Research Centre of Biotechnology, Russian Academy of Sciences, 119071 Moscow, Russia.
Department of Biophysics, Faculty of Physics, Lomonosov Moscow State University, 119234 Moscow, Russia.
Int J Mol Sci. 2024 Jun 22;25(13):6873. doi: 10.3390/ijms25136873.
The actin cytoskeleton is one of the most important players in cell motility, adhesion, division, and functioning. The regulation of specific microfilament formation largely determines cellular functions. The main actin-binding protein in animal cells is tropomyosin (Tpm). The unique structural and functional diversity of microfilaments is achieved through the diversity of Tpm isoforms. In our work, we studied the properties of the cytoplasmic isoforms Tpm1.8 and Tpm1.9. The results showed that these isoforms are highly thermostable and differ in the stability of their central and -terminal fragments. The properties of these isoforms were largely determined by the 6th exons. Thus, the strength of the end-to-end interactions, as well as the affinity of the Tpm molecule for F-actin, differed between the Tpm1.8 and Tpm1.9 isoforms. They were determined by whether an alternative internal exon, 6a or 6b, was included in the Tpm isoform structure. The strong interactions of the Tpm1.8 and Tpm1.9 isoforms with F-actin led to the formation of rigid actin filaments, the stiffness of which was measured using an optical trap. It is quite possible that the structural and functional features of the Tpm isoforms largely determine the appearance of these isoforms in the rigid actin structures of the cell cortex.
肌动蛋白细胞骨架是细胞运动、黏附、分裂和功能的最重要的参与者之一。特定微丝形成的调节在很大程度上决定了细胞功能。动物细胞中的主要肌动蛋白结合蛋白是原肌球蛋白（Tpm）。微丝的独特结构和功能多样性是通过 Tpm 同工型的多样性实现的。在我们的工作中，我们研究了细胞质同工型 Tpm1.8 和 Tpm1.9 的特性。结果表明，这些同工型具有很高的热稳定性，并且它们的中心和-末端片段的稳定性不同。这些同工型的特性在很大程度上取决于第 6 个外显子。因此，Tpm1.8 和 Tpm1.9 同工型之间的末端到末端相互作用的强度以及 Tpm 分子对 F-肌动蛋白的亲和力不同。它们由 Tpm 同工型结构中是否包含替代的内部外显子 6a 或 6b 来决定。Tpm1.8 和 Tpm1.9 同工型与 F-肌动蛋白的强相互作用导致刚性肌动蛋白丝的形成，其刚性使用光阱进行测量。很有可能 Tpm 同工型的结构和功能特征在很大程度上决定了这些同工型在细胞皮质的刚性肌动蛋白结构中的出现。
