peptide antigen transport

Definition

Target type: biologicalprocess

The directed movement of a peptide antigen into, out of or within a cell, or between cells, by means of some agent such as a transporter or pore. The peptide antigen is typically, but not always, processed from an endogenous or exogenous protein. [GOC:add, ISBN:0781735149, PMID:15771591]

Peptide antigen transport is a crucial process in the adaptive immune response, enabling the presentation of foreign antigens to T cells. This process involves several steps:

1. **Protein Degradation:** Antigens, such as viral proteins or bacterial toxins, are degraded into smaller peptides within the cytoplasm by proteasomes. These are large protein complexes that break down proteins into smaller peptides.

2. **TAP Translocation:** The generated peptides are then transported into the endoplasmic reticulum (ER) lumen by the transporter associated with antigen processing (TAP) complex. TAP is a heterodimer composed of two transmembrane proteins, TAP1 and TAP2. This complex recognizes and translocates peptides that are typically 8-16 amino acids long.

3. **Loading onto MHC Class I Molecules:** Once inside the ER lumen, peptides bind to MHC class I molecules. MHC class I molecules are specialized proteins that present antigens to cytotoxic T cells. These molecules consist of a heavy chain and a light chain (beta-2 microglobulin). The peptide-MHC complex then folds and is transported to the cell surface.

4. **Cell Surface Expression:** The peptide-MHC complex is transported to the cell surface via the Golgi apparatus. This complex is now displayed on the cell surface, making it accessible for recognition by cytotoxic T cells.

5. **T Cell Recognition:** Cytotoxic T cells express T cell receptors (TCRs) that specifically recognize peptide-MHC complexes. If the TCR recognizes a foreign peptide, it activates the cytotoxic T cell to destroy the infected or cancerous cell.

This process ensures that only peptides derived from intracellular proteins are presented to T cells, providing a robust immune response against intracellular pathogens and cancer cells.'
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Proteins (2)

Compounds (5)