www.landesbioscience.com Cell Cycle 3709

The vasculature plays a crucial role in normal physiology, supplying oxygen and nutrients, as well as maintaining a semi-permeable barrier between tissues and the bloodstream. Endothelial cells (ECs), which form the innermost lining of blood vessels, are critical players in vascular function, by regulating the transport of solutes and immune cells into and out of the bloodstream, regulating vasoreactivity, and maintaining the vasculature in an anti-thrombotic state. Disruption of endothelial homeostasis is a feature of a variety of pathological conditions, including cancer, atherosclerosis, diabetes mellitus, and inflammatory arthritis.1 Endothelial function is regulated, in part, by a variety of soluble, pro-angiogenic growth factors, including the angiopoietins. Angiopoietin-1 (Angpt1), the primary agonistic angiopoietin ligand, signals through the endothelial receptor tyrosine kinase Tie2 to support functions including EC survival and vascular stability.2 Angiopoietin-2 (Angpt2) functions as a context-dependent Tie2 antagonist or partial agonist and is highly expressed by ECs in tissues undergoing vascular remodeling or at sites of inflammation.3 A recent study from our laboratory has demonstrated a crucial role for the Abelson (Abl) family of non-receptor tyrosine kinases in vascular function in vivo, as well as in the regulation of Angpt1/ Tie2 signaling and Angpt1-mediated EC survival.4 The Abl kinase family include