Glucocorticoids cause rapid dissociation of a T-cell-receptor-associated protein complex containing LCK and FYN

Area of Science:

• Immunology
• Molecular Biology
• Cell Signaling

Background:

• Glucocorticoids (GCs) exert rapid, nongenomic effects on immune cells, but the mechanisms are unclear.
• Lymphocyte-specific protein tyrosine kinase (LCK) and FYN oncogene related to SRC, FGR, YES (FYN) were previously implicated in GC-induced inhibition of T-cell receptor (TCR) signaling.

Purpose of the Study:

• To elucidate the molecular mechanism underlying GC-induced nongenomic inhibition of TCR signaling.
• To characterize the role of the GC receptor, LCK, FYN, and heat-shock protein 90 (HSP90) in TCR signaling complex formation and activation.

Main Methods:

• Utilized short interfering RNA (siRNA) to deplete GC receptor and HSP90 in cells.
• Investigated the composition and dynamics of the TCR-linked multiprotein complex.
• Assessed LCK/FYN activation and TCR signaling following GC treatment and siRNA transfection.

Main Results:

• The GC receptor is a component of a TCR-linked multiprotein complex with HSP90, LCK, and FYN, crucial for TCR-dependent LCK/FYN activation.
• Short-term GC treatment dissociates this complex, impairing TCR signaling by abrogating LCK/FYN activation.
• HSP90 depletion prevents complex assembly, mimicking GC effects on LCK/FYN activity.

Conclusions:

• Nongenomic immunosuppression by GCs results from the dissolution of membrane-bound GC receptor multiprotein complexes upon GC receptor ligation.
• This mechanism involves the disruption of TCR signaling complex integrity and subsequent inhibition of LCK/FYN activation.