FAK is a ubiquitously expressed nonreceptor tyrosine kinase that regulates several endothelial cell processes important for angiogenesis, including motility and proliferation. This work describes the differential roles of endothelial cell FAK phosphorylation at tyrosines-397 and -861 for tumor angiogenesis in vivo. Using immunofluorescence, the authors found that different nonphosphorylatable tyrosine mutations within endothelial cell FAK, namely Y397 and Y861, have different binding abilities to phosphorylated Src. While loss of FAK-Y397 phosphorylation impairs binding of FAK to p-Src, loss of FAK-Y861 phosphorylation does not affect binding to p-Src at focal adhesion sites as shown in this image. For details see article by Pedrosa and colleagues on page 4371.