Selectins Cd62elp

Masayuki Miyasaka, Department of Bioregulation, Osaka University Medical School, Osaka, Japan

Selectins are a family of three Ca2+-dependent transmembrane lectins i.e. L-selectin (CD62L), E-selectin (CD62E), P-selectin (CD62P) that initiate the tethering of leukocytes to activated endothelium under shear forces. They have a characteristic structural motif consisting of an N-terminal lectin domain, a domain with homology to epidermal growth factor (EGF), and a variable number of complement regulatory protein repeat sequences (Figure 1). L-Selectin is constitutively expressed on the majority of leukocytes, while E-selectin is often expressed by activated endothelium. P-Selectin is normally stored in a granules in platelets and the Weibel-Palade body in endothelial cells, and transported to the cell surface upon activation where it is expressed transiently. All selectins bind specific sialylated, fucosylated carbohydrates such as sialyl Lewis" (sLe"; Neu5Aca2-3Galpi-4(Fuca1-3)GlcNAc). Presentation of these carbohydrates in a clustered form on the protein backbone appears to confer high affinity to the sel-

P-Selectin (CD62P)

L-Selectlri (CD62L)

Figure 1 The selectins. The selectin family members have a unique domain structure consisting of the c-type lectin domain (LEC), epidermal growth factor-like domain (EGF) and complement regulatory protein domain with multiple short consensus repeats (SCR).

Figure 1 The selectins. The selectin family members have a unique domain structure consisting of the c-type lectin domain (LEC), epidermal growth factor-like domain (EGF) and complement regulatory protein domain with multiple short consensus repeats (SCR).

ectin ligands. As shown in Figure 2, the glycoprotein ligands for L-selectin, GlyCAM-1 and CD34 are expressed on high endothelial venules (HEVs) in peripheral lymph nodes. Another L-selectin ligand, MAdCAM-1, is expressed specifically on HEVs in Peyer's patches and mesenteric lymph nodes. Both E-selectin glycoprotein ligand, ESL-1, and P-selectin glycoprotein ligand, PSGL-1, are expressed in neutrophils.

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