Editing Cytoskeleton (section)

== The cytoskeleton and cell mechanics ==
The cytoskeleton is a highly anisotropic and dynamic network, constantly remodeling itself in response to the changing cellular microenvironment. The network influences cell mechanics and dynamics by differentially polymerizing and depolymerizing its constituent filaments (primarily actin and myosin, but microtubules and intermediate filaments also play a role).<ref name="Chen 3285–3292">{{Cite journal |last=Chen |first=Christopher S. |date=2008-10-15 |title=Mechanotransduction – a field pulling together? |url=https://journals.biologists.com/jcs/article/121/20/3285/35315/Mechanotransduction-a-field-pulling-together |journal=Journal of Cell Science |language=en |volume=121 |issue=20 |pages=3285–3292 |doi=10.1242/jcs.023507 |pmid=18843115 |s2cid=1287523 |issn=1477-9137}}</ref> This generates forces, which play an important role in informing the cell of its microenvironment. Specifically, forces such as tension, stiffness, and shear forces have all been shown to influence cell fate, differentiation, migration, and motility.<ref name="Chen 3285–3292"/> Through a process called “mechanotransduction,” the cell remodels its cytoskeleton to sense and respond to these forces.

[[Mechanotransduction]] relies heavily on [[focal adhesions]], which essentially connect the intracellular cytoskeleton with the [[extracellular matrix]] (ECM). Through focal adhesions, the cell is able to integrate extracellular forces into intracellular ones as the proteins present at focal adhesions undergo conformational changes to initiate signaling cascades. Proteins such as focal adhesion kinase (FAK) and Src have been shown to transduce force signals in response to cellular activities such as proliferation and differentiation, and are hypothesized to be key sensors in the mechanotransduction pathway.<ref name="Mechanisms of Mechanotransduction">{{Cite journal |last1=Orr |first1=A. Wayne |last2=Helmke |first2=Brian P. |last3=Blackman |first3=Brett R. |last4=Schwartz |first4=Martin A. |date=January 2006 |title=Mechanisms of Mechanotransduction |journal=Developmental Cell |language=en |volume=10 |issue=1 |pages=11–20 |doi=10.1016/j.devcel.2005.12.006|pmid=16399074 |doi-access=free }}</ref> As a result of mechanotransduction, the cytoskeleton changes its composition and/or orientation to accommodate the force stimulus and ensure the cell responds accordingly.

The cytoskeleton changes the mechanics of the cell in response to detected forces. For example, increasing tension within the plasma membrane makes it more likely that ion channels will open, which increases ion conductance and makes cellular change ion influx or efflux much more likely.<ref name="Mechanisms of Mechanotransduction"/> Moreover, the mechanical properties of cells determine how far and where, directionally, a force will propagate throughout the cell and how it will change cell dynamics.<ref>{{Cite journal |last1=Janmey |first1=Paul A. |last2=McCulloch |first2=Christopher A. |date=2007-08-15 |title=Cell Mechanics: Integrating Cell Responses to Mechanical Stimuli |url=http://www.annualreviews.org/doi/10.1146/annurev.bioeng.9.060906.151927 |journal=Annual Review of Biomedical Engineering |language=en |volume=9 |issue=1 |pages=1–34 |doi=10.1146/annurev.bioeng.9.060906.151927 |pmid=17461730 |issn=1523-9829}}</ref> A membrane protein that is not closely coupled to the cytoskeleton, for instance, will not produce a significant effect on the cortical actin network if it is subjected to a specifically directed force. However, membrane proteins that are more closely associated with the cytoskeleton will induce a more significant response.<ref name="Mechanisms of Mechanotransduction"/> In this way, the anisotropy of the cytoskeleton serves to more keenly direct cell responses to intra or extracellular signals.