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Fig. 12. Role of phosphorylation sites on focal adhesion kinetics. We measured the rate of formation of focal adhesion sites in Dictyostelium strains transformed with the A15/pax-gfppaxB-GFP construct and compared this with the kinetics of formation of actin-rich spots and paxB– mutant mutants in which the potential JNK phosphorylation site has been mutated to alanine (S192A) or aspartate (S192D) respectively (see Materials and Methods for details on measurements). Curves were aligned so that the half-maximal increase in fluorescence intensity occurred at t=0 seconds, the number of adhesion sites measured per strain is indicated in the legend. The results clearly show that the kinetics of the focal adhesion sites differ from that of the actin spots. Their rate of formation is slower and they persist longer than the actin spots. There was no significant difference between the rate of formation between wild type and mutant paxillin. The total lifetime of the focal adhesion sites is more difficult to determine, since most sites disassemble when they reach the end of the cells. The lifetime and possibly rate of disassembly are therefore mostly determined by the movement speed of the cells.
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