Fig. 7. Model of paxillin involvement in the induction of microtubule catastrophe at adhesion sites. In control cells: (1) Paxillin (light blue) binds to adhesion sites (blue) through LIM2-LIM3 domains. Catastrophe factor (`Cat F', red box) binds to paxillin through sites other than LIM2-LIM3 domains and in this way is enriched at adhesion sites. (2A) When a microtubule (green) approaches a focal adhesion, the catastrophe factor associated with paxillin induces microtubule catastrophe (red star) and depolymerization (green arrow). Alternatively (2B), when a microtubule (green) approaches a focal adhesion, the catastrophe factor associated with paxillin activates microtubule-associated catastrophe-inducing factor (`CIF', magenta box) to induce microtubule catastrophe (magenta star) and depolymerization (green arrow). In LIM2-LIM3-injected cells (3), exogenous LIM2-LIM3 (light blue) binds to the adhesion site and replaces full-length paxillin. The catastrophe factor cannot bind to the LIM2-LIM3 mutant protein and is excluded from adhesion sites. (4) When a microtubule approaches the focal adhesion, it does not undergo catastrophe and continues to polymerize (green arrow) because catastrophe factor is absent or not activated at the adhesion site.