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Category: Microbial Genetics and Molecular Biology
Lectin Receptors Expressed on Myeloid Cells, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555819194/9781555819187_Chap25-1.gif /docserver/preview/fulltext/10.1128/9781555819194/9781555819187_Chap25-2.gifAbstract:
Lectins, defined as proteins that recognize carbohydrates, perform numerous essential biological functions. Recognizing a diverse array of carbohydrate structures, vertebrate lectins have been subdivided into several structurally distinct families which can be located intracellularly (such as the intracellular M-type family of lectins, which function primarily in the glycoprotein secretory pathway), in the plasma membrane (such as some members of the C-type lectin and Siglec [sialic acid-binding immunoglobulin-type lectin] families, which are involved in pathogen recognition and immune regulation), or are secreted into the extracellular milieu (such as some members of the galectin family, which serve several homeostatic and immune functions) ( Table 1 ). We will restrict our discussion here to selected myeloid- and plasma membrane-expressed members of only two families, the C-type lectins and Siglecs. We will provide a brief overview of each family and then focus on selected illustrative and detailed examples that highlight how these lectins influence myeloid cell functioning in health and disease. For an overview on the other lectin families, the reader is referred to an excellent website (http://www.imperial.ac.uk/research/animallectins/ctld/lectins.html).
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Siglecs in humans and mice. There are two subgroups of Siglecs: One group contains Siglecs that are conserved in all mammalian species and the other group contains CD33-related Siglecs that appear to be undergoing rapid evolution in primates. The cell types expressing highest levels of each Siglec are indicated. B, B cell; Eos, eosinophil; Mac, macrophage; mDC, myeloid dendritic cell; Mon, monocyte; Neu, neutrophil; NK, NK cell; Oli, oligodendrocyte; Ost, osteoclast; pDC, plasmacytoid dendritic cell; Pla, placental syncytiotrophoblast; Sch, Schwann cell.
Siglecs in humans and mice. There are two subgroups of Siglecs: One group contains Siglecs that are conserved in all mammalian species and the other group contains CD33-related Siglecs that appear to be undergoing rapid evolution in primates. The cell types expressing highest levels of each Siglec are indicated. B, B cell; Eos, eosinophil; Mac, macrophage; mDC, myeloid dendritic cell; Mon, monocyte; Neu, neutrophil; NK, NK cell; Oli, oligodendrocyte; Ost, osteoclast; pDC, plasmacytoid dendritic cell; Pla, placental syncytiotrophoblast; Sch, Schwann cell.
Selected signal transduction cascades induced by C-type lectin receptors. Activation receptors, such as Dectin-1, Dectin-2, Mincle, and MCL, induce cellular responses primarily through Syk kinase, although other pathways can be involved, such as those induced by Raf-1. Inhibitory receptors, such as MICL, activate protein tyrosine phosphatases (PTPs, such as SHP-1), which attenuate activation pathways. DNGR-1 (CLEC9A), not discussed in the text, is an actin-binding receptor expressed by CD8+ DCs and involved in antigen cross-presentation. Reprinted from reference 329 , with permission.
Selected signal transduction cascades induced by C-type lectin receptors. Activation receptors, such as Dectin-1, Dectin-2, Mincle, and MCL, induce cellular responses primarily through Syk kinase, although other pathways can be involved, such as those induced by Raf-1. Inhibitory receptors, such as MICL, activate protein tyrosine phosphatases (PTPs, such as SHP-1), which attenuate activation pathways. DNGR-1 (CLEC9A), not discussed in the text, is an actin-binding receptor expressed by CD8+ DCs and involved in antigen cross-presentation. Reprinted from reference 329 , with permission.
Dectin-1 can mediate the nonopsonic phagocytosis of fluorescently labeled fungal particles (green) via actin (red)-based phagocytic cups. Reprinted from reference 155 , with permission.
Dectin-1 can mediate the nonopsonic phagocytosis of fluorescently labeled fungal particles (green) via actin (red)-based phagocytic cups. Reprinted from reference 155 , with permission.
The macrophage mannose receptor. Structure of the MR indicating its exogenous and endogenous ligands (including those in tissues). Mɸ, macrophage; LDL, low-density lipoprotein; HBV, hepatitis B virus; CPS, capsular polysaccharide; SEA, secreted egg antigen; Adam-13, a disintegrin and metalloprotease 13. Reprinted from reference 300 , with permission.
The macrophage mannose receptor. Structure of the MR indicating its exogenous and endogenous ligands (including those in tissues). Mɸ, macrophage; LDL, low-density lipoprotein; HBV, hepatitis B virus; CPS, capsular polysaccharide; SEA, secreted egg antigen; Adam-13, a disintegrin and metalloprotease 13. Reprinted from reference 300 , with permission.