Basigin (BSG) also known as extracellular matrix metalloproteinase inducer (EMMPRIN) or cluster of differentiation 147 (CD147) is a protein that in humans is encoded by the BSG gene. [5] [6] [7] This protein is a determinant for the Ok blood group system. There are three known antigens in the Ok system; the most common being Oka (also called OK1), OK2 and OK3. Basigin has been shown to be an essential receptor on red blood cells for the human malaria parasite, Plasmodium falciparum. [8] The common isoform of basigin (basigin-2) has two immunoglobulin domains, and the extended form basigin-1 has three. [9]
Basigin is a member of the immunoglobulin superfamily, with a structure related to the putative primordial form of the family. As members of the immunoglobulin superfamily play fundamental roles in intercellular recognition involved in various immunologic phenomena, differentiation, and development, basigin is thought also to play a role in intercellular recognition (Miyauchi et al., 1991; Kanekura et al., 1991). [10] [11]
It has a variety of functions. In addition to its metalloproteinase-inducing ability, basigin also regulates several distinct functions, such as spermatogenesis, expression of the monocarboxylate transporter and the responsiveness of lymphocytes. [6] Basigin is a type I integral membrane receptor that has many ligands, including the cyclophilin (CyP) proteins Cyp-A and CyP-B and certain integrins. [12] [13] [14] Basigin also serves as a receptor for S100A9 and platelet glycoprotein VI, and basigin-1 acts as a receptor for the rod-derived cone viability factor. [9] It is expressed by many cell types, including epithelial cells, endothelial cells, neural progenitor cells [15] and leukocytes. The human basigin protein contains 269 amino acids that form two heavily glycosylated C2 type immunoglobulin-like domains at the N-terminal extracellular portion. A second form of basigin has also been characterized that contains one additional immunoglobulin-like domain in its extracellular portion. [6]
Basigin has been shown to interact with Ubiquitin C. [16]
Basigin has been shown to form a complex with monocarboxylate transporters in the retina of mice. Basigin appears to be required for proper placement of MCTs in the membrane. In the Basigin null mouse, the failure of MCTs to integrate with the membrane may be directly linked to a failure of nutrient transfer in the retinal pigmented epithelium (the lactates transported by MCTs 1, 3, and 4 are essential nutrients for the developing RPE), resulting in loss of sight in the null animal. [17]
Basigin interacts with the fourth C-type lectin [ circular reference ] domain in the receptor Endo180 [18] to form a molecular epithelial-mesenchymal transition [ citation needed ] suppressor complex that if disrupted results in the induction of invasive prostate epithelial cell behavior associated with poor prostate cancer survival. [19]
It have been shown that Atorvastatin suppresses CD147 and MMP-3 expression. [20] [21]
It has recently (November 2011) been found that basigin is a receptor that is essential to erythrocyte invasion by most strains of Plasmodium falciparum , the most virulent species of the plasmodium parasites that cause human malaria. It is hoped that by developing antibodies to the parasite ligand for Basigin, Rh5, a better vaccine for malaria might be found. [8] Basigin is bound by the PfRh5 protein on the surface of the malaria parasite.[ citation needed ]
Meplazumab, an anti-CD147 antibody, was tested in patients with SARS-CoV-2 pneumonia. [22]
Some of these claims have been challenged by another group of scientists who found no evidence of a direct role for basigin in either binding the viral spike protein or promoting lung cell infection. [23]
More recent studies suggests CD147 as SARS-CoV-2 entry receptor of platelets and megakaryocytes, leading to hyperactivation and thrombosis, that differs from common cold coronavirus CoV-OC43. Incubation of megakaryocyte cells with SARS-CoV-2 resulted in a significant increase in the proinflammatory transcripts LGALS3BP and S100A9. Notably, CD147 antibody-mediated blocking significantly reduced the expression of S100A9, and S100A8 on megakaryocytes following incubation with SARS-CoV-2. These data indicate that megakaryocytes and platelets actively take up SARS-CoV-2 virions, likely via an ACE-2-independent mechanism. [24]
Another study states that platelets challenged with SARS-CoV-2 undergo activation, dependent on the CD147 receptor. [25] Yet SARS-CoV-2 does not replicate in human platelets.
Yet another study describes high-interaction coupling of N-RBD of SARS-CoV-2 and CD147 as the main way of infecting lymphocytes allegedly leading to Acquired Immune Deficiency Syndrome. [26]
Platelets or thrombocytes are a component of blood whose function is to react to bleeding from blood vessel injury by clumping, thereby initiating a blood clot. Platelets have no cell nucleus; they are fragments of cytoplasm derived from the megakaryocytes of the bone marrow or lung, which then enter the circulation. Platelets are found only in mammals, whereas in other vertebrates, thrombocytes circulate as intact mononuclear cells.
CD32, also known as FcγRII or FCGR2, is a surface receptor glycoprotein belonging to the Ig gene superfamily. CD32 can be found on the surface of a variety of immune cells. CD32 has a low-affinity for the Fc region of IgG antibodies in monomeric form, but high affinity for IgG immune complexes. CD32 has two major functions: cellular response regulation, and the uptake of immune complexes. Cellular responses regulated by CD32 include phagocytosis, cytokine stimulation, and endocytic transport. Dysregulated CD32 is associated with different forms of autoimmunity, including systemic lupus erythematosus. In humans, there are three major CD32 subtypes: CD32A, CD32B, and CD32C. While CD32A and CD32C are involved in activating cellular responses, CD32B is inhibitory.
A megakaryocyte is a large bone marrow cell with a lobated nucleus that produces blood platelets (thrombocytes), which are necessary for normal clotting. In humans, megakaryocytes usually account for 1 out of 10,000 bone marrow cells, but can increase in number nearly 10-fold during the course of certain diseases. Owing to variations in combining forms and spelling, synonyms include megalokaryocyte and megacaryocyte.
Thrombopoietin (THPO) also known as megakaryocyte growth and development factor (MGDF) is a protein that in humans is encoded by the THPO gene.
Cluster of differentiation 40, CD40 is a type I transmembrane protein found on antigen-presenting cells and is required for their activation. The binding of CD154 (CD40L) on TH cells to CD40 activates antigen presenting cells and induces a variety of downstream effects.
Platelet endothelial cell adhesion molecule (PECAM-1) also known as cluster of differentiation 31 (CD31) is a protein that in humans is encoded by the PECAM1 gene found on chromosome17q23.3. PECAM-1 plays a key role in removing aged neutrophils from the body.
The immunoglobulin superfamily (IgSF) is a large protein superfamily of cell surface and soluble proteins that are involved in the recognition, binding, or adhesion processes of cells. Molecules are categorized as members of this superfamily based on shared structural features with immunoglobulins ; they all possess a domain known as an immunoglobulin domain or fold. Members of the IgSF include cell surface antigen receptors, co-receptors and co-stimulatory molecules of the immune system, molecules involved in antigen presentation to lymphocytes, cell adhesion molecules, certain cytokine receptors and intracellular muscle proteins. They are commonly associated with roles in the immune system. Otherwise, the sperm-specific protein IZUMO1, a member of the immunoglobulin superfamily, has also been identified as the only sperm membrane protein essential for sperm-egg fusion.
Platelet factor 4 (PF4) is a small cytokine belonging to the CXC chemokine family that is also known as chemokine ligand 4 (CXCL4). This chemokine is released from alpha-granules of activated platelets during platelet aggregation, and promotes blood coagulation by moderating the effects of heparin-like molecules. Due to these roles, it is predicted to play a role in wound repair and inflammation. It is usually found in a complex with proteoglycan.
Platelet glycoprotein VI (GPVI) is a glycoprotein receptor for collagen which is expressed in platelets. In humans, glycoprotein VI is encoded by the GP6 gene. It was first cloned in 2000 by several groups including that of Martine Jandrot-Perrus from INSERM.
Integrin alpha-2, or CD49b, is a protein which in humans is encoded by the CD49b gene.
CD63 antigen is a protein that, in humans, is encoded by the CD63 gene. CD63 is mainly associated with membranes of intracellular vesicles, although cell surface expression may be induced.
Peptidyl-prolyl cis-trans isomerase B is an enzyme that is encoded by the PPIB gene. As a member of the peptidyl-prolyl cis-trans isomerase (PPIase) family, this protein catalyzes the cis-trans isomerization of proline imidic peptide bonds, which allows it to regulate protein folding of type I collagen. Generally, PPIases are found in all eubacteria and eukaryotes, as well as in a few archaebacteria, and thus are highly conserved.
Platelet membrane glycoproteins are surface glycoproteins found on platelets (thrombocytes) which play a key role in hemostasis. When the blood vessel wall is damaged, platelet membrane glycoproteins interact with the extracellular matrix.
CD81 molecule, also known as CD81, is a protein which in humans is encoded by the CD81 gene. It is also known as 26 kDa cell surface protein, TAPA-1, and Tetraspanin-28 (Tspan-28).
Junctional adhesion molecule A is a protein that in humans is encoded by the F11R gene. It has also been designated as CD321.
Transmembrane activator and CAML interactor (TACI), also known as tumor necrosis factor receptor superfamily member 13B (TNFRSF13B) is a protein that in humans is encoded by the TNFRSF13B gene.
Leukocyte-associated immunoglobulin-like receptor 1 is a protein that in humans is encoded by the LAIR1 gene. LAIR1 has also been designated as CD305.
Tumor necrosis factor receptor superfamily member 12A also known as the TWEAK receptor (TWEAKR) is a protein that in humans is encoded by the TNFRSF12A gene.
Polyadenylate-binding protein 4 (PABPC4) is a protein that in humans is encoded by the PABPC4 gene.
Calcium modulating ligand, also known as calcium-modulating cyclophilin ligand, is a signalling protein recognized by the TNF receptor TACI.