Lindberg Uno, Schutt Clarence E, Goldman Robert D, Nyåkern-Meazza Maria, Hillberg Louise, Rathje Li-Sophie Zhao, Grenklo Staffan
Karolinska Institutet, Department of Microbiology, Tumor Biology and Cell Biology, Nobels vig 16, SE 171 77 Stockholm, Sweden.
Adv Exp Med Biol. 2008;644:223-31. doi: 10.1007/978-0-387-85766-4_17.
The state of actin depends intimately on its interaction partners in eukaryotic cells. Classically, the cooperative force-generating acto-myosin couple is turned off and on by the calcium-dependent binding and release of tropomyosin molecules. The situation with nonmuscle cells appears to be much more complicated, with tropomyosin isoforms regulating the kinds of tension-producing and stress-bearing structures formed of actin filaments. The polymerization of even the shortest gelsolin-capped filaments is efficiently promoted by the binding of tropomyosin, for example, a process that might occur all the way out to the leading edges of advancing cells. Recently, multimers of tropomyosin have been discovered that appear to be assembly intermediates, formed from identical tropomyosin molecules, which act as ready pools of tropomyosin during the catalytic formation of lamellipodia and filopodia. Remarkably, these multimers apparently reform during the disassembly of cellular actin-containing structures. The existence of these recyclable, tropomyosin isoform-specific structures suggests how cells prevent nonproductive association of non-identical, but closely similar, tropomyosin isoforms.
在真核细胞中，肌动蛋白的状态与其相互作用伙伴密切相关。传统上，协同产生力的肌动蛋白-肌球蛋白偶联通过原肌球蛋白分子依赖钙的结合和释放来开启和关闭。非肌肉细胞的情况似乎要复杂得多，原肌球蛋白异构体调节由肌动蛋白丝形成的产生张力和承受压力的结构类型。例如，原肌球蛋白的结合能有效促进即使是最短的凝溶胶蛋白封端细丝的聚合，这一过程可能一直发生在前进细胞的前沿。最近，发现了原肌球蛋白多聚体，它们似乎是组装中间体，由相同的原肌球蛋白分子形成，在片状伪足和丝状伪足的催化形成过程中作为原肌球蛋白的备用库。值得注意的是，这些多聚体显然在含细胞肌动蛋白结构的解体过程中重新形成。这些可循环利用的、原肌球蛋白异构体特异性结构的存在表明了细胞如何防止不同但非常相似的原肌球蛋白异构体发生非生产性结合。
