Name: integrins trigger focal adhesion signaling
Uploaded: 2023-04-30T11:54:28.000Z
Duration: 1 min 17 s
Channel: JoVE

Clusters of integrins on the cell membrane can temporarily bridge extracellular matrix ligands to the cytoskeleton to form focal adhesion complexes.
Focal adhesions can grow and shrink, allowing the cell to crawl during migration.
While the adhesion originates at the cell membrane, signals are transmitted by protein kinases and G-proteins in a cascade throughout the cell.
For example, thrombin, an extracellular signaling molecule in platelets, activates G-protein coupled receptor, cAR1/cAR3, which in turn activates Rap1&#160; GTPase.
Active Rap1 interacts with a Rap1-GTP-interacting adaptor molecule or RIAM that recruits inactive talin to the cell membrane.
Inactive talin&#39;s N-terminal head and C-terminal tail domains are folded together. Binding a phosphoinositide in the cell membrane disrupts the head-tail interaction, helping talin unfold.
Together with kindlin, talin activates integrin and binds other adaptor proteins such as vinculin, which link integrin to the actin filaments.

intracellular signaling affects focal adhesions

Intracellular Signaling Affects Focal Adhesions

Integrins act both as extracellular input receivers and as intracellular processing activators. As their name suggests, integrins are entirely integrated into the membrane structure. Their hydrophobic membrane-spanning regions interact with the phospholipid bilayer&#39;s hydrophobic region. These membrane receptors provide extracellular attachment sites for effectors like hormones and growth factors. They activate intracellular response cascades when their effectors are bound and active.
Some integrin-mediated stimulation pathways induce cell proliferation and promote cell survival. The adhesions originate at the cell membrane, but the signals are transmitted throughout the cell by G-proteins and protein kinases in a cascade. For example, thrombin binding to G-protein coupled receptors triggers intracellular signaling to activate integrins in platelets. Activated integrins bind to RGD-peptide sequences on blood proteins, such as fibrinogen. As the fibrinogens start forming bridges, the focal adhesions cluster together, and the platelets aggregate.
Integrins can also directly bind signaling proteins and relay the signals into the cell. In the Ras/MAP kinase pathway, focal adhesion kinase (FAK), a cytoplasmic protein kinase, is the best-studied modes of integrin signaling.&#160; Studies suggest that focal adhesions contain many tyrosine phosphorylation sites and thus contain tyrosine-phosphorylated proteins such as FAK. Integrins cluster at cell-matrix junctions, and the &#946; subunit recruits FAK through adaptor proteins such as paxillin or talin bound to the &#945; subunit. The FAK proteins cluster at the site and phosphorylate a specific tyrosine site on each other. This creates a phospho-tyrosine docking site for Src proteins belonging to the cytoplasmic tyrosine kinases family. The FAK additionally phosphorylates other tyrosine sites, thus establishing docking sites for various proteins involved in intracellular signaling.

Integrins act both as extracellular input receivers and as intracellular processing activators. As their name suggests, integrins are entirely integrated ...

intracellular-signaling-affects-focal-adhesions

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JoVE Core

Cell Biology

Unit 1

Cell-Matrix Interactions

KEY TERMS AND CONCEPTS

integrins trigger focal adhesion signaling

Integrins trigger focal adhesion signaling at the cell membrane. These membrane receptors sit in the phospholipid bilayer with hydrophobic regions that match the membrane interior. They provide attachment sites for outside signals such as hormones and growth factors. When these effectors bind and become active, integrins can start response pathways inside the cell.

Some integrin-driven pathways support cell growth and help cells survive. The signal begins at the membrane, but G-proteins and protein kinases carry it through the cell in a cascade. In platelets, thrombin binds to G-protein-coupled receptors and activates integrins. The activated integrins then bind RGD peptide sequences on blood proteins such as fibrinogen. As fibrinogen bridges form, focal adhesions cluster and the platelets aggregate.

Integrins can also pass signals directly into the cell by binding signaling proteins. In the Ras/MAP kinase pathway, focal adhesion kinase, or FAK, is the best-studied example of integrin signaling. Focal adhesions contain many tyrosine phosphorylation sites, so they include tyrosine-phosphorylated proteins such as FAK. Integrins cluster at cell-matrix junctions, and the beta subunit recruits FAK through adaptor proteins such as paxillin or talin bound to the alpha subunit.

FAK proteins cluster at the site and phosphorylate a specific tyrosine on each other. This creates a phospho-tyrosine docking site for Src proteins, which are cytoplasmic tyrosine kinases. FAK also phosphorylates other tyrosine sites. These new docking sites recruit more proteins that help carry out intracellular signaling.

Integrins Trigger Focal Adhesion Signaling

integrins-trigger-focal-adhesion-signaling

overview of cell-matrix interactions

ECM Proteins and Cell Signaling

The extracellular matrix, or ECM, is the material that helps hold cells together in a tissue. It also lets cells in that tissue communicate with one another. The ECM contains proteins such as fibronectin, collagen, and laminin. Collagen is the most abundant protein in this space. Collagen fibers are woven together with proteoglycans, which are protein molecules with carbohydrates attached. This mix gives the ECM its structure. It also supports cell migration and provides a scaffold for cell...

integrins

Integrins in Cell Adhesion

Integrins help animal and protozoan cells attach to the extracellular matrix, or ECM. These cells do not have cell walls, so the ECM helps maintain shape and provide structural stability. The ECM is a sticky network of carbohydrates and proteins found between adjacent cells. Some ECM proteins form a basement membrane, and other ECM parts adhere to it. Proteoglycans make up much of the ECM, while fibrous proteins such as collagen give it strength. Fibronectin connects proteoglycans and collagen...

activation of integrins

How Integrins Link Cells to Their Environment

Integrins help cells connect with their environment and send signals across the cell membrane. They can carry information from outside the cell to the inside, or from inside the cell to the outside. These two paths are called outside-in signaling and inside-out signaling. In outside-in signaling, molecules in the extracellular space bind to exposed ligand-binding sites on integrins. A ligand is a molecule that binds to a protein. This binding makes the inactive integrin change shape and become...

Integrins trigger focal adhesion signaling at the cell membrane. These membrane receptors sit in the phospholipid bilayer with hydrophobic regions that match the membrane interior. They provide attachment sites for outside signals such as hormones and growth factors. When these effectors bind and become active, integrins can start response pathways inside the cell. Some integrin-driven pathways support cell growth and help cells survive. The signal begins at the membrane, but G-proteins and...

anchoring junctions

Cell Adhesion in Anchoring Junctions

Anchoring junctions are multiprotein complexes that help cells connect to other cells and to the extracellular matrix. They sit on the lateral and basal surfaces of cells. These junctions create strong, flexible links that help maintain tissue stability and integrity. Focal adhesions often form when cells interact with the extracellular matrix, or ECM, substrata. These contacts can start signal transduction through kinase cascades and other pathways. Together, these junctions help cells stay...

cell-matrix's response to mechanical forces

cell-matrix-s-response-to-mechanical-forces

Focal Adhesions and Cell Mechanics

Focal adhesions help animal cells connect to the extracellular matrix and sense mechanical forces. The extracellular matrix, or ECM, sits outside cells and helps tissues withstand stress. It also sends signals from outside the cell to the inside. The ECM is large and its makeup changes from one tissue to another. In loose connective tissue, reticular fibers and ground substance form the ECM. In bone tissue, collagen and bone minerals make up the ECM. Anchoring junctions hold a cell to the...

key terms and concepts

Learn how integrins activate focal adhesion signaling, connect to fibrinogen in platelets, and recruit FAK, Src, and other proteins inside the cell.

Integrins Trigger Focal Adhesion Signaling | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

Integrins Trigger Focal Adhesion Signaling

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