Figure 4. TM domain separation is required for FA formation, actin fiber organization, FAK activation and recruitment to FA sites in outside-in signaling.

(A) Clasping of TM domains ablated FA formation and disrupted actin filaments organization. Note that α truncation led to an even distribution of FAs around adherent cells. (B) Treatment with 1mM DTT largely restored cell spreading and FA assembly. Green: focal adhesions (labeled with anti-vinculin antibody); Red: actin filaments (labeled with TRITC-conjugated Phalloidin). White bar: 10μm. (C) Activated FAK (FAKpY397) was recruited normally to FAs in WT (B1) and the α-truncated mutant (B3), but recruitment was abolished by clasping the TM domains (B2 and B4). (D) Treatment with 1mM DTT restored recruitment of phosphorylated FAK to FAs. Green: FAKpY397; Red: actin filaments; Blue: FA marker vinculin. White bar: 10μm.