Tie1

Tie1 is an endothelial receptor tyrosine kinase required for vascular endothelial integrity and survival during blood vessel formation^[1][2]. Mechanistically, Tie1 regulates the angiopoietin-Tie2 signaling pathway, where angiogenic endothelial cells use Tie1 to shape tip-cell behavior by reducing Tie2 surface presentation, while remodeling stalk cells use Tie1 to sustain Tie2 signaling^[3]. In inflammatory vascular remodeling, Tie1 controls angiopoietin function and supports Ang1- and Ang2-dependent Tie2 activation, linking Tie1 to vessel leakage and inflammation models^[4]. In tumor models, endothelial Tie1 deletion inhibits tumor angiogenesis and growth, and Tie1-mediated angiogenesis and vascular abnormalization promote tumor progression and metastasis^[5][6]. Compared with the related Tie2/TEK receptor, Tie1 acts as an orphan, context-dependent regulator rather than a direct angiopoietin receptor, making Tie1-Tie2 coordination central to experimental study design^[3][4]. For applications, Tie1-targeting nanobodies and function-blocking antibodies have inhibited endothelial angiogenesis, tumor cell migration, extravasation, and metastasis in preclinical systems^[7][8].