![]() Going from N-terminal to C-terminal, it is broken down into: C-type lectin domain (CTLD), Epidermal Growth Factor (EGF)-like domain, two sequence consensus repeat (SCR) domains, a cleavage site, transmembrane domain and a 17 amino acid cytoplasmic tail. (A) L-selectin is a type I transmembrane glycoprotein. L-selectin is organized into distinct structural domains: a ligand binding calcium-dependent (C-type) lectin domain (CTLD), an EGF-like domain, two complement-like repeat sequences and an extracellular cleavage site ( Figure 1A).įigure 1. It is highly likely that altered glycosylation patterns in L-selectin could dictate cell-specific functions, but this has not been explored in any detail. However, the actual molecular weight of L-selectin differs between cell types-ranging from 65 kDa in lymphocytes to 100 kDa in neutrophils and is due to cell type-specific glycosylation ( 4– 10). Splicing of the exons into mature mRNA is translated to form a protein product with a predicted molecular weight of 30 kDa. FOXO1 regulates transcription of the human sell gene ( 1, 2), whereas chromosome immunoprecipitation experiments identify other transcription factors (Mzf1, Klf2, Sp1, Ets1, and Irf1) in regulating the mouse sell gene ( 3). L-selectin consists of ten exons spanning a region of ~21.0 kb. The human L-selectin gene ( sell) is located on the long arm of chromosome 1 (1q24.2), and is arranged in tandem with its family members (in the order: L-, P-, and E-selectin). Finally, we will discuss how ectodomain shedding of L-selectin during monocyte TEM is essential for the establishment of front-back cell polarity, bestowing emigrated cells the capacity to chemotax toward sites of damage. A significant focus on the L-selectin cytoplasmic tail and its proposed contribution to signaling via the ezrin-radixin-moesin (ERM) family of proteins will be outlined. We will describe how each domain within L-selectin contributes to adhesion, migration and signal transduction. We will list some of the diverse glycans known to support L-selectin-dependent adhesion, within luminal and abluminal regions of the vessel wall. In this review we will detail the expression of L-selectin in different immune cell subsets, and its influence on cell behavior. Although the signals downstream of L-selectin-dependent adhesion are poorly understood, they will invariably involve the short 17 amino acid cytoplasmic tail. The N-terminal calcium-dependent (C-type) lectin domain of L-selectin interacts with numerous glycans, including sialyl Lewis X (sLe x) for tethering/rolling and proteoglycans for TEM. There is now mounting evidence in the literature to suggest that L-selectin plays a role in regulating monocyte protrusion during transendothelial migration (TEM). Since its identification in 1983, L-selectin has been extensively characterized as a tethering/rolling receptor. L-selectin (CD62L) is a type-I transmembrane glycoprotein and cell adhesion molecule that is expressed on most circulating leukocytes. King's College London, School of Cardiovascular Medicine and Sciences, BHF Center of Research Excellence, London, United Kingdom.Aleksandar Ivetic * Hannah Louise Hoskins Green Samuel James Hart
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