P selectin (SELP) is a 140kDa protein that is stored in the alpha-granules of platelets and Weibel-Palade bodies of endothelial cells. SELP mediates rapid rolling of leukocyte rolling over vascular surfaces during the initial steps in inflammation through interaction with PSGL1. P selectin is a cell adhesion molecule on the surface of activated endothelial cells. Cellular adhesion molecules are a large family of proteins that attach the cytoskeleton and intracellular signaling cascades with the extracellular environment. SELP is a calcium-dependent receptor for myeloid cells that binds to sialylated forms of Lewis blood group carbohydrate antigens on neutrophils and monocytes. This protein redistributes to the plasma membrane during platelet activation and degranulation and mediates the interacton of activated endothelial cells or platelets with leukocytes.
This gene is a member of the semaphorin family and encodes a protein with an Ig-like C2-type (immunoglobulin-like) domain, a PSI domain and a Sema domain. This secreted protein can function as either a chemorepulsive agent, inhibiting axonal outgrowth, or as a chemoattractive agent, stimulating the growth of apical dendrites. In both cases, the protein is vital for normal neuronal pattern development. Increased expression of this protein is associated with an schizophrenia and is seen in a variety of human tumor cell lines. Also, aberrant release of this protein is associated with an the progression of Alzheimer's disease.
Semaphorin-4A, also known as Semaphorin-B, SEMA4A, Sema B and SEMAB, is a single-pass type I membrane protein which belongs to thesemaphorin family. It inhibits axonal extension by providing local signals to specify territories inaccessible for growing axons. Semaphorin-4A contains one Ig-like C2-type domain, one PSI domain and one Sema domain. Defects in SEMA4A are the cause of retinitis pigmentosa type 35 (RP35) which leads to degeneration of retinal photoreceptor cells. Patients typically have night vision blindness and loss of midperipheral visual field. As their condition progresses, they lose their far peripheral visual field and eventually central vision as well. Defects in SEMA4A are also the cause of cone-rod dystrophy type 10 (CORD10) which are inherited retinal dystrophies belonging to the group of pigmentary retinopathies. CORDs are characterized by retinal pigment deposits visible on fundus examination, predominantly in the macular region, and initial loss of cone photoreceptors followed by rod degeneration. Semaphorins are secreted, transmembrane, and GPI-linked proteins, defined by cysteine-rich semaphorin protein domains, that have important roles in a variety of tissues. Semaphorins have been implicated in diverse developmental processes such as axon guidance during nervous system development and regulation of cell migration.
Semaphorin-4B is a single-pass type I membrane protein. SEMA4B is a member of the semaphorin family. The class 4 semaphorins are integral membrane proteins that are widely expressed throughout the nervous system. SEMA4B is a single-pass type I membrane protein and contains one Ig-like C2-type (immunoglobulin-like) domain; one PSI domain and one Sema domain. Human SEMA4B is expressed in neurons. SEMA4B inhibits axonal extension by providing local signals to specify territories inaccessible for growing axons. SEMA4B negatively regulates basophil-mediated Th2 and humoral memory responses.
The class 4 semaphorins are integral membrane proteins that are widely expressed throughout the nervous system. SEMA4B is a single-pass type I membrane protein and contains one Ig-like C2-type (immunoglobulin-like) domain; one PSI domain and one Sema domain. Human SEMA4B is expressed in neurons. SEMA4B inhibits axonal extension by providing local signals to specify territories inaccessible for growing axons. SEMA4B negatively regulates basophil-mediated Th2 and humoral memory responses.
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