Search results for "ENDOCYTOSIS"
showing 10 items of 185 documents
Orthogonal Click Conjugation to the Liposomal Surface Reveals the Stability of the Lipid Anchorage as Crucial for Targeting
2016
Synthetic access to multiple surface decorations are a bottleneck in the development of liposomes for receptor mediated targeting. This opens a complex multiparameter space, exploration of which is severely limited in terms of sample numbers and turnaround times. Here, we unlock this technological barrier by a combination of a milligram-scale liposome formulation using dual centrifugation and orthogonal click chemistry on the liposomal surface. Application of these techniques to conceptually new amphiphilic compounds, which feature norbornene and alkyne groups at the apex of sterically stabilizing, hyperbranched polyglycerol moieties, revealed a particular influence of the membrane anchor o…
Analyzing Protein-Protein Spatial-Temporal Dependencies from Image Sequences Using Fuzzy Temporal Random Sets
2008
Total Internal Reflection Fluorescence Microscopy (TIRFM) allows us to image fluorescenttagged proteins near the plasma membrane of living cells with high spatial-temporal resolution. Using TIRFM imaging of GFP-tagged clathrin endocytic proteins, areas of fluorescence are observed as overlapping spots of different sizes and durations. Standard procedures to measure protein-protein colocalization of dual labeled samples threshold the original graylevel images to segment areas covered by different proteins. This binary logic is not appropriate as it leaves a free tuning parameter which can influence the conclusions. Moreover, these procedures rely on simple statistical analysis based on corre…
Microcells Development and Endocytosis Ability Morphological and Quantitative Characterization in HeLa Cancer Cells
2008
Determination of endocytotic ability of cancer cells could improve tumor treatment results. The aim of this study was to investigate morphological aspects of development in HeLa (Henrietta Lacks cervical cancer cells) microcells and to quantitatively estimate the endocytotic capability of these cells.
Uptake of endocytic markers by rice cells: variations related to the growth phase.
2001
Endocytosis is now considered a basic cellular process common to plant cells. Although both non-specific and receptor-mediated endocytosis appear to take place in plant cells, the physiological role of the latter remains unclear. We have investigated the endocytic process in rice cell suspensions using two biotinylated proteins, peroxidase and bovine serum albumin (bHRP and bBSA), as markers. First, we show that markers are internalized by rice cells and appear in intracellular membranes. The uptake of the two markers is temperature dependent, saturable with time and markers dose and it is competed by free biotin. Thus, it shows the properties of a receptor-mediated process. We also show th…
Isoproterenol inhibits fluid-phase endocytosis from early to late endosomes
1999
We have shown recently that isoproterenol affects both the cellular location and the morphology of late endosomes in a pH-dependent manner [Marjomäki et al., Eur. J. Cell Biol. 65, 1-13 (1994)]. In this study, using fluorescence and quantitative electron microscopy, we wanted to examine further what is the fate of internalized markers during their translocation from early to late endosomes under isoproterenol treatment. Fluorescein dextran internalized for 30 min (10-min pulse followed by a 20-min chase) showed accumulation in the cellular periphery during isoproterenol treatment in contrast to the control cells, which accumulated dextran in the perinuclear region. Quantitative electron mic…
At reduced temperature, endocytic membrane traffic is blocked in multivesicular carrier endosomes in rat cardiac myocytes.
1998
Temperatures around 20 degrees C are known to block degradation of endocytosed material by preventing its transport to lysosomes, accordingly reduced temperature has been widely used to define endosomes. Newer studies have revealed that the low temperature block is proximal to perinuclear late endosomes, but it is not clear whether the block is already in early endosomes, or whether the traffic proceeds to multivesicular carrier endosomes which mediate transport from early to late compartments. We have now focused on this problem using rat cardiac myocytes. First, cell fractionation on Percoll gradients showed that at reduced temperatures (22 degrees C and 26 degrees C), with prolonged chas…
Mobilization of late-endosomal cholesterol is inhibited by Rab guanine nucleotide dissociation inhibitor
2000
AbstractCholesterol entering cells in low-density lipoproteins (LDL) via receptor-mediated endocytosis is transported to organelles of the late endocytic pathway for degradation of the lipoprotein particles. The fate of the free cholesterol released remains poorly understood, however. Recent observations suggest that late-endosomal cholesterol sequestration is regulated by the dynamics of lysobisphosphatidic acid (LBPA)-rich membranes [1]. Genetic studies have pinpointed a protein, Niemann–Pick C-1 (NPC-1), that is required for the mobilization of late-endosomal/lysosomal cholesterol by an unknown mechanism [2]. Here, we report the removal of accumulated cholesterol by overexpression of the…
Candida albicans ABG1 gene is involved in endocytosis.
2009
The human fungal pathogen Candida albicans undergoes reversible morphogenetic transitions between yeast, hyphal and pseudohyphal forms. The fungal vacuole actively participates in differentiation processes and plays a key role supporting hyphal growth. The ABG1 gene of C. albicans encodes an essential protein located in the vacuolar membranes of both yeast and hyphae. Using fluorescence microscopy of a green fluorescent protein-tagged version of Abg1p, a fraction of the protein was detected in hyphal tips, not associated with vacuolar membranes. Live cell imaging of emerging germ tubes showed that Abg1p migrated to the polarized growth site and colocalized with endocytic vesicles. Phenotypi…
Dendritic cells and the handling of antigen
2003
Dendritic cells (DC) are a sparsely distributed, migratory group of bone marrow-derived leucocytes that are specialized for the uptake, transport, processing and presentation of antigens to T cells [1,2]. At an immature stage of development DC are considered as the first-line sentinels in immune surveillance of peripheral tissues, including epithelia of the skin and mucosal surfaces, where they sample continuously the antigenic local microenvironment by uptake of self- and exogenous antigen via macropinocytosis/endocytosis [3,4]. The efficiency of DC to initiate an immune response against infectious disease is due to their constant trafficking between peripheral tissues and draining lymph n…
Inhibition of Transfer to Secondary Receptors by Heparan Sulfate-Binding Drug or Antibody Induces Noninfectious Uptake of Human Papillomavirus
2007
ABSTRACT Infection with various human papillomaviruses (HPVs) induces cervical cancers. Cell surface heparan sulfates (HS) have been shown to serve as primary attachment receptors, and molecules with structural similarity to cell surface HS, like heparin, function as competitive inhibitors of HPV infection. Here we demonstrate that the N , N ′-bisheteryl derivative of dispirotripiperazine, DSTP27, efficiently blocks papillomavirus infection by binding to HS moieties, with 50% inhibitory doses of up to 0.4 μg/ml. In contrast to short-term inhibitory effects of heparin, pretreatment of cells with DSTP27 significantly reduced HPV infection for more than 30 h. Using DSTP27 and heparinase, we fu…