1. Centre for Cell Signalling, Institute of Cancer, Queen Mary, University of London, Charterhouse Square, London EC1M 6BQ, UK
2. Vascular Biology Laboratory, Cancer Research UK London Research Institute, 44 Lincoln's Inn Fields, London WC2A 3PX, UK
3. King's College London, Randall Division of Cell and Molecular Biophysics, New Hunt's House, Guy's Campus, London SE1 1UL, UK
4. Gene Targeting Laboratory, The Institute for Stem Cell Research, University of Edinburgh, West Mains Road, Edinburgh EH9 3JQ, UK
5. Department of Cell Biology, Institute of Ophthalmology, University College London, London EC1V 9EL, UK

Correspondence to: Holger Gerhardt²Bart Vanhaesebroeck¹ Correspondence and requests for materials should be addressed to H.G. (Email: Holger.gerhardt@cancer.org.uk) or B.V. (Email: bart.vanh@qmul.ac.uk).

Abstract

Phosphoinositide 3-kinases (PI3Ks) signal downstream of multiple cell-surface receptor types. Class IA PI3K isoforms¹ couple to tyrosine kinases and consist of a p110 catalytic subunit (p110, p110 or p110), constitutively bound to one of five distinct p85 regulatory subunits. PI3Ks have been implicated in angiogenesis^{2, 3, 4, 5}, but little is known about potential selectivity among the PI3K isoforms and their mechanism of action in endothelial cells during angiogenesis in vivo. Here we show that only p110 activity is essential for vascular development. Ubiquitous or endothelial cell-specific inactivation of p110 led to embryonic lethality at mid-gestation because of severe defects in angiogenic sprouting and vascular remodelling. p110 exerts this critical endothelial cell-autonomous function by regulating endothelial cell migration through the small GTPase RhoA. p110 activity is particularly high in endothelial cells and preferentially induced by tyrosine kinase ligands (such as vascular endothelial growth factor (VEGF)-A). In contrast, p110 in endothelial cells signals downstream of G-protein-coupled receptor (GPCR) ligands such as SDF-1, whereas p110 is expressed at low level and contributes only minimally to PI3K activity in endothelial cells. These results provide the first in vivo evidence for p110-isoform selectivity in endothelial PI3K signalling during angiogenesis.

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