Movie 4

Differential dynamics of nascent adhesions in cells displaying distinct protrusion phenotypes. B16-F1 control and Lpd KO cells were transfected with EGFP-paxillin, and subjected to time-lapse microscopy during migration on laminin using fluorescence and phase contrast channels, as indicated. A representative B16-F1 control (left panel) is displayed as example for the smooth protrusion phenotype, whereas the middle and right panels show representative examples for nascent adhesion dynamics typically found in protruding cells exhibiting the intermediate and chaotic phenotype, respectively. Phase contrast images (bottom) allow the correlation of distinct protrusion phenotypes with differential adhesion dynamics. The smooth protrusion phenotype is commonly associated with generation of multiple, nascent adhesions, continuously developing distally from previous sets of adhesions during continuous protrusion. Subsets of each population of nascent adhesions then are continuously elongated and developed into mature adhesions. In the intermediate phenotype (middle panels), nascent adhesions are less continuously formed and concentrated at the rear edge of the lamellipodium, frequently coincident with sites of active membrane ruffling. The chaotic protrusion phenotype with its commonly collapsing lamellipodia (right panels) is characterised instead by strongly reduced frequency of nascent adhesion formation.