Name: extracellular matrix support proteins
Uploaded: 2023-04-30T11:53:25.000Z
Duration: 1 min 21 s
Channel: JoVE

Matrix proteoglycans are composed of several glycosaminoglycans chains covalently attached to a core protein. They are commonly found in the extracellular matrix or ECM and at the cell membrane.
In contrast, in glycoproteins, a protein core is covalently attached to oligosaccharide chains. They come in different forms and are usually found on the cell membrane, in the ECM, and in blood.
Cells communicate with other cells by secreting signaling proteins that travel through the dense ECM network to reach their designated cells.
The proteoglycans with multiple binding sites act as local reservoirs for vascular endothelial growth factors that are responsible for cell proliferation.
In this way, proteoglycans limit the diffusion of the growth factor, localizing their effect on nearby cells.
Proteoglycans also protect several signaling proteins from degradation by proteases.
Similarly, glycoproteins, such as integrins, serve as cell surface receptors for another glycoprotein called fibronectin. These two glycoproteins together play major roles in connecting cells with the ECM.

matrix proteoglycans and glycoproteins

Matrix Proteoglycans and Glycoproteins

Proteoglycans are extensively glycosylated proteins, commonly found in the extracellular matrix, interwoven with collagen fibers. Hyaline cartilage, the most common type of cartilage in the body, consists of short and dispersed collagen fibers associated with large amounts of proteoglycans. These proteoglycans have long negative charges that attract cations, which in turn attract water molecules. This influx of ions and water molecules swells up the proteoglycan like a water-soaked gel that can withstand the compression forces.
The two common examples of matrix glycoproteins are integrin, laminin, and fibronectin. Integral proteins, or integrins, as their name suggests, integrate completely into the membrane structure with their hydrophobic membrane-spanning regions interacting with the phospholipid bilayer&#39;s hydrophobic region. Integral proteins may serve as enzymes, as structural attachments for the cytoskeleton&#39;s fibers, or as part of the cell&#8217;s recognition sites. Collagen and proteoglycan are attached to fibronectin proteins, which are further attached to integrin proteins. For example, the bacterium Streptococcus pyogenes, which is known to cause strep throat and various other infections, attach to fibronectin present in the extracellular matrix of the cells lining the oropharynx. Laminins are important for cell migration, growth and differentiation. In association with type IV collagens, the laminins form an interconnected network that provides strength and flexibility to the basal lamina.
This text is adapted from:
&#160;<a href="https://openstax.org/books/anatomy-and-physiology-2e/pages/4-3-connective-tissue-supports-and-protects">Openstax, Anatomy and physiology 2e, Section 4.3: Connective tissue supports and protects.</a>
<a href="https://openstax.org/books/biology-2e/pages/5-1-components-and-structure">Openstax, Biology 2e, Section 5.1: Components and Structure.</a>
<a href="https://openstax.org/books/microbiology/pages/3-4-unique-characteristics-of-eukaryotic-cells">Openstax, Microbiology, Section 3.4: Unique characteristics of Eukaryotic cells.</a>

Proteoglycans are extensively glycosylated proteins, commonly found in the extracellular matrix, interwoven with collagen fibers. Hyaline cartilage, the ...

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JoVE Core

Cell Biology

Unit 1

Extracellular Matrix in Animals

KEY TERMS AND CONCEPTS

extracellular matrix support proteins

Proteoglycans and matrix glycoproteins help build the extracellular matrix. The extracellular matrix is the material outside cells that gives tissues support and structure. Proteoglycans are heavily glycosylated proteins, and they are commonly found woven through collagen fibers.

Hyaline cartilage shows how proteoglycans work. This is the most common type of cartilage in the body. It contains short, scattered collagen fibers with large amounts of proteoglycans. The proteoglycans carry long negative charges. These charges attract cations, and the cations attract water molecules. As water moves in, the proteoglycan swells like a water-soaked gel. This helps the tissue resist compression forces.

Matrix glycoproteins also help connect and organize cells in the extracellular matrix. Common examples include integrin, laminin, and fibronectin. Integrins are integral proteins, which means they span the membrane and fit into its structure. Their hydrophobic membrane-spanning regions interact with the hydrophobic part of the phospholipid bilayer. Integral proteins may act as enzymes, as attachments for cytoskeletal fibers, or as part of cell recognition sites.

Fibronectin can bind collagen and proteoglycans, and these are linked to integrin proteins. This connection helps anchor structures in the matrix. It also gives bacteria a place to attach. Streptococcus pyogenes, which can cause strep throat and other infections, attaches to fibronectin in the extracellular matrix of the cells lining the oropharynx. Laminins are also important. They help with cell migration, growth, and differentiation. Together with type IV collagens, laminins form an interconnected network that gives the basal lamina strength and flexibility.

Extracellular Matrix Support Proteins

the extracellular matrix

How the Extracellular Matrix Shapes Tissues

The extracellular matrix, or ECM, helps animal tissues stay organized and keeps cells in the right place. It is made of structural molecules that support tissue shape and give certain tissues their special properties. The ECM usually contains a gel-like ground substance, fibrous parts, and many molecules with different jobs. One major group is glycosaminoglycans, or GAGs, which are polysaccharides. GAGs fill much of the space outside cells and can take up a large volume compared with their...

glycosaminoglycans

GAGs in Tissue Support and Lubrication

Glycosaminoglycans, or GAGs, are long, linear polymers that help build and protect animal tissues. They are also called mucopolysaccharides. Their repeating units are made of an amino sugar, such as N-acetylglucosamine or N-acetylgalactosamine, plus a uronic acid, usually glucuronic acid or iduronic acid. GAGs are found in the extracellular matrix of vertebrates, invertebrates, and bacteria. Their polar nature lets them attract water. This makes them useful as lubricants and as shock absorbers...

collagens are the major structural proteins of ecm

collagens-are-the-major-structural-proteins-of-ecm

Collagen Fibers Give Tissues Strength

Collagen fibers give connective tissues strength and help them resist stretching. They are one of three main fiber types secreted by fibroblasts, along with elastic fibers and reticular fibers. Collagen fibers are made from fibrous protein subunits linked into long, straight fibers. These fibers are flexible, but they also have great tensile strength. Tensile strength is the ability to resist pulling forces. Collagen fibers help ligaments and tendons stay resilient and strong. They also hold...

fibril-associated collagen

FACIT Collagens in the Extracellular Matrix

FACIT collagens are fibril-associated collagens found in the extracellular matrix. FACIT stands for fibril-associated collagens with interrupted triple helices. These collagens help connect collagen fibrils to each other and to other extracellular matrix proteins. Type II collagen fibrils in cartilage provide a clear example. They have covalently bound type IX fibril-associated collagens at regular intervals. Other FACIT collagens include types XII, XIV, XVI, XIX, XX, XXI, and XXII. These...

elastin is responsible for tissue elasticity

elastin-is-responsible-for-tissue-elasticity

Elastic Tissues in Skin, Vessels, and Ears

Elastic tissues contain elastin, a protein mixed with smaller amounts of other proteins and glycoproteins. Elastin helps tissue return to its original shape after it is stretched or compressed. This property is important in body parts that must bend, stretch, and recoil. Elastic fibers are found in elastic tissues in the skin and in the elastic ligaments of the vertebral column. Ligaments and tendons are both made of dense regular connective tissue, but ligaments do not always have all of...

fibronectins connect cells with ecm

Fibronectin and Cell Attachment in ECM

Fibronectin is an adhesive glycoprotein in the extracellular matrix of embryogenic and adult tissue. It helps regulate cell motility and attachment. In many tissues, fibronectin gives cells a place to bind and move along. A fibronectin molecule is made of two identical polypeptide chains. These chains are joined at the C-terminal by a pair of disulfide bonds. Fibronectin also binds proteoglycans and collagen. It then links to integrin proteins, which interact with transmembrane proteins in the...

Proteoglycans and matrix glycoproteins help build the extracellular matrix. The extracellular matrix is the material outside cells that gives tissues support and structure. Proteoglycans are heavily glycosylated proteins, and they are commonly found woven through collagen fibers. Hyaline cartilage shows how proteoglycans work. This is the most common type of cartilage in the body. It contains short, scattered collagen fibers with large amounts of proteoglycans. The proteoglycans carry long...

role of matrix metalloproteases in degradation of ecm

role-of-matrix-metalloproteases-in-degradation-of-ecm

How MMPs Remodel the Extracellular Matrix

Matrix metalloproteases (MMPs) are enzymes that break down proteins and glycoproteins in the extracellular matrix, or ECM. The ECM is the dense network around cells. By cutting ECM molecules, MMPs help cells move and grow through tissue. MMPs are important during embryonic development and morphogenesis, the process that shapes body form. A classic example comes from a tadpole’s tail during metamorphosis. The first MMP activity discovered was a collagenase, an enzyme that cuts collagen. This...

basal lamina are the specialized form of ecm

basal-lamina-are-the-specialized-form-of-ecm

Basal Lamina Structure and Cell Attachment

The basal lamina is a thin extracellular layer that sits beneath cells and separates them from other tissues. It acts as a support layer for epithelium and helps anchor it to the tissue below. Its structure includes three layers: lamina lucida, lamina densa, and lamina reticularis. The basal lamina is made of glycoproteins and collagen. Key proteins in this framework include laminins, perlecan, entactin, and type IV collagen. Cell membrane proteins such as integrins and dystroglycan bind to...

laminins are the adhesive proteins of basal lamina

laminins-are-the-adhesive-proteins-of-basal-lamina

Laminin Structure and Basal Lamina Support

Laminins are large extracellular matrix proteins that help build the basal lamina. Each laminin molecule has three chains: alpha, beta, and gamma. These chains are encoded by five alpha genes, four beta genes, and three gamma genes. In humans, the alpha chains are LAMA1, LAMA2, LAMA3, LAMA4, and LAMA5. The beta chains are LAMB1, LAMB2, LAMB3, and LAMB4. The gamma chains are LAMC1, LAMC2, and LAMC3. Laminin types are named based on which three chains they contain. Laminins join with one...

type iv collagen of basal lamina

Type IV Collagen in Basement Membranes

Type IV collagen is a network-forming collagen found in basement membranes. It acts as a barrier between epithelial and endothelial cells. It also helps form the backbone of the basement membrane with laminin, entactin, proteoglycans, and fibronectin. Beyond support, type IV collagen also helps with signaling functions linked to normal body processes and disease. A type IV collagen molecule contains six alpha chains. These chains can form at least three heterotrimeric triple-helical...

key terms and concepts

Learn how proteoglycans and matrix glycoproteins support cartilage, bind water, connect cells, and help form the basal lamina in the extracellular matrix.

Extracellular Matrix Support Proteins | JoVE K12

cell biology

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Extracellular Matrix Support Proteins

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