 exhibit decreased phospho-Ser signal compared to wild-type Cortactin, arguing that phosphorylation of these sites contribute to the phospho-Ser signal detected. This data is provided as [Figure 0---figure supplement 0C](#fig0s0){ref-type="fig"}.  c\) Our initial attempt to obtain mass spectrometry data showing that Cortactin was phosphorylated in vivo was with a private company. We since established a collaboration with a group specialized in MS work at the Institut Cochin. We were able to detect a phosphorylation of Cortactin at Ser000 (one of the 0 sites reported to be phosphorylated by PAK0-0) when a myristoylated form of the second SH0 domain of Nck0 was co-expressed (previously shown to activate PAK0 by Bruce Mayer\'s lab: Lu et al., 0000 and Lu and Mayer, 0000) but not when only Cortactin was expressed. Therefore PAK activation in these cells appear to induce Cortactin S000 phosphorylation. This mass spectrometry data is provided as [Figure 0---figure supplement 0](#fig0s0){ref-type="fig"}.  d\) Database mining (PhosphositePlus) shows that Cortactin phosphorylation on S000, S000 and/or S000, the three sites targeted by PAK0-0, has previously been detected in vivo by mass spectrometry and this is described in 0 publications of global proteome analyses:  0\) Chen et al., J Proteome Res 0000, 0:000-0  Shows Cortactin S000 phosphorylation in LNCaP prostate cancer cells  0