Ishikawa R, Yamashiro S, Kohama K, Matsumura F
Department of Molecular Biology and Biochemistry, Nelson Laboratory, Busch Campus, Rutgers University, Piscataway, New Jersey 08854, USA.
J Biol Chem. 1998 Oct 9;273(41):26991-7. doi: 10.1074/jbc.273.41.26991.
Human fascin is an actin-bundling protein and is thought to play a role in the formation of microfilament bundles of microspikes and stress fibers in cultured cells. To explore the regulation of fascin-actin interaction, we have examined the effects of culture cell caldesmon and tropomyosin (TM) on actin binding activity of human fascin. Caldesmon alone or TM alone has little or no effect on the actin binding of fascin. However, caldesmon together with TM completely inhibits actin binding of human fascin. When calmodulin is added, the inhibition of fascin-actin interaction by caldesmon and TM becomes Ca2+ dependent because Ca2+/calmodulin blocks actin binding of caldesmon. Furthermore, as phosphorylation of caldesmon by cdc2 kinase inhibits actin binding of caldesmon, phosphorylation can also control actin binding of fascin in the presence of TM. As expected by the inhibition of fascin-actin binding, caldesmon coupled with TM also inhibits actin bundling activity of fascin. Whereas smooth muscle caldesmon alone or TM alone shows no effect, caldesmon together with TM completely inhibits actin bundling activity of fascin. This inhibition is again Ca2+ dependent when calmodulin is added to the system. These results suggest important roles for caldesmon and TM in the regulation of the function of human fascin.
人源丝束蛋白是一种肌动蛋白成束蛋白，被认为在培养细胞中微刺和应力纤维的微丝束形成过程中发挥作用。为了探究丝束蛋白与肌动蛋白相互作用的调控机制，我们研究了培养细胞中的钙调蛋白和原肌球蛋白（TM）对人源丝束蛋白肌动蛋白结合活性的影响。单独的钙调蛋白或单独的TM对丝束蛋白的肌动蛋白结合作用很小或没有影响。然而，钙调蛋白与TM共同作用时会完全抑制人源丝束蛋白的肌动蛋白结合。当添加钙调蛋白时，钙调蛋白和TM对丝束蛋白 - 肌动蛋白相互作用的抑制作用变得依赖于Ca2 +，因为Ca2 + /钙调蛋白会阻断钙调蛋白的肌动蛋白结合。此外，由于细胞周期蛋白依赖性激酶2（cdc2激酶）对钙调蛋白的磷酸化会抑制钙调蛋白的肌动蛋白结合，在存在TM的情况下，磷酸化也可以控制丝束蛋白的肌动蛋白结合。正如丝束蛋白 - 肌动蛋白结合受到抑制所预期的那样，钙调蛋白与TM结合也会抑制丝束蛋白的肌动蛋白成束活性。单独的平滑肌钙调蛋白或单独的TM没有作用，而钙调蛋白与TM共同作用时会完全抑制丝束蛋白的肌动蛋白成束活性。当向系统中添加钙调蛋白时，这种抑制作用同样依赖于Ca2 +。这些结果表明钙调蛋白和TM在调控人源丝束蛋白功能中发挥重要作用。
