J028024 ストレスファイバから細胞核への直接的張力伝達に関する研究 : ストレスファイバと核膜の結合状態の影響

Abstract

Actin stress fibers (SFs) play important roles in cellular mechanotransduction and regulation of various cellular functions. SFs generate internal tension and contribute to physical interactions between cells and extracellular matrices. We recently found in vascular smooth muscle cells (SMCs) that the dorsal SFs running across the top surface of the nucleus have a mechanical interaction with the cell nucleus and their internal tension is transmitted directly to the nucleus. However, the effects of contact conditions between SFs and nucleus on their force transmission processes are unclear at this stage. In this study, we investigated the contact conditions between SFs and the nucleus using a laboratory-made UV laser nanoscissor. Firstly, we classified the dorsal SFs of SMCs into two types: one had line-like concentrations of intranuclear DNA along the dorsal SFs which may be due to the large compressive forces generated by the SFs (pressing SF), and the other did not have such concentrations of intranuclear DNA (attaching SF). We then cut these SFs by the laser to release their pretension, and observed the dynamic behaviour of nuclei. Following SF dissection, significant nuclear displacement and a decrease of nuclear area were observed in the pressing SF than in the attaching SF. This may indicate that SFs pressing strongly nuclear surface firmly attach to the nuclear membrane. The internal tension of the pressing SFs may be transmitted more efficiently than the attaching SFs to the nucleus, inducing conformational changes of intranuclear DNA.