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Articles 91 - 98 of 98

Full-Text Articles in Microbiology

Involvement Of Raft-Like Plasma Membrane Domains Of Entamoeba Histolytica In Pinocytosis And Adhesion, Richard C. Laughlin, Glen C. Mcgugan, Rhonda R. Powell, Brenda H. Welter, Lesly A. Temesvari Sep 2004

Involvement Of Raft-Like Plasma Membrane Domains Of Entamoeba Histolytica In Pinocytosis And Adhesion, Richard C. Laughlin, Glen C. Mcgugan, Rhonda R. Powell, Brenda H. Welter, Lesly A. Temesvari

Publications

Lipid rafts are highly ordered, cholesterol-rich, and detergent-resistant microdomains found in the plasma membrane of many eukaryotic cells. These domains play important roles in endocytosis, secretion, and adhesion in a variety of cell types. The parasitic protozoan Entamoeba histolytica, the causative agent of amoebic dysentery, was determined to have raft-like plasma membrane domains by use of fluorescent lipid analogs that specifically partition into raft and nonraft regions of the membrane. Disruption of raft-like membrane domains in Entamoeba with the cholesterol-binding agents filipin and methyl-β-cyclodextrin resulted in the inhibition of several important virulence functions, fluid-phase pinocytosis, and adhesion to host …


The Wasp-Like Protein Scar Regulates Macropinocytosis, Phagocytosis And Endosomal Membrane Flow In Dictyostelium, David J. Seastone, Ed Harris, Lesly A. Temesvari, James E. Bear, Charles L. Saxe, James Cardelli Jul 2001

The Wasp-Like Protein Scar Regulates Macropinocytosis, Phagocytosis And Endosomal Membrane Flow In Dictyostelium, David J. Seastone, Ed Harris, Lesly A. Temesvari, James E. Bear, Charles L. Saxe, James Cardelli

Publications

Scar, a member of the WASp protein family, was discovered in Dictyostelium discoideum during a genetic screen for second-site mutations that suppressed a developmental defect. Disruption of the scar gene reduced the levels of cellular F-actin by 50%. To investigate the role of Scar in endocytosis, phagocytosis and endocytic membrane trafficking, processes that depend on actin polymerization, we have analyzed a Dictyostelium cell line that is genetically null for Scar. Rates of fluid phase macropinocytosis and phagocytosis are significantly reduced in the scar- cell-line. In addition, exocytosis of fluid phase is delayed in these cells and movement of fluid phase …


Inactivation Of Lmpa, Encoding A Limpii-Related Endosomal Protein, Suppresses The Internalization And Endosomal Trafficking Defects In Profilin-Null Mutants, Lesly A. Temesvari, Linyi Zhang, Brent Fodera, Klaus-Peter Janssen, Michael Schleicher, James A. Caradelli Jun 2000

Inactivation Of Lmpa, Encoding A Limpii-Related Endosomal Protein, Suppresses The Internalization And Endosomal Trafficking Defects In Profilin-Null Mutants, Lesly A. Temesvari, Linyi Zhang, Brent Fodera, Klaus-Peter Janssen, Michael Schleicher, James A. Caradelli

Publications

Profilin is a key phosphoinositide and actin-binding protein connecting and coordinating changes in signal transduction pathways with alterations in the actin cytoskeleton. Using biochemical assays and microscopic approaches, we demonstrate that profilin-null cells are defective in macropinocytosis, fluid phase efflux, and secretion of lysosomal enzymes but are unexpectedly more efficient in phagocytosis than wild-type cells. Disruption of the lmpA gene encoding a protein (DdLIMP) belonging to the CD36/LIMPII family suppressed, to different degrees, most of the profilin-minus defects, including the increase in F-actin, but did not rescue the secretion defect. Immunofluorescence microscopy indicated that DdLIMP, which is also capable of …


A Role For A Rab4-Like Gtpase In Endocytosis And In Regulation Of Contractile Vacuole Structure And Function In Dictyostelium Discoideum, John Bush, Lesly A. Temesvari, Juan Rodriguez-Paris, Greg Buczynski, James Cardelli Oct 1996

A Role For A Rab4-Like Gtpase In Endocytosis And In Regulation Of Contractile Vacuole Structure And Function In Dictyostelium Discoideum, John Bush, Lesly A. Temesvari, Juan Rodriguez-Paris, Greg Buczynski, James Cardelli

Publications

The small Mr Rab4-like GTPase, RabD, localizes to the endosomal pathway and the contractile vacuole membrane system in Dictyostelium discoideum. Stably transformed cell lines overexpressing a dominant negative functioning RabD internalized fluid phase marker at 50% of the rate of wild-type cells. Mutant cells were also slower at recycling internalized fluid. Microscopic and biochemical approaches indicated that the transport of fluid to large postlysosome vacuoles was delayed in mutant cells, resulting in an accumulation in acidic smaller vesicles, probably lysosomes. Also, RabD N121I-expressing cell lines missorted a small but significant percentage of newly synthesized lysosomal alpha-mannosidase precursor polypeptides. However, the …


Involvement Of The Vacuolar Proton-Translocating Atpase In Multiple Steps Of The Endo-Lysosomal System And In The Contractile Vacuole System Of Dictyostelium Discoideum, Lesly A. Temesvari, Juan M. Rodriguez-Paris, John M. Bush, Linyi Zhang, James A. Cardelli Jun 1996

Involvement Of The Vacuolar Proton-Translocating Atpase In Multiple Steps Of The Endo-Lysosomal System And In The Contractile Vacuole System Of Dictyostelium Discoideum, Lesly A. Temesvari, Juan M. Rodriguez-Paris, John M. Bush, Linyi Zhang, James A. Cardelli

Publications

We have investigated the effects of Concanamycin A (CMA), a specific inhibitor of vacuolar type H(+)-ATPases, on acidification and function of the endo-lysosomal and contractile vacuole (CV) systems of D. discoideum. This drug inhibited acidification and increased the pH of endo-lysosomal vesicles both in vivo and in vitro in a dose dependent manner. Treatment also inhibited endocytosis and exocytosis of fluid phase, and phagocytosis of latex beads. This report also confirms our previous conclusions (Cardelli et al. (1989) J. Biol. Chem. 264, 3454–3463) that maintenance of acidic pH in lumenal compartments is required for efficient processing and targeting of a …


Examination Of The Endosomal And Lysosomal Pathways In Dictyostelium Discoideum Myosin I Mutants, Lesly A. Temesvari, John M. Bush, Michelle D. Peterson, Kristine D. Novak, Margaret A. Titus, James A. Cardelli Mar 1996

Examination Of The Endosomal And Lysosomal Pathways In Dictyostelium Discoideum Myosin I Mutants, Lesly A. Temesvari, John M. Bush, Michelle D. Peterson, Kristine D. Novak, Margaret A. Titus, James A. Cardelli

Publications

The role of myosin Is in endosomal trafficking and the lysosomal system was investigated in a Dictyostelium discoideum myosin I double mutant myoB-/C-, that has been previously shown to exhibit defects in fluid-phase endocytosis during growth in suspension culture (Novak et al., 1995). Various properties of the endosomal pathway in the myoB-/C- double mutant as well as in the myoB- and myoC- single mutants, including intravesicular pH, and intracellular retention time and exocytosis of a fluid phase marker, were found to be indistinguishable from wild-type parental cells. The intimate connection between the contractile vacuole complex and the endocytic pathway in …


Characterization Of Lysosomal Membrane Proteins Of Dictyostelium Discoideum, Lesly A. Temesvari, Juan Rodriguez-Paris, John Bush, Theodore L. Steck, James Caradelli Oct 1994

Characterization Of Lysosomal Membrane Proteins Of Dictyostelium Discoideum, Lesly A. Temesvari, Juan Rodriguez-Paris, John Bush, Theodore L. Steck, James Caradelli

Publications

Highly purified lysosomes, prepared by magnetic fractionation of homogenates from Dictyostelium discoideum cells fed colloidal iron, were lysed under hypoosmotic conditions, and the membrane-associated proteins were subjected to gel electrophoresis. Thirteen major membrane polypeptides, ranging in molecular weight from 25,000 to 100,000 were identified. The isoelectric points of these proteins ranged from below 3.8 to greater than 7.0. Most of these proteins were stripped from membranes exposed to a chaotropic agent, 3,5-diodo-2-hydroxybenzoic acid lithium salt, and were therefore classified as peripheral membrane proteins. Twenty five glycoprotein species were detected by lectin blot analysis; 19 were classified as integral membrane proteins, …


A Rab4-Like Gtpase In Dictyostelium Discoideum Colocalizes With V-H(+)-Atpases In Reticular Membranes Of The Contractile Vacuole Complex And In Lysosomes, John Bush, Kathleen Nolta, Juan Rodriguez-Paris, Nancy Kaufmann, Theresa O'Halloran, Tracy Ruscetti, Lesly A. Temesvari, Theodore Steck, James Cardelli Oct 1994

A Rab4-Like Gtpase In Dictyostelium Discoideum Colocalizes With V-H(+)-Atpases In Reticular Membranes Of The Contractile Vacuole Complex And In Lysosomes, John Bush, Kathleen Nolta, Juan Rodriguez-Paris, Nancy Kaufmann, Theresa O'Halloran, Tracy Ruscetti, Lesly A. Temesvari, Theodore Steck, James Cardelli

Publications

In the course of screening a cDNA library for ras-related Dictyostelium discoideum genes, we cloned a 0.7 kb cDNA (rabD) encoding a putative protein that was 70% identical at the amino acid level to human Rab4. Rab4 is a small M(r) GTPase, which belongs to the Ras superfamily and functions to regulate endocytosis in mammalian cells. Southern blot analysis indicated that the rabD cDNA was encoded by a single copy gene while Northern blot analysis revealed that the rabD gene was expressed at relatively constant levels during growth and differentiation. Affinity-purified antibodies were prepared against a RabD fusion protein expressed …