nlm.nih.gov/11884604V. Wiren M, Silverstein RA, Sinha I, Walfridsson J, Lee HM, Laurenson P, Pillus L, Robyr D, Grunstein M, Ekwall K (2005). "Genomewide analysis of nucleosome density histone acetylation and HDAC function in fission yeast." EMBO J 24(16): 2906-18. Epub 2005 Aug 4 https://pubmed.ncbi.nlm.nih.gov/16079916VI. Silverstein RA, Walfridsson J, Bonilla C, Ekwall K (2007). "Sin3 homolog Pst3 a key factor in nucleolar function." Current Biology (Submitted)</p
DS_10.1177_2380084419861384 – Supplemental material for Dental Professionals’ Engagement in Tobacco, Electronic Cigarette, and Cannabis Patient Counseling
No full textSupplemental material, DS_10.1177_2380084419861384 for Dental Professionals’ Engagement in Tobacco, Electronic Cigarette, and Cannabis Patient Counseling by B.W. Chaffee, J. Urata, E.T. Couch and S. Silverstein in JDR Clinical & Translational Research</p
Extracellular nucleotides mediate Ca2+ fluxes in J774 macrophages by two distinct mechanisms
No full textWe have studied the effects of extracellular nucleotides on the cytosolic free calcium concentration [( Ca2+]i) in J774 macrophages using quin2 and indo-1 as indicator dyes. Micromolar quantities of ATP induced a biphasic increase in [Ca2+]i: a rapid and transient increase (peak I) which was due to mobilization of Ca2+ from intracellular stores and a second more sustained elevation (peak II) due to influx of extracellular Ca2+. The sustained peak II elevation had two components, a "low threshold" (1 microM ATP) response which saturated at 10-50 microM ATP and a "high threshold" response, apparent at [ATP] greater than 100 microM. The latter component was not seen with nucleotides other than ATP and correlated with an ATP-induced generalized increase in plasma membrane permeability. A variant J774 cell line was isolated which does not demonstrate this ATP-induced increase in plasma membrane permeability; nevertheless, it demonstrated both the release of Ca2+ from intracellular stores and the low threshold component of the Ca2+ influx across the plasma membrane in response to nucleoside di- and triphosphates. Several lines of evidence indicate that the fully ionized (i.e. free acid) forms of nucleoside di- and triphosphates were the ligands that mediated these increases in [Ca2+]i. These data show that extracellular nucleotides mediate Ca2+ fluxes by two distinct mechanisms in J774 cells. In one, the rise in [Ca2+]i is due to release of Ca2+ from intracellular stores and Ca2+ influx across the plasma membrane. This response is elicited preferentially by the free acid forms of purine and pyrimidine nucleoside di- and triphosphates. In the other, the rise in [Ca2+]i reflects a more generalized increase in plasma membrane permeability and is elicited by ATP4- only
- …
