. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 404 THE CYTOSKELETON. 1000 1500 2000 Time [sec] 3000 Figure 3. Rheology of vimentin networks disrupted by polyphosphoinositide lipids. Other phospholip- ids, such as phosphatidyl serine, phosphatidyl choline, and phosphatidyl inositol, had no significant effect on vimentin polymerization. in Figure 2 as a function of vimentin polymerization and concentration. Tlie time course is witii stopped flow measurements of vimentin polymerization (data not shown). This breakage phenomenon appears to be specific for vimenti
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 404 THE CYTOSKELETON. 1000 1500 2000 Time [sec] 3000 Figure 3. Rheology of vimentin networks disrupted by polyphosphoinositide lipids. Other phospholip- ids, such as phosphatidyl serine, phosphatidyl choline, and phosphatidyl inositol, had no significant effect on vimentin polymerization. in Figure 2 as a function of vimentin polymerization and concentration. Tlie time course is witii stopped flow measurements of vimentin polymerization (data not shown). This breakage phenomenon appears to be specific for vimentin, since no breakage is seen with microtubules in actin, or with actin in microtubules or fibrin (data not shown). Vimentin-phospholipid interactions The interaction of vimentin and phospholipids was measured by rheological methods and showed that poly- phosphoinositide lipids inhibit the formation of an elastic network. Inhibition was observed with PI(4)P and PI(4,5)P2, and to a lesser extent with PI (Fig. 3). Inhibition was not observed with PC or PS. These results are consis- tent with early studies by Perides et al. (1986) showing that phospholipid vesicles, especially those containing PIP and PlPn, inhibit vimentin polymerization and depo- lymerize preformed vimentin filaments. Conclusions Fluorescent actin filaments decrease in length in the presence of polymerizing vimentin. Filament breakage was not observed in other biopolymer systems, indicating that the interaction is specific. PIP and PIP: inhibit the polymerization of vimentin as measured by rheological methods. This evidence points to a specific interaction between vimentin and polyphos- phoinositide lipids. Acknowledgments The authors thank Jay Tang, Zeno Guttenburg, and Wolfgang Goldman for performing the kinetic stopped- flow measurements. This work was sponsored by the NIH grant AR38910 () and the National Science and Engineering Research Council of Canada (). Literature Cited Brown, K. D., and L.
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