Cdc42/alpha2beta1 integrin/membrane type‐1 metalloproteinase complexes regulate endothelial lumen formation in 3D collagen matrices

Abstract

Endothelial cell (EC) lumen formation is a critical step during new blood vessel development either by vasculogenesis or angiogenesis. Our laboratory has previously shown that EC tube morphogenesis in 3D collagen matrices is regulated by the development and coalescence of intracellular vacuoles and lumens, and that integrins, Rho GTPases, and matrix metalloproteinases (MMPs) play a key role in this process. Here, we show that EC lumen formation in 3D collagen matrices requires a coordinated interaction by integrin alpha2beta1, the Rho GTPase Cdc42, and membrane type‐1 MMP (MT1‐MMP). Treatment of ECs with siRNAs targeting alpha2 integrin subunit, Cdc42, or MT1‐MMP blocks EC vacuole and lumen formation. We further demonstrate that these three molecules exist as a complex to regulate EC lumen formation and that a disruption of this complex results in blockade of EC lumen formation. Inhibition of protein kinase C or Src family kinases, which have been shown to regulate EC lumen formation, leads to disassembly of this complex thereby inhibiting EC lumen formation in 3D collagen matrices. Our findings reveal that tight coordination of Cdc42, integrin alpha2beta1, and MT1‐MMP controls signaling pathways necessary for EC lumen and tube formation in 3D matrices. A detailed examination is underway to identify and examine additional signaling molecules involved in this morphogenic response.