Real-time dynamics of emerging actin networks in cell-mimicking compartments

PLoS One. 2015 Mar 18;10(3):e0116521. doi: 10.1371/journal.pone.0116521. eCollection 2015.

Abstract

Understanding the cytoskeletal functionality and its relation to other cellular components and properties is a prominent question in biophysics. The dynamics of actin cytoskeleton and its polymorphic nature are indispensable for the proper functioning of living cells. Actin bundles are involved in cell motility, environmental exploration, intracellular transport and mechanical stability. Though the viscoelastic properties of actin-based structures have been extensively probed, the underlying microstructure dynamics, especially their disassembly, is not fully understood. In this article, we explore the rich dynamics and emergent properties exhibited by actin bundles within flow-free confinements using a microfluidic set-up and epifluorescence microscopy. After forming entangled actin filaments within cell-sized quasi two-dimensional confinements, we induce their bundling using three different fundamental mechanisms: counterion condensation, depletion interactions and specific protein-protein interactions. Intriguingly, long actin filaments form emerging networks of actin bundles via percolation leading to remarkable properties such as stress generation and spindle-like intermediate structures. Simultaneous sharing of filaments in different links of the network is an important parameter, as short filaments do not form networks but segregated clusters of bundles instead. We encounter a hierarchical process of bundling and its subsequent disassembly. Additionally, our study suggests that such percolated networks are likely to exist within living cells in a dynamic fashion. These observations render a perspective about differential cytoskeletal responses towards numerous stimuli.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / chemistry*
  • Actins / metabolism
  • Animals
  • Rabbits
  • Stress Fibers / chemistry*
  • Stress Fibers / metabolism

Substances

  • Actins

Grants and funding

SD and TP received financial support from the Swiss National Science Foundation, grant number SNF 200020_141270. Financial support from the Swiss Nanoscience Institute (SNI) is gratefully acknowledged. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.