Endocytic uptake

The receptor-mediated form of endocytic uptake has been identified for a wide variety of physiological ligands, such as metabolites, hormones, immunoglobulins, and pathogens (e.g., virus and bacterial and plant toxins). Several endosomotropic receptors identified in cells are listed in Table 2. 

However, the initial step of uptake is a branch of the endocytic uptake and corresponds to one of the mechanisms described in the section on Initial Mode of Internalization. In most studies, clathrin-mediated or caveolae-mediated mechanisms are discussed. 

Dijkstra J, van Galen WJ, Scherphof GL. Effects of ammonium chloride and chloroquine on endocytic uptake of liposomes by Kupffer cells in vitro. Biochim Biophys Acta 1983 804(l) 58-67. 

However, in general, endocytic uptake is a minor process for the enterocytes. In contrast, endocytic uptake of macromolecules and microparticles is carried out extensively by the M cells of the... 

As described above (Section 6.2.2), the Peyer s patches belong to the gut-associated lymphoid tissue (GALT) and participate in the process of antigen sampling and presentation to the immune system. Specialized antigen-presenting epithelial cells cover the patches, called M-cells (modified epithelial cells). Unlike the intestinal enterocytes, the M cells of the Peyer s patches are capable of extensive endocytic uptake of macromolecules and microparticles (Figure 6.15). 

Metabolic cell-surface engineering to promote the endocytic uptake of ligands... 

Seetharam B. Receptor-mediated endocytosis of cobalamin (vitamin B12). Annu. Rev. Nutr. 1999 19 173-195. Boonyarattanakalin S, Martin SE, Sun Q, Peterson BR. A Synthetic Mimic of Human Fc Receptors Defined Chemical Modification of Cell Surfaces Enables Efficient Endocytic Uptake of Human Immunoglobulin-G. J. Am. Chem. Soc. 2006 128 11463-11470. 

The next step in the entry process is endocytic uptake of the bound toxin. The uptake is comparatively slow and appears to occur from clathrin-coated pits (Morris ef al., 1985). Once in endosomes, the toxin is exposed to acidic conditions a pH below 5.3 is necessary for the penetration to the cytosol (Sandvig and Olsnes, 1981). If acidification of the endosomes is prevented by exposure of the cells to NH4CI or monensin, the cells are protected from poisoning. However, the protection can be overcome if the cells are exposed to buffer with acidic pH (Sandvig and Olsnes, 1981). Under these conditions toxin bound at the cell surface penetrates directly through the surface membrane (Moskaug etal., 1988). 

There are, however, many unsolved problems concerning toxicity, endocytic uptake and immunogenicity of DIVEMA. In order to learn more about the structure dependency of these properties, we sythesized some DIVEMA derivatives and investigated DIVEMA and the new derivatives with appropriate routine biological test systems. 

Christensen El, Gliemann J, Moestrup SK. Renal tubule gp330 is a calcium binding receptor for endocytic uptake of protein. J Histochem Cytochem 1992 40 1481-1490. 

We have found that clathrin-coated pits and vesicles are the morphological structures responsible for endocytic uptake of PrP (Shyng et al.,... 

Potocky T B, Menon A K, Gellman S H (2003). Cytoplasmic and nuclear delivery of TAT-derived peptide and a beta-peptide after endocytic uptake into HeLa cells. J. Biolog. Chem. 278 50188-50194. 

Nonviral carriers have been examined in attempts to protect and try to achieve intracellular delivery of oligonucleotides such as plasmid DNA and siRNA [109]. Polyacetals would be expected to undergo enhanced rates of degradation upon endocytic uptake. In addition to the aforementioned acetal/ketal polyamidoamines 23 (Figure 13.5b),... 

Other work has been described to determine the potential for polyacetals to be used for endocytic uptake of com-plexed oligonucleotides. 

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