Reactome | CD28 homodimer binds B7-1 homodimer

CD28 homodimer binds B7-1 homodimer

Stable Identifier

R-HSA-388811

Type

Reaction [binding]

Species

Homo sapiens

Compartment

plasma membrane

ReviewStatus

5/5

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CD28 binding to B7-1 on antigen-presenting cells (APCs) provides a crucial costimulatory signal that enhances T cell activation. This interaction modulates antigen recognition by T cells and ensures full activation in conjunction with T-cell receptor (TCR) engagement. Despite the homodimeric nature of CD28, it interacts with B7-1 in a manner that mimics a single binding site. The V-like domain of CD28 features the conserved MYPPPY motif within the CDR3-analogous loop, which is critical for the recognition and binding of its ligands. Both B7-1 and B7-2 interact with CD28 at overlapping, though non-identical, binding sites, contributing to nuanced modulation of T cell activation (Linsley et al. 1994, Truneh et al. 1996).
CTLA4 primarily affects CD28 costimulation by acting as a competitive inhibitor. CTLA-4 has a much higher affinity for these ligands compared to CD28. When CTLA-4 binds to B7-1 or B7-2, it prevents these ligands from interacting with CD28, thereby reducing the costimulatory signals that are crucial for T cell activation (van der Merwe et al. 1997).

Literature References

PubMed ID	Title	Journal	Year
8649453	Differential recognition by CD28 of its cognate counter receptors CD80 (B7.1) and B70 (B7.2): analysis by site directed mutagenesis Truneh, A, Reddy, M, Ryan, P, Lyn, SD, Eichman, C, Couez, D, Hurle, MR, Sekaly, RP, Olive, D, Sweet, R	Mol Immunol	1996
8609386	Interactions of CD80 and CD86 with CD28 and CTLA4 Ellis, JH, Burden, MN, Vinogradov, DV, Linge, C, Crowe, JS	J Immunol	1996