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Cell cortex

F-actin distribution in the cell cortex as shown by rhodamine phalloidin staining of HeLa cells that constitutively express Histone H2B-GFP to mark chromosomes. F-actin is thus red, while Histone H2B is displayed in green. The left-hand cell is in mitosis, as demonstrated by chromosome condensation, while the right-hand cell is in interphase (as determined by intact cell nucleus) in a suspended state. In both cases, F-actin is enriched around the cell periphery. Scale bar: 10 micrometers.

The cell cortex, also known as the actin cortex, cortical cytoskeleton or actomyosin cortex, is a specialized layer of cytoplasmic proteins on the inner face of the cell membrane. It functions as a modulator of membrane behavior and cell surface properties.[1][2][3] In most eukaryotic cells lacking a cell wall, the cortex is an actin-rich network consisting of F-actin filaments, myosin motors, and actin-binding proteins.[4][5] The actomyosin cortex is attached to the cell membrane via membrane-anchoring proteins called ERM proteins that plays a central role in cell shape control.[1][6] The protein constituents of the cortex undergo rapid turnover, making the cortex both mechanically rigid and highly plastic, two properties essential to its function. In most cases, the cortex is in the range of 100 to 1000 nanometers thick.

In some animal cells, the protein spectrin may be present in the cortex. Spectrin helps to create a network by cross-linked actin filaments.[3] The proportions of spectrin and actin vary with cell type.[7] Spectrin proteins and actin microfilaments are attached to transmembrane proteins by attachment proteins between them and the transmembrane proteins. The cell cortex is attached to the inner cytosolic face of the plasma membrane in cells where the spectrin proteins and actin microfilaments form a mesh-like structure that is continuously remodeled by polymerization, depolymerization and branching.

Many proteins are involved in the cortex regulation and dynamics, including formins, with roles in actin polymerization, Arp2/3 complexes that give rise to actin branching and capping proteins. Due to the branching process and the density of the actin cortex, the cortical cytoskeleton can comprise a highly complex meshwork such as a fractal structure.[8] Specialized cells are usually characterized by a very specific cortical actin cytoskeleton. For example, in red blood cells, the cell cortex consists of a two-dimensional cross-linked elastic network with pentagonal or hexagonal symmetry, tethered to the plasma membrane and formed primarily by spectrin, actin and ankyrin.[9] In neuronal axons, the actin or spectric cytoskeleton forms an array of periodic rings [10] and in the sperm flagellum it forms a helical structure.[11]

In plant cells, the cell cortex is reinforced by cortical microtubules underlying the plasma membrane. The direction of these cortical microtubules determines which way the cell elongates when it grows.

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  7. ^ Machnicka B, Grochowalska R, Bogusławska DM, Sikorski AF, Lecomte MC (January 2012). "Spectrin-based skeleton as an actor in cell signaling". Cellular and Molecular Life Sciences. 69 (2): 191–201. doi:10.1007/s00018-011-0804-5. PMC 3249148. PMID 21877118.
  8. ^ Sadegh S, Higgins JL, Mannion PC, Tamkun MM, Krapf D (2017). "Plasma Membrane is Compartmentalized by a Self-Similar Cortical Actin Meshwork". Physical Review X. 7 (1): 011031. arXiv:1702.03997. Bibcode:2017PhRvX...7a1031S. doi:10.1103/PhysRevX.7.011031. PMC 5500227. PMID 28690919.
  9. ^ Gov NS (January 2007). "Active elastic network: cytoskeleton of the red blood cell". Physical Review E. 75 (1 Pt 1): 011921. Bibcode:2007PhRvE..75a1921G. doi:10.1103/PhysRevE.75.011921. PMID 17358198.
  10. ^ Xu K, Zhong G, Zhuang X (January 2013). "Actin, spectrin, and associated proteins form a periodic cytoskeletal structure in axons". Science. 339 (6118): 452–6. Bibcode:2013Sci...339..452X. doi:10.1126/science.1232251. PMC 3815867. PMID 23239625.
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