Intracellular Memory of Stress Fiber Orientation: Focal Adhesions Store It and Microtubules Erase It During Disassembly–Reassembly Process of Stress Fibers

Abstract

Stress fibers (SFs) play essential roles in various cellular functions, and they reorganized in response to changes in mechanical environment. Recently, we noticed that the SF networks reappeared following their temporal disruption with cytochalasin D looked similar to those before disruption in rat aortic smooth muscle cells (SMCs). This indicates that the cells may have a memory of SF orientation. The aim of this study was to clarify the mechanism of the memory focusing on the effects of microtubules (MTs) and focal adhesions (FAs) during the reorganization process of SFs. Firstly, we preconditioned the cells with cyclic stretch to make their SFs align in a uniform direction. After cyclic stretching, we depolymerized SFs completely with cytochalasin D, and let them repolymerize in the drug-free medium. To investigate the effects of MTs during the SF repolymerization, we depolymerized MTs. FAs were observed with a surface reflective interference contrast microscopy. In the presence of MTs, repolymerized SFs were randomly orientated with newly formed FAs. In contrast, in the absence of MTs, FAs were not destroyed and the SF alignment was conserved. These indicate that FAs might store the memory of SF alignment while MTs may erase it.