FIGURE 4.

ArgBP2 expression increases the level of actinin on stress fibers and increases the cross-linking and organization of the actomyosin network. COS-7 (A), HeLa (B), and U2-OS (C) cells were stained for endogenous α-actinin and for endogenous ArgBP2 in A and B or GFP-ArgbP2 in C. The detection of endogenous ArgBP2 in COS-7 (A) and HeLa (B) correlates with more α-actinin present along the actin stress fibers. C, U2-OS cells stably expressing GFP-ArgBP2 also increased the α-actinin recruitment to the actin stress fibers. Yellow plus signs denote ArgBP2-positive cells and blue dots denote ArgBP2-negative cells. The fluorescent signal was inverted (white to black) for greater clarity. The increase in intensity of α-actinin at these puncta was detected by selecting an identically sized region from ArgBP2 positive and negative cells. The background was subtracted for these regions in ImageJ and the signal intensity was quantified and plotted (D). These regions were then thresholded and objects were separated by a watershed algorithm in ImageJ. The area of the objects were calculated and plotted in E. Both graphs display one S.D.