Macrophages receptor, endocytosis

The cellular barriers include macrophages, eosinophils, phagocytes and natural killer (NK) cells. Some of these cells internalize macromolecules that they encounter in circulation or in tissues. This internalization takes place either by pinocytosis, receptor-mediated endocytosis or phagocytosis. The pinocytosis involves nonspecific membrane invagination. In contrast, receptor-mediated endocytosis involves specific macromolecules that are internalized after they bind to respective cell surface receptors. Endocytosis is not cell-specific and is carried out probably by all cells. 

They encapsulated poly(MA-CDA) into mannan-coated liposomes and evaluated superoxide production from mouse macrophages. The activity was three- to five-fold high compared with uncapsulated poly(MA-CDA) itself [5,11], suggesting that an increased incorporation of the polymer by the receptor-mediated endocytosis mediated the higher biological activity.. 

W. W. Liang, X. Shi, D. Deshpande, C. J. Malanga, and Y. Rojanasakul, Oligonucleotide targeting to alveolar macrophages by mannose receptor-mediated endocytosis, Biochim. Biophys. Acta, 1279 (1996) 227-234. 

The protein that transports iron around the body in blood and lymph, and indeed within the cell, is transferrin (500 kDa). It has two binding sites for iron (Fe " ) when no iron is bound, it is known as apotransferrin. Transferrin picks up not only the iron absorbed from the intestine but also that released from the macrophages and then transports it to the cells that require it, which is primarily the cells in the bone marrow but also other cells that are proliferating. For uptake into the cells, the transferrin binds to a receptor on the plasma membrane and then the complex enters the cell by endocytosis. The iron is released from the complex in the cytosol where it is bound by the intra-... 

Cellular components in atherosclerotic plaques include foam cells, which are transformed macrophages, and smooth muscle cells filled with cholesteryl esters. These cellular alterations result from endocytosis of modified lipoproteins via at least four species of scavenger receptors. Chemical modification of lipoproteins by free radicals creates ligands for... 

As mentioned in Chapter 21, there are several related receptors with similar structures. Two of them have a specificity for apolipoprotein E and can accept remnants of VLDL particles and chylomicrons.216 220 The LDL receptor-related protein is a longer-chain receptor.216 221 LDL particles, especially when present in excess or when they contain oxidized lipoproteins, may be taken up by endocytosis into macrophages with the aid of the quite different scavenger receptors.221 225 The uptake of oxidized lipoproteins by these receptors may be a major factor in promoting development of atherosclerosis (Box 22-B). On the other hand, scavenger receptor SR-B1, which is also present in liver cells, was recently identified as the receptor for HDL and essential to the "reverse cholesterol transport" that removes excess cholesterol for excretion in the bile.213/213a... 

Fujiwara, M., J.D. Baldeschwieler, and R.H. Grubbs. 1996. Receptor-mediated endocytosis of poly(acrylic acid)-conjugated liposomes by macrophages. Biochim Biophys Acta 1278 59. 

Matsumoto, K. et al., Insulin enhances macrophage scavenger receptor-mediated endocytotic uptake of advanced glycation endproducts, J. Biol. Chem. 273,8630-8637,1998). There is some interest in receptor-mediated endocytosis for drug delivery (Selbo, P.K., Hogset, A., Prasmickaite, L., and Berg, K Photochemical internalization a novel dmg delivery system. Tumour Biol. 23, 102-112, 2002). 

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