Cortactin

Last updated
CTTN
Protein CTTN PDB 1x69.png
Available structures
PDB Ortholog search: PDBe RCSB
Identifiers
Aliases CTTN , EMS1, cortactin
External IDs OMIM: 164765 MGI: 99695 HomoloGene: 3834 GeneCards: CTTN
Orthologs
SpeciesHumanMouse
Entrez
Ensembl
UniProt
RefSeq (mRNA)

NM_001184740
NM_005231
NM_138565

NM_001252572
NM_007803
NM_001357116

RefSeq (protein)

NP_001171669
NP_005222
NP_612632

NP_001239501
NP_031829
NP_001344045

Location (UCSC) Chr 11: 70.4 – 70.44 Mb Chr 7: 143.99 – 144.02 Mb
PubMed search [3] [4]
Wikidata
View/Edit Human View/Edit Mouse

Cortactin (from "cortical actin binding protein") is a monomeric protein located in the cytoplasm of cells that can be activated by external stimuli to promote polymerization and rearrangement of the actin cytoskeleton, especially the actin cortex around the cellular periphery. [5] [6] It is present in all cell types. When activated, it will recruit Arp2/3 complex proteins to existing actin microfilaments, facilitating and stabilizing nucleation sites for actin branching. Cortactin is important in promoting lamellipodia formation, invadopodia formation, cell migration, and endocytosis.

Contents

Gene

In humans, cortactin is encoded by the CTTN gene on chromosome 11. [7]

Structure

Cortactin is a thin, elongated monomer that consists of an amino-terminal acidic (NTA) region; 37-residue-long segments that are highly conserved among cortactin proteins of all species and repeated up to 6.5 times in tandem (“cortactin repeats”); a proline-rich region; and an SH3 domain. This basic structure is highly conserved among all species that express cortactin. [8]

Activation and binding

Cortactin is activated via phosphorylation, by tyrosine kinases or serine/threonine kinases, in response to extracellular signals like growth factors, adhesion sites, or pathogenic invasion of the epithelial layer.

The SH3 domain of certain tyrosine kinases, such as the oncogene Src kinase, binds to cortactin's proline-rich region and phosphorylates it on Tyr421, Tyr466, and Tyr482. Once activated in this way, it can bind to filamentous actin (F-actin) with the fourth of its cortactin repeats. [8] As the concentration of phosphorylated cortactin increases in specific regions within the cell, the monomers each begin to recruit an Arp2/3 complex to F-actin. It binds to Arp2/3 with an aspartic acid-aspartic acid-tryptophan (DDW) sequence in its NTA region, a motif that is often seen in other actin nucleation-promoting factors (NPFs). [9]

Certain serine/threonine kinases, such as ERK, can phosphorylate cortactin on Ser405 and Ser418 in the SH3 domain. [8] Activated like this, it still associates with Arp2/3 and F-actin, but will also allow other actin NPFs, most importantly N-WASp (Neuronal Wiskott-Aldrich syndrome protein), to bind to the complex as well; when phosphorylated by tyrosine kinases, other NPFs are excluded. [10] The ability of these other NPFs to bind the Arp2/3 complex while cortactin is also bound could come from new interactions with cortactin's SH3 domain, which is in a different conformation when phosphorylated by Ser/Thr kinases and thus may be more open to interactions with other NPFs. [10] Having other NPFs bind to the Arp2/3 complex at the same time as cortactin may enhance nucleation site stability. [8]

Location and function in the cell

Inactive cortactin diffuses throughout the cytoplasm, but upon phosphorylation, the protein begins to target certain areas in the cell. Cortactin-assisted Arp2/3-nucleated actin branches are most prominent in the actin cortex, around the periphery of the cell. [11] A phosphorylated cortactin monomer binds to, activates, and stabilizes an Arp2/3 complex on preexisting F-actin, which provides a nucleation site for a new actin branch to form from the “mother” filament. Branches formed from cortactin-assisted nucleation sites are very stable; cortactin has been shown to inhibit debranching. [11] Thus, polymerization and branching of actin is promoted in areas of the cell where cortactin is localized.

Cortactin is very active in lamellipodia, protrusions of the cell membrane formed by actin polymerization and treadmilling that propel the cell along a surface as it migrates towards some target. [12]

Cortactin acts as a link between extracellular signals and lamellipodial “steering.” When a receptor tyrosine kinase on the cell membrane binds to an adhesion site, for example, cortactin will be phosphorylated locally to the area of binding, activate and recruit Arp2/3 to the actin cortex in that region, and thus stimulate cortical actin polymerization and movement of the cell in that direction. Macrophages, highly motile immune cells that engulf cellular debris and pathogens, are propelled by lamellipodia and identify/migrate toward a target via chemotaxis; thus, cortactin must also be activated by receptor kinases that pick up a large variety of chemical signals. [12]

Studies have implicated cortactin in both clathrin-mediated endocytosis [13] and clathrin-independent endocytosis. [14] In both kinds of endocytosis, it has long been known that actin localizes to sites of vesicle invagination and is a vital part of the endocytic pathway, but the actual mechanisms by which actin facilitates endocytosis are still unclear. Recently, however, it has been found that dynamin, the protein responsible for breaking the newly formed vesicular bud off the inside of the plasma membrane, can associate with the SH3 domain of cortactin. Since cortactin recruits the Arp2/3 complexes that lead to actin polymerization, this suggests that it may play an important part in linking vesicle formation to the as yet unknown functions actin has in endocytosis. [15]

Clinical significance

Amplification of the genes encoding cortactin—in humans, EMS1—has been found to occur in certain tumors. Overexpression of cortactin can lead to highly-active lamellipodia in tumor cells, dubbed “invadopodia.” These cells are especially invasive and migratory, making them very dangerous, for they can easily spread cancer across the body into other tissues. [16]

Interactions

Cortactin has been shown to interact with:

See also

Related Research Articles

<span class="mw-page-title-main">Wiskott–Aldrich syndrome protein</span> Mammalian protein found in humans

The Wiskott–Aldrich syndrome protein (WASp) is a 502-amino acid protein expressed in cells of the hematopoietic system that in humans is encoded by the WAS gene. In the inactive state, WASp exists in an autoinhibited conformation with sequences near its C-terminus binding to a region near its N-terminus. Its activation is dependent upon CDC42 and PIP2 acting to disrupt this interaction, causing the WASp protein to 'open'. This exposes a domain near the WASp C-terminus that binds to and activates the Arp2/3 complex. Activated Arp2/3 nucleates new F-actin.

The lamellipodium is a cytoskeletal protein actin projection on the leading edge of the cell. It contains a quasi-two-dimensional actin mesh; the whole structure propels the cell across a substrate. Within the lamellipodia are ribs of actin called microspikes, which, when they spread beyond the lamellipodium frontier, are called filopodia. The lamellipodium is born of actin nucleation in the plasma membrane of the cell and is the primary area of actin incorporation or microfilament formation of the cell.

<span class="mw-page-title-main">Paxillin</span> Protein-coding gene in the species Homo sapiens

Paxillin is a protein that in humans is encoded by the PXN gene. Paxillin is expressed at focal adhesions of non-striated cells and at costameres of striated muscle cells, and it functions to adhere cells to the extracellular matrix. Mutations in PXN as well as abnormal expression of paxillin protein has been implicated in the progression of various cancers.

<span class="mw-page-title-main">Adapter molecule crk</span> Protein-coding gene in the species Homo sapiens

Adapter molecule crk also known as proto-oncogene c-Crk is a protein that in humans is encoded by the CRK gene.

<span class="mw-page-title-main">PTK2</span> Protein-coding gene in humans

PTK2 protein tyrosine kinase 2 (PTK2), also known as focal adhesion kinase (FAK), is a protein that, in humans, is encoded by the PTK2 gene. PTK2 is a focal adhesion-associated protein kinase involved in cellular adhesion and spreading processes. It has been shown that when FAK was blocked, breast cancer cells became less metastatic due to decreased mobility.

<span class="mw-page-title-main">ACTR3</span> Mammalian protein found in Homo sapiens

Actin-related protein 3 is a protein that in humans is encoded by the ACTR3 gene.

<span class="mw-page-title-main">WASF2</span> Mammalian protein found in Homo sapiens

Wiskott–Aldrich syndrome protein family member 2 is a protein that in humans is encoded by the WASF2 gene.

<span class="mw-page-title-main">NCK1</span> Protein-coding gene in the species Homo sapiens

Cytoplasmic protein NCK1 is a protein that in humans is encoded by the NCK1 gene.

<span class="mw-page-title-main">Vasodilator-stimulated phosphoprotein</span> Mammalian protein found in Homo sapiens

Vasodilator-stimulated phosphoprotein is a protein that in humans is encoded by the VASP gene.

<span class="mw-page-title-main">PTPRA</span> Protein-coding gene in the species Homo sapiens

Receptor-type tyrosine-protein phosphatase alpha is an enzyme that in humans is encoded by the PTPRA gene.

<span class="mw-page-title-main">WASF1</span>

Wiskott–Aldrich syndrome protein family member 1, also known as WASP-family verprolin homologous protein 1 (WAVE1), is a protein that in humans is encoded by the WASF1 gene.

<span class="mw-page-title-main">FER (gene)</span> Protein-coding gene in the species Homo sapiens

Proto-oncogene tyrosine-protein kinase FER is an enzyme that in humans is encoded by the FER gene.

<span class="mw-page-title-main">HCLS1</span> Protein-coding gene in the species Homo sapiens

Hematopoietic lineage cell-specific protein is a protein that in humans is encoded by the HCLS1 gene.

<span class="mw-page-title-main">CD2AP</span> Protein

CD2-associated protein is a protein that in humans is encoded by the CD2AP gene.

<span class="mw-page-title-main">Drebrin-like</span> Protein-coding gene in the species Homo sapiens

Drebrin-like protein is a protein that in humans is encoded by the DBNL gene.

<span class="mw-page-title-main">WIPF1</span> Protein-coding gene in the species Homo sapiens

WAS/WASL-interacting protein (WIP) is a protein that in humans is encoded by the WIPF1 gene.

<span class="mw-page-title-main">ARPC2</span> Mammalian protein found in Homo sapiens

Actin-related protein 2/3 complex subunit 2 is a protein that in humans is encoded by the ARPC2 gene.

<span class="mw-page-title-main">PSTPIP1</span> Enzyme found in humans

Proline-serine-threonine phosphatase-interacting protein 1 is an enzyme that in humans is encoded by the PSTPIP1 gene.

A non-receptor tyrosine kinase (nRTK) is a cytosolic enzyme that is responsible for catalysing the transfer of a phosphate group from a nucleoside triphosphate donor, such as ATP, to tyrosine residues in proteins. Non-receptor tyrosine kinases are a subgroup of protein family tyrosine kinases, enzymes that can transfer the phosphate group from ATP to a tyrosine residue of a protein (phosphorylation). These enzymes regulate many cellular functions by switching on or switching off other enzymes in a cell.

Coronin, actin binding protein, 1B also known as CORO1B is a protein which in humans is encoded by the CORO1B gene. Members of the coronin family, such as CORO1B, are WD repeat-containing actin-binding proteins that regulate cell motility.

References

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Further reading