IgG receptor activity

Definition

Target type: molecularfunction

Combining with an immunoglobulin of an IgG isotype via the Fc region, and transmitting the signal from one side of the membrane to the other to initiate a change in cell activity. [GOC:add, GOC:signaling, ISBN:0781735149]

IgG receptor activity involves the recognition and binding of immunoglobulin G (IgG) antibodies. IgG antibodies are a major class of antibodies in the immune system, and they play a crucial role in neutralizing pathogens, opsonizing cells for phagocytosis, and activating complement. IgG receptor activity is mediated by specific cell surface receptors, known as Fcγ receptors (FcγRs), which are expressed on various immune cells such as macrophages, neutrophils, B cells, natural killer (NK) cells, and dendritic cells.

FcγRs are transmembrane proteins with an extracellular domain that binds to the Fc region of IgG antibodies. Binding of IgG to FcγRs triggers a cascade of intracellular signaling events that ultimately lead to the activation of immune effector functions.

The molecular function of IgG receptor activity can be summarized as follows:

- **Recognition and binding of IgG antibodies:** FcγRs specifically bind to the Fc region of IgG antibodies, which is the constant region of the antibody molecule. This binding is highly specific and is mediated by interactions between amino acid residues on the FcγR and the Fc region of IgG.
- **Signal transduction:** Binding of IgG to FcγRs triggers a cascade of intracellular signaling events. These events involve the activation of various signaling molecules, such as tyrosine kinases, phosphatases, and adaptor proteins.
- **Activation of immune effector functions:** The intracellular signaling triggered by IgG binding to FcγRs leads to the activation of various immune effector functions, including:

- **Phagocytosis:** FcγRs on phagocytic cells, such as macrophages and neutrophils, mediate the engulfment and destruction of pathogens opsonized with IgG antibodies.
- **Antibody-dependent cell-mediated cytotoxicity (ADCC):** FcγRs on NK cells and other cytotoxic cells mediate the killing of target cells coated with IgG antibodies.
- **Complement activation:** FcγRs can also activate the complement system, a cascade of proteins that ultimately leads to the lysis of target cells.
- **Antigen presentation:** FcγRs on dendritic cells can bind to IgG-antigen complexes and deliver these complexes to the MHC II pathway for antigen presentation to T cells.

Overall, IgG receptor activity is a critical process in the immune system that allows immune cells to recognize and respond to pathogens and other foreign antigens bound by IgG antibodies. This process is essential for the effective clearance of infections and the maintenance of immune homeostasis.'
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Proteins (1)

Compounds (2)