Recruitment of Sprouty1 to immune synapse regulates T cell receptor signaling

Area of Science:

• Immunology
• Cell Signaling
• Molecular Biology

Background:

• T cell receptor (TCR) stimulation triggers both activation and negative regulation of T cells.
• Sprouty1, a known negative regulator of receptor tyrosine kinase signaling, is induced by TCR signals and inhibits TCR signaling in CD4+ T cells.

Purpose of the Study:

• To elucidate the mechanism by which Sprouty1 inhibits T cell signaling.
• To investigate Sprouty1's role in the T cell immune synapse and its interaction with TCR signaling components.

Main Methods:

• Overexpression of Sprouty1 in Jurkat T cells.
• Analysis of IL-2 transcription, AP-1, NFAT, and NF-kappaB activation.
• Immunofluorescence to track Sprouty1 translocation to the immune synapse.
• Co-immunoprecipitation to identify interacting signaling molecules.
• Western blotting to assess protein phosphorylation (e.g., LAT).
• Site-directed mutagenesis of Sprouty1.

Main Results:

• Sprouty1 overexpression inhibited TCR-induced IL-2 transcription and transcription factor activation (AP-1, NFAT, NF-kappaB).
• Sprouty1 translocated to the immune synapse upon TCR engagement in Jurkat and primary T cells.
• Sprouty1 interacted with LAT, PLC-gamma1, c-Cbl/Cbl-b, and HPK1 within the TCR signalosome.
• Sprouty1 inhibited LAT phosphorylation, leading to reduced MAPK activation and IL-2 production.
• A C-terminal deletion mutant of Sprouty1 lost its inhibitory function and failed to translocate to the immune synapse or interact with LAT.

Conclusions:

• Sprouty1 negatively regulates T cell signaling by interacting with proximal molecules in the immune synapse.
• TCR-induced Sprouty1 acts as a feedback mechanism to control T cell activation.
• Sprouty1's interaction with LAT is crucial for its inhibitory function and immune synapse localization.