Review Article | Published:

Focal adhesion kinase: in command and control of cell motility

Nature Reviews Molecular Cell Biology volume 6, pages 5668 (2005) | Download Citation



A central question in cell biology is how membrane-spanning receptors transmit extracellular signals inside cells to modulate cell adhesion and motility. Focal adhesion kinase (FAK) is a crucial signalling component that is activated by numerous stimuli and functions as a biosensor or integrator to control cell motility. Through multifaceted and diverse molecular connections, FAK can influence the cytoskeleton, structures of cell adhesion sites and membrane protrusions to regulate cell movement.

Key points

  • In 1992, focal adhesion kinase (FAK) was identified as a substrate for viral Src and as a highly tyrosine-phosphorylated protein that localized to cell adhesion sites known as focal contacts. Since then, FAK has been shown to have a key role in both normal and tumour cell migration downstream of growth factor- and integrin- receptors. It is the formation of a FAK–Src signalling complex that is an initial and important event required for maximal FAK activation and cell migration.

  • FAK can be activated through intermolecular and intramolecular mechanisms, and tyrosine-phosphorylated FAK promotes interactions with various Src-homology (SH)2- and SH3-containing proteins. These proteins allow FAK activation to be connected to several signalling pathways such as the extracellular signal-regulated kinase 2 (ERK2)/mitogen-activated protein kinase (MAPK) cascade and small GTPases such as Rac and Rho. Phosphorylation of the C-terminal domain of FAK might control its localization to focal contacts by altering the binding of paxillin.

  • FAK functions as a signalling-protein scaffold for the assembly and subsequent maturation of focal contacts. FAK–Src kinase activity contributes to these events by promoting signalling that leads to the phosphorylation of phosphatidylinositol lipids. FAK–Src also functions to promote the disassembly of focal contacts, in part by activating intracellular proteases such as calpain and extracellular matrix metalloproteinases. New findings also link FAK–Src signalling to the regulation of cadherin-mediated cell–cell contacts.

  • In cell protrusions of migrating cells, coordinated changes in actin and microtubule structures are regulated by FAK signalling to Rho-family GTPases. FAK binds to and can phosphorylate GTPase-activating proteins (GAPs) and guanine nucleotide-exchange factors (GEFs) for Rho, and neuronal Wiskott–Aldrich syndrome protein (N-WASP), and can exert control over actin crosslinking by phosphorylating α-actinin.

  • The receptor-proximal position of FAK facilitates its role as an integrator of biochemical signals and mechanical forces that are experienced by moving cells. It is in this unique signalling position that FAK can regulate cytoskeletal or cell adhesion site dynamics and thereby control cell motility.

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S. Mitra is supported by a fellowship from the California Tobacco-Related Disease Research Program and D. Schlaepfer is supported by grants from the National Cancer Institute. This is manuscript 16827-IMM from The Scripps Research Institute.

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  1. The Scripps Research Institute, Department of Immunology, IMM21 10550 North Torrey Pines Road, La Jolla, California 92037, USA.

    • Satyajit K. Mitra
    • , Daniel A. Hanson
    •  & David D. Schlaepfer


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Correspondence to David D. Schlaepfer.



A large family of heterodimeric transmembrane proteins that function as receptors for cell-adhesion molecules.


(ECM). The complex, multi-molecular material that surrounds cells. The ECM comprises a scaffold on which tissues are organized, it provides cellular microenvironments and it regulates various cellular functions.


A subfamily of small (21 kDa) GTP-binding proteins that are related to Ras and that regulate the cytoskeleton. The nucleotide-bound state is regulated by GTPase-activating proteins, which catalyse hydrolysis of the bound GTP, and guanine nucleotide-exchange factors, which catalyse GDP–GTP exchange.


Also termed 'actin-microfilament bundles', these are bundles of parallel filaments that contain F-actin and other contractile molecules, and often stretch between cell attachments as if under stress.


Broad, flat protrusions at the leading edge of a moving cell that are enriched with a branched network of actin filaments.


An established tissue-culture strain of human epidermoid carcinoma cells, containing 70–80 chromosomes per cell. These cells were originally derived from tissue taken from a patient named Henrietta Lacks in 1951.


Proteins that augment cellular responses by recruiting other proteins to a complex. They usually contain several protein–protein interaction domains.


A seven-helix membrane-spanning cell-surface receptor that signals through heterotrimeric GTP-binding and GTP-hydrolysing G-proteins to stimulate or inhibit the activity of a downstream enzyme.


A protein sequence of 50 amino acids that recognizes and binds sequences that are rich in proline.


(GAP). A protein that stimulates the intrinsic ability of a GTPase to hydrolyse GTP to GDP. Therefore, GAPs negatively regulate GTPases by converting them from active (GTP-bound) to inactive (GDP-bound).


The transfer of a phosphate group by a protein kinase either to a residue in the same kinase molecule (cis) or to a residue in a different kinase molecule but of the same type (trans).


A protein motif that recognizes and binds tyrosine-phosphorylated sequences, and thereby has a key role in relaying cascades of signal transduction.


Kinases that belong to the Src family of tyrosine kinases, the largest of the non-receptor-tyrosine-kinase families.


A region in the spleen in which white blood cell precursors such as B-cells, granulocytes, macrophages and plasma-cells reside or transit through during primary or secondary immune responses.


A conserved structural motif in kinase domains, which needs to be phosphorylated for full activation of the kinase.


A protein that facilitates the exchange of GDP for GTP in the nucleotide-binding pocket of a GTP-binding protein.


A process that is formed by the movement of lamellipodia that are in the dynamic process of folding back onto the cell body from which they previously extended.


A short sequence found within proteins that has the consensus sequence LDXLLXXL and functions as a protein-binding interface.


Proteolytic enzymes that degrade the extracellular matrix and have important roles in tissue remodelling and tumour metastasis.


The thin margin of a lamellipodium that spans the area of the cell from the plasma membrane to a depth of about 1 μm into the lamellipodium.


A complex that consists of two actin-related proteins ARP2 and ARP3, along with five smaller proteins. When activated, the ARP2/3 complex binds to the side of an existing actin filament and nucleates the assembly of a new actin filament. The resulting branch structure is Y-shaped.


An anionic glycosphingolipid that carries, in addition to other sugar residues, one or more sialic acid residues.


Lateral aggregates of cholesterol and sphingomyelin that are thought to occur in the plasma membrane.


A cell–cell adhesion complex that contains classical cadherins and catenins that are attached to cytoplasmic actin filaments.


A circumferential ring at the apex of epithelial cells that seals adjacent cells to one another. Tight junctions regulate solute and ion flux between adjacent epithelial cells.


A defective protein that retains interaction capabilities and so competes with normal proteins, thereby impairing protein function.


A planar force exerted by the friction of a flowing substance — for example, forces experienced by endothelial cells as blood flows through capillaries.


The inner trophoblastic layer of cells that give rise to the syncytiotrophoblast facing the maternal circulation and constitute a layer through which all substances must pass from the mother to the fetus.

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