Negative feedback loop in T-cell activation through MAPK-catalyzed threonine phosphorylation of LAT

Area of Science:

• Cellular Biology
• Immunology
• Molecular Signaling

Background:

• Mitogen-activated protein kinase (MAPK) cascades regulate critical cellular processes like proliferation, differentiation, and apoptosis.
• Understanding MAPK substrates is crucial for deciphering complex cellular signaling pathways.

Purpose of the Study:

• To develop a method for identifying in vivo MAPK substrates in mammalian cells.
• To identify novel targets of MAPKs involved in T-cell activation.

Main Methods:

• Development of an expression screening method to detect in vivo MAPK substrates.
• Identification of linker for activation of T cells (LAT) as a direct MAPK target.
• Phosphorylation site analysis of LAT at Thr 155 by ERK.

Main Results:

• Linker for activation of T cells (LAT), a key T-cell adapter protein, was identified as an in vivo MAPK substrate.
• ERK phosphorylates LAT at Threonine 155 (Thr 155) upon T-cell receptor stimulation.
• Phosphorylation of LAT at Thr 155 impairs the recruitment of PLCgamma1 and SLP76, attenuating downstream signaling events including calcium mobilization and further ERK activation.

Conclusions:

• MAPK signaling plays a role in a negative feedback loop during T-cell activation.
• Threonine phosphorylation of LAT by MAPKs represents a novel regulatory mechanism in T-cell signaling.
• This finding provides new insights into the intricate regulation of immune responses.