Focal adhesion

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Focal Adhesion

Focal adhesions are complex multi-protein structures that form mechanical links between intracellular actin filaments and the extracellular matrix (ECM). They play a crucial role in cellular processes such as adhesion, migration, proliferation, and signal transduction.

Structure

Focal adhesions are composed of clusters of proteins that include integrins, which are transmembrane receptors that mediate the attachment between a cell and its surroundings. The intracellular side of integrins is linked to the actin cytoskeleton through a variety of adaptor proteins such as talin, vinculin, and paxillin.

Integrins

Integrins are heterodimeric proteins consisting of α and β subunits. They are responsible for sensing the ECM and transmitting signals into the cell. Integrins can bind to ECM proteins such as fibronectin, collagen, and laminin.

Adaptor Proteins

Adaptor proteins such as talin and vinculin connect integrins to the actin cytoskeleton. Talin binds to the cytoplasmic tail of integrins and recruits vinculin, which further stabilizes the linkage to actin filaments.

Signaling Molecules

Focal adhesions are also sites of signal transduction. They contain kinases such as focal adhesion kinase (FAK) and Src, which are involved in signaling pathways that regulate cell survival, proliferation, and motility.

Function

Focal adhesions serve several key functions in cells:

• Mechanical Anchorage: They provide a stable anchor for cells to attach to the ECM, allowing cells to maintain their shape and resist mechanical stress.
• Signal Transduction: Focal adhesions act as signaling hubs that relay information from the ECM to the cell interior, influencing cell behavior and fate.
• Cell Migration: During cell migration, focal adhesions form at the leading edge of the cell and disassemble at the trailing edge, allowing the cell to move forward.

Dynamics

Focal adhesions are dynamic structures that can rapidly assemble and disassemble in response to cellular signals and environmental cues. This dynamic nature is essential for processes such as wound healing, immune response, and cancer metastasis.

Clinical Relevance

Abnormal focal adhesion dynamics are implicated in various diseases, including cancer, where altered cell adhesion and migration contribute to tumor progression and metastasis. Understanding focal adhesion biology is crucial for developing therapeutic strategies targeting these processes.

Also see

• Integrin
• Extracellular matrix
• Cell migration
• Signal transduction
• Actin cytoskeleton

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