CD45 functions as a signaling gatekeeper in T cells.

Area of Science:

• Immunology
• Cellular Signaling
• Biochemistry

Background:

• T cell activation relies on the protein tyrosine phosphatase CD45 to detect antigens.
• CD45 activates the Src family kinase Lck, essential for T cell receptor (TCR) complex phosphorylation.
• CD45 paradoxically also suppresses TCR signaling by dephosphorylating key motifs.

Purpose of the Study:

• Reconcile the dual activating and suppressing roles of CD45 in T cell receptor signaling.
• Investigate the regulatory axis of Csk and CD45 using computational and experimental approaches.
• Elucidate how CD45 tunes antigen discrimination through graded signaling outputs.

Main Methods:

• Utilized chemical and genetic perturbations of the Csk/CD45 regulatory axis.
• Employed computational analyses to model T cell signaling dynamics.
• Titrated Csk and CD45 activities to assess Lck activation and TCR-associated ζ-chain phosphorylation.

Main Results:

• CD45 suppresses ζ-chain phosphorylation and maintains a pool of active Lck.
• CD45's dual role interconnects TCR signaling activation and suppression for antigen discrimination.
• CD45 selectively suppressed antigen-independent or low-affinity antigen-induced signaling, but not high-affinity signaling.

Conclusions:

• CD45 functions as a critical signaling gatekeeper in T cells.
• CD45 enables graded signaling outputs and filters spurious or weak signaling events.
• This mechanism is vital for precise T cell antigen discrimination and response.