Regulation of Proximal TCR Signalling Requires Wiskott-Aldrich Syndrome Protein

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• Wiskott-Aldrich Syndrome protein (WASp) is an actin nucleation factor regulating cytoskeleton dynamics after T cell receptor (TCR) engagement.
• Proximal TCR signaling involves phosphorylation of proteins like CD3, Lck, and ZAP70, leading to signalosome formation, actin polymerization, and gene expression.
• The specific role of WASp in proximal TCR signaling remains largely uncharacterized.

Purpose of the Study:

• To investigate the role of WASp in proximal T cell receptor (TCR) signaling.
• To evaluate the impact of WASp knockout on TCR-induced signaling pathways in Jurkat T cells.

Main Methods:

• CRISPR-Cas9 gene editing was employed to generate WASp-knockout Jurkat T cells.
• TCR triggering was performed to assess signaling events.
• Actin polymerization, protein phosphorylation (CD3, Lck, ZAP70), protein recruitment to the TCR, and expression of activation markers (CD69, CD25) were analyzed.

Main Results:

• WASp-deficient Jurkat T cells showed impaired actin polymerization.
• TCR triggering in WASp-knockout cells resulted in reduced phosphorylation of CD3, Lck, and ZAP70.
• Recruitment of Lck and ZAP70 to the TCR was abolished, and CD69 and CD25 expression was decreased.

Conclusions:

• WASp is essential for proximal TCR signaling, not only for actin rearrangement.
• The absence of WASp disrupts the phosphorylation cascade and protein recruitment necessary for TCR signal transduction.
• These findings highlight a critical role for WASp in T cell activation pathways beyond its known function in cytoskeletal dynamics.