Functional analysis of the strategic role of Ig-like domain 24 of filamin C

丝状蛋白C （Filamin C, FLNc）是一种大型细胞骨架蛋白，直接与f -肌动蛋白和多种功能多样的细胞蛋白结合，表明它是一种多功能适配蛋白。FLNc在横纹肌组织中的关键作用通过观察人类FLNc基因突变引起临床不同组的家族性和散发性肌病和心肌病而得到强调。FLNc的肌动蛋白丝交联活性是基于二聚体的形成，这是由其ig -样结构域24介导的。此外，FLNc的这个非常c端结构域，包含至少四个响应机械应力的磷酸化位点，也参与与小gtp酶、肌聚糖和HSPB7的相互作用。为了详细研究这一战略性结构域在细胞、分子和组织水平上的功能作用，我们在横切肌组织中培育了缺乏igg样结构域24的FLNc外显子47-48特异性敲除小鼠，并构建了含有磷酸体突变体的FLNc cDNA全长构建体，以及缺乏igg样结构域24的cDNA。使用多种方法，我们将解决以下关键问题：i) FLNc中igg样结构域24的缺乏如何影响机械应力下骨骼肌和心肌组织的结构和功能？ii)缺乏FLNc的igg样结构域24是否会损害FLNc相互作用组，特别是强调细胞信号传导、蛋白质稳态机制和细胞骨架相关附着位点？iii) igg样结构域24中位点特异性磷酸化的分子和细胞影响是什么？iv)直接分析活细胞中FLNc的力学敏感性。该项目将为FLNc及其igg样结构域24在细胞信号传导、机械传感和保护以及正常和患病横纹肌蛋白稳态中的功能作用提供新的和更深入的见解。

Filamin C (FLNc) is a large cytoskeletal protein directly binding to F-actin and a plethora of cellular proteins of great functional diversity, indicating that it serves as a multifunctional adapter protein. The pivotal role of FLNc in striated muscle tissue is highlighted by the observation that mutations of the human FLNC gene cause a clinically diverse group of familial and sporadic myopathies and cardiomyopathies. The actin filament-crosslinking activity of FLNc is based on dimer formation, which is mediated by its Ig-like domain 24. Moreover, this very C-terminal domain of FLNc, which contains at least four phosphorylation sites responsive to mechanical stress, is also involved in interactions with small GTPases, sarcoglycans and HSPB7. To address the functional role of this strategic domain at the cellular, molecular and tissue level in detail, we newly generated FLNc exon 47-48-specific knock-out mice lacking the Ig-like domain 24 in striated muscle tissue as well as full length FLNc cDNA constructs containing phosphosite mutants, as well as a cDNA lacking Ig-like domain 24. Using a multi-method approach, we will address the following key questions: i) How does the lack of Ig-like domain 24 of FLNc impact the structure and function of skeletal and cardiac muscle tissues under mechanical stress? ii) Does the lack of Ig-like domain 24 of FLNc impair the FLNc interactome, with special emphasis on cell signaling, the protein homeostasis machinery and cytoskeleton-associated attachment sites? iii) What is the molecular and cellular impact of site-specific phosphorylations in Ig-like domain 24? iv) Direct analysis of mechanosensitive properties of FLNc in living cells. This project will provide new and deeper insights into the functional role of FLNc and its Ig-like domain 24 in the context of cell signaling, mechanosensing and –protection, as well as protein homeostasis in normal and diseased striated muscle.