Everything about Protein S totally explained
| Name = Protein S (alpha)
| HGNCid = 9456
| Symbol = PROS1
| AltSymbols =; PSA; PROS; PS 26; PS21; PS22; PS23; PS24; PS25; Protein S; protein Sa
| OMIM = 176880
| ECnumber =
| Homologene = 264
| MGIid = 1095733
| GeneAtlas_image1 = PBB_GE_PROS1_207808_s_at_tn.png
| Function =
| Component =
| Process =
| Orthologs =
}}
Protein S is a
vitamin K-dependent plasma
glycoprotein synthesized in the liver. In the circulation, Protein S exists in two forms: a free form and a complex form bound to
complement protein C4b.
Function
The best characterized function of Protein S is its role in the anti
coagulation pathway, it functions as a cofactor to
Protein C in the inactivation of
Factors Va and
VIIIa. Only the free form has cofactor activity.
Protein S can bind to negatively charged
phospholipids via the carboxylated GLA domain. This property allows Protein S to function in the removal of cells which are undergoing
apoptosis.
Apoptosis is a form of cell death that's used by the body to remove unwanted or damaged cells from tissues. Cells which are apoptotic (ie. in the process of
apoptosis) no longer actively manage the distribution of phospholipids in their outer membrane and hence begin to display negatively charged phospholipids, such as phosphatidyl serine, on the cell surface. In healthy cells, an ATP (
Adenosine triphosphate)-dependent enzyme removes these from the outer leaflet of the cell membrane. These negatively charged phospholipids are recognized by
phagocytes such as
macrophages. Protein S can bind to the negatively charged phospholipids and function as a bridging molecule between the apoptotic cell and the phagocyte. The bridging property of Protein S enhances the phagocytosis of the apoptotic cell, allowing it to be removed 'cleanly' without any symptoms of tissue damage such as
inflammation occurring.
Pathology
Protein S deficiency is a rare blood disorder which can lead to an increased risk of
thrombosis.
Further Information
Get more info on 'Protein S'.
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