As an industry leader specializing in customized services, in addition to providing non-IgG antibody products and services, Creative Biolabs also provides IgA receptor-pIgR related introduction to support the specific needs of customers around the world.
Introduction of PIgR
The polymeric immunoglobulin receptor (pIgR) is a highly glycosylated transmembrane protein encoded by the PIGR gene. PIgR is a kind of Fc receptor, which is mainly distributed in the epithelium on the gastrointestinal mucosal surface. PIgR is closely related to the process of transcytosis. The composition of pIgR is very complex, which can be roughly divided into three parts: intracellular part, transmembrane part and extracellular part. There are six domains outside the cell: five conserved domains mainly participate in the Ig polymer binding process while the other domain plays an important role in the proteolysis of the complex. Intracellular domains are inseparable from the signals of intracellular sorting and endocytosis.
Fig.1 Structure of pIgR. (Wei, 2021)
PIgR Function
There are a large number of harmful microorganisms in the gastrointestinal tract, and the mucosal barrier is a major mechanism to prevent them from entering the host. The defense mechanism of the mucosal surface relies on polymeric immunoglobulin (pIg). PIgR can specifically bind to pIgs, however, it has no response to monomeric immunoglobulins. PIgR can help pIg, especially dimeric immunoglobulin A and polymeric immunoglobulin M, to transport across the epithelial barrier. After reaching the lumen side, a part of pIgR is hydrolyzed to release Ig and form secretory immunoglobulin (SIg). SIg can regulate microbial communities and pathogenic microorganisms through a variety of mechanisms to mediate host protection. Therefore, PIgRs play a vital role in mucosal infection and immune processes. In addition, SIg exerts an influence on host immunity and mucosal tolerance by regulating inflammatory cytokines and initiating immune cells.
Fig.2 The pathway of transcytosis. (Kaetzel, 2001)
Regulation of the PIgR/SIg System
PIgR expression and SIg secretion are affected by many factors including immunity, hormones and environment. Immune system mediators, including interferon γ and tumor necrosis factor α, are the main factors that regulate the expression of pIgR. Although most studies on pIgR are focused on mucosal defense, some studies have also shown changes in pIgR expression in cancer, which may provide new evidence for other functions of pIgR.
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References
- Wei, H.; Wang, J. Y. Role of Polymeric Immunoglobulin Receptor in IgA and IgM Transcytosis. International Journal of Molecular Sciences. 2021, 22(5): 2284.
- 2. Kaetzel, C. S. Polymeric Ig receptor: defender of the fort or Trojan horse. Current Biology. 2001, 11(1): R35-R38.
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