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The double-edged sword of immune response: How do peptide receptors mediate infection and immunosuppression?
The function of the immune system is to recognize and respond to foreign pathogens, in which formed peptide receptors (FPRs) play a key role. FPRs are a class of G protein-coupled receptors that specifically bind to N-formyl peptides, which are produced by degradation of bacteria or host cells. There are three different isoforms of human FPR, namely FPR1, FPR2 and FPR3. These receptors can not only trigger immune responses, but also inhibit the activity of the immune system in certain circumstances, making them a double-edged sword for both infection and immunosuppression.
The formation of peptide receptors as signal recognition elements plays a vital role in initiating inflammatory responses.
Discovery of peptide receptor formation
Studies in the 1970s showed that a series of oligopeptides containing N-formylmethionine could stimulate rabbit and human neutrophils, which was the result of promoting their directional migration through a receptor-dependent mechanism. These oligopeptides were mainly derived from bacteria or their synthetic analogs, indicating that N-formyl peptides are of great significance in chemotaxis. As more research was done, the role of FPRs was more clearly defined and they were named peptide receptors, named for their ability to bind and activate these oligopeptides.
Structure and Function
FPR belongs to a class of receptors with seven hydrophobic transmembrane regions. The stability of its structure depends on multiple interactions, including possible salt bridge formation and interactions between positively charged residues and negatively charged phosphate groups. In particular, the Arg163 residue may form an interaction with the ligand-binding site of FPR, enabling it to bind to a variety of N-formyl peptides and further trigger physiological responses in cells.
The complexity of FPR's structure and function enables it to participate in multiple functions of promoting and inhibiting immune responses.
Signaling pathways
Activation of FPR triggers many changes within the cell, including rearrangement of the cytoskeleton, which in turn promotes cell migration. This process is mainly carried out through G protein-dependent activation of phospholipase C (PLC), ultimately leading to an increase in intracellular calcium ion concentration. This increase in calcium is not only necessary but also critical for directed cell migration.
FPR activates multiple signaling pathways, triggering a chain reaction within cells, thereby affecting cell function and behavior.
The duality of immune response
Although the primary role of FPRs is to initiate immune responses upon infection, they may also promote immunosuppression in certain circumstances. For example, the roles played by FPRs in certain tumor microenvironments and their alterations during chronic inflammation highlight the dual nature of these receptors in various pathological conditions. Furthermore, activation of FPRs has been implicated in the development of neuropathologies, such as those seen in some amyloid diseases. SummaryPeptide receptor formation is not only crucial in immune responses, but also plays a complex role in immune regulation. From chemotaxis to cellular physiological responses, these receptors provide new insights into host defense mechanisms. However, as we discover more about the functions of these receptors and their potential therapeutic uses, we continue to ask ourselves an important question: How can the dual roles of FPRs be balanced to achieve optimal physiological effects during infection and immune regulatory challenges?
