Editing Microtubule (section)

==Intracellular organization==

Microtubules are part of the [[cytoskeleton]], a structural network within the cell's [[cytoplasm]]. The roles of the microtubule cytoskeleton include mechanical support, organization of the cytoplasm, transport, motility and chromosome segregation. In developing neurons microtubules are known as [[neurotubule]]s,<ref name="Webster">{{Cite web |title=Medical Definition of Neurotubules |url=https://www.merriam-webster.com/medical/neurotubules |url-status=live |archive-url=https://web.archive.org/web/20180927050133/https://www.merriam-webster.com/medical/neurotubules |archive-date=2018-09-27 |access-date=2018-09-26 |website=www.merriam-webster.com |language=en}}</ref> and they can modulate the dynamics of [[actin]], another component of the cytoskeleton.<ref>{{Cite journal |vauthors=Zhao B, Meka DP, Scharrenberg R, König T, Schwanke B, Kobler O, Windhorst S, Kreutz MR, Mikhaylova M, Calderon de Anda F |date=August 2017 |title=Microtubules Modulate F-actin Dynamics during Neuronal Polarization |journal=Scientific Reports |volume=7 |issue=1 |page=9583 |bibcode=2017NatSR...7.9583Z |doi=10.1038/s41598-017-09832-8 |pmc=5575062 |pmid=28851982}}</ref> A microtubule is capable of growing and shrinking in order to generate force, and there are motor proteins such as kinesins and dynein that allow organelles and other cellular components (such as mRNA) to be carried along a microtubule, using specific adaptor proteins.<ref>{{cite journal | url=https://www.nature.com/articles/s41580-020-00320-y | doi=10.1038/s41580-020-00320-y | title=Sorting out microtubule-based transport | date=2021 | last1=Yildiz | first1=Ahmet | journal=Nature Reviews Molecular Cell Biology | volume=22 | issue=2 | page=73 | pmid=33288890 }}</ref><ref>{{cite journal | pmc=5411697 | date=2017 | last1=Barlan | first1=K. | last2=Gelfand | first2=V. I. | title=Microtubule-Based Transport and the Distribution, Tethering, and Organization of Organelles | journal=Cold Spring Harbor Perspectives in Biology | volume=9 | issue=5 | pages=a025817 | doi=10.1101/cshperspect.a025817 | pmid=28461574 }}</ref> This combination of roles makes microtubules important for organizing and moving intracellular constituents/cargo.

The organization of microtubules in the cell is cell-type specific.  In [[epithelia]], the minus-ends of the microtubule polymer are anchored near the site of cell-cell contact and organized along the apical-basal axis.  After nucleation, the minus-ends are released and then re-anchored in the periphery by factors such as [[ninein]] and [[PLEKHA7]].<ref>{{Cite journal |vauthors=Bartolini F, Gundersen GG |date=October 2006 |title=Generation of noncentrosomal microtubule arrays |journal=Journal of Cell Science |volume=119 |issue=Pt 20 |pages=4155–63 |doi=10.1242/jcs.03227 |pmid=17038542 |doi-access=free}}</ref>  In this manner, they can facilitate the transport of proteins, vesicles and organelles along the apical-basal axis of the cell.  In [[fibroblast]]s and other mesenchymal cell-types,  microtubules are anchored at the centrosome and radiate with their plus-ends outwards towards the cell periphery (as shown in the first figure).  In these cells, the microtubules play important roles in cell migration.  Moreover, the polarity of microtubules is acted upon by motor proteins, which organize many components of the cell, including the [[endoplasmic reticulum]] and the [[Golgi apparatus]].

[[File:FluorescentCells.jpg|thumb|right|Components of the [[eukaryotic]] cytoskeleton. [[Actin filaments]] are shown in red, [[microtubules]] are in green, and the [[cell nucleus|nuclei]] are in blue. The cytoskeleton provides the cell with an inner framework and enables it to move and change shape.]]