Induction of cortical oscillations in spreading cells by depolymerization of microtubules

Abstract

Actomyosin-based cortical contractility is a common feature of eukaryotic cells but the capability to produce rhythmic contractions is found in only a few types such as cardiomyocytes. Mechanisms responsible for the acquisition of this capability remain largely unknown. Rhythmic contractility can be induced in non-muscle cells by microtubule depolymerization. Spreading epithelial cells and fibroblasts in which microtubules were depolymerized with nocodazole or colcemid underwent rhythmic oscillations of the body that lasted for several hours before the cells acquired a stable, flattened shape. By contrast, control cells spread and flattened into discoid shapes in a smooth and regular manner. Quantitative analysis of the oscillations showed that they have a period of about 50 seconds. The kinase inhibitors, HA 1077 and H7, and the more specific rho-kinase inhibitor, Y 27632, caused the oscillations to immediately cease and the cells to become flat. Transient increases in cytoplasmic calcium preceded the contractile phase of the oscillations. Wrinkle formation by cells plated on elastic substrata indicated that the contractility of colcemid-treated cells increased in comparison to controls but was drastically decreased after HA 1077 addition. These data suggest that an intact microtubular system normally prevents pulsations by moderating excessive rho-mediated actin myosin contractility. Possible mechanistic interactions between rho-mediated and calcium activated contractile pathways that could produce morphological oscillations are discussed.

Spontaneous phosphoinositide 3-kinase signaling dynamics drive spreading and random migration of fibroblasts

“…The transient protrusion-retraction events sometimes appear to be non-random, firing in a radial pattern around the contact area. It would be interesting to investigate whether or not these dynamics seen by TIRF are related to previous observations that nocodazole induces orbital oscillations of the nucleus and of membrane blebs in spreading cells (Cuvelier et al, 2007;Pletjushkina et al, 2001). Microtubules have several roles in cell migration, including the local repression of contractility and maturation of focal adhesions near the leading edge (Small and Kaverina, 2003).…”

Real-time electrical measurement of L929 cellular spontaneous and synchronous oscillation

“…It has been reported that oscillation of nonmuscle L929 fibroblast cells can be induced through microtubule depolarization using nocodazole treatment. 13 It is also known that periodic and rhythmic oscillations are a special characteristic of a few cell types such as cardiomyocytes and astrocytes. 5,14 Interestingly, the present research observed spontaneous and rhythmic oscillation of nonmuscle fibroblast cells through continuous real-time monitoring of cellular behavior using an ECIS system.…”

Active gels as a description of the actin‐myosin cytoskeleton

“…The cortical actin layer can therefore be considered as an active gel. The mechanical properties of this gel have a strong influence on the morphology of cells and in particular on some shape instabilities of cells such as blebbing or spontaneous oscillations (Paluch et al, 2005;Pletjushkina et al, 2001). Recent experiments in Salbreux et al (2007) show that when fibroblasts do not adhere, they can spontaneously oscillate.…”