WASF3 is a cytoskeletal regulatory protein that functions as a downstream effector of tyrosine kinase and small GTPase signaling, controlling actin filament polymerization and cell morphology 1. It operates as part of the WASF Regulatory Complex (WRC), which promotes Arp2/3 complex-mediated actin nucleation to drive lamellipodium and invadopodium formation 1. Beyond its canonical cytoskeletal role, WASF3 has emerged as a critical regulator in two distinct pathological contexts. In cancer, WASF3 expression correlates with metastatic potential across multiple tumor types including prostate, breast, and gastric cancers, functioning as a master scaffolding protein that integrates HER2/HER3 and hypoxia-inducible signaling to promote invasion and metastasis 2345. WASF3 knockdown significantly reduces tumor formation and metastasis while suppressing matrix metalloproteinase 9 6. Notably, WASF3 also disrupts mitochondrial function through mechanisms involving endoplasmic reticulum stress, impairing respiratory supercomplex assembly and reducing complex IV levels in skeletal muscle 7. WASF3 overexpression decreases exercise capacity in mice and elevated WASF3 levels associate with exercise intolerance in myalgic encephalomyelitis/chr13 fatigue syndrome patients 7. These findings suggest WASF3 represents a bifunctional protein linking cytoskeletal dynamics to bioenergetic dysfunction, with therapeutic potential as a target in both metastatic cancer and fatigue-associated disorders.