A peptide derived from the Wiskott-Aldrich syndrome (WAS) protein-interacting protein (WIP) restores WAS protein level and actin cytoskeleton reorganization in lymphocytes from patients with WAS mutations that disrupt WIP binding.

BACKGROUND: The Wiskott-Aldrich syndrome (WAS) and X-linked thrombocytopenia (XLT) are caused by mutations in WAS, which encodes for WAS protein (WASP). The WASP-interacting protein (WIP) stabilizes WASP, as evidenced by severely decreased WASP levels in T cells from WIP-deficient mice. The majority of missense mutations in patients with WAS/XLT are located in the WIP-binding domain of WASP and might result in dissociation of the WASP-WIP complex and WASP degradation.

OBJECTIVE: To restore WASP levels and correct T-cell function in WAS/XLT patients with mutations in the WIP-binding domain of WASP.

METHODS: WIP, and a WIP-derived 41-amino acid-long peptide, which interacts with WASP and was designated nanoWIP (nWIP), were fused to enhanced green fluorescent protein and introduced by electroporation into EBV-transformed B cells, and by retroviral transduction into purified blood T cells from patients with WAS. WASP levels were measured by intracellular fluorescence-activated cell sorting staining. The actin cytoskeleton was visualized by intracellular phalloidin staining.

RESULTS: Introduction of WIP and nWIP restored WASP levels to normal in EBV-transformed B-cell lines from XLT patients with missense mutations in the WIP-binding domain of WASP and residual WASP levels, and corrected the defective spreading and pseudopodia formation of their T cells in response to immobilized anti-CD3.

CONCLUSION: A WASP-binding WIP-derived peptide stabilizes WASP in cells from XLT patients with missense mutations that disrupt WIP binding, and corrects their T-cell actin cytoskeleton defect. This may provide a novel therapeutic strategy for these patients.