Basigin also known as extracellular matrix metalloproteinase inducer or cluster of differentiation 147 is a protein that in humans is encoded by the BSG gene. 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, OK2 and OK3. Basigin has been shown to be an essential receptor on red blood cells for the human malaria parasite, Plasmodium falciparum.
Function
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. 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. Basigin is a type I integral membrane receptor that has many ligands, including the cyclophilin proteins Cyp-A and CyP-B and certain integrins. It is expressed by many cell types, including epithelial cells, endothelial cells and leukocytes. The human basigin protein contains 269 amino acids that form two heavily glycosylatedC2 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.
Interactions
Basigin has been shown to interact with Ubiquitin C. 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, resulting in loss of sight in the null animal. Basigin interacts with the fourth C-type lectin domain in the receptor Endo180 to form a molecular epithelial-mesenchymal transition suppressor complex that if disrupted results in the induction of invasive prostate epithelial cell behavior associated with poor prostate cancer survival.
It has recently 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 parasiteligand for Basigin, Rh5, a better vaccine for malaria might be found. Basigin is bound by the PfRh5 protein on the surface of the malaria parasite.
The host-cell-expressed basigin may bind spike protein of SARS-CoV-2 and possibly be involved in host cell invasion. Consequently, meplazumab, a humanized anti-CD147 antibody, has been tested in patients with SARS-CoV-2 pneumonia. The exact role and significance of basigin in COVID-19 is still unknown.
