The Gab family of adaptor proteins function as molecular scaffolds that mediate protein recrutiment to RTKs (1–3). Cytokine/growth factor triggering of protein tyrosine kinase receptors (RTKs) initiates signaling cascades that progress to the nucleus where signals for activation, proliferation and differentiation occur (1–3). This scaffolding mechanism represents a critical link in cytokine/growth factor signaling routes. Gab1-3 contain pleckstrin homology and potential binding sites for SH2 and SH3 domain-containing proteins (1,4,5). The recruitment of signaling partners to Gab family members is phosphorylation dependent (1,4). Insulin receptor and EGF-receptor signaling are among the cascades that rely on Gab family members to elicit a nuclear response to an extracellular stimulus (6,7). The human Gab3 gene maps to chromosome Xq28 and encodes a 586 amino acid protein (5).