ECM

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Questions and Answers

Which protein is NOT a type of ECM proteins?

Structural proteins:

Specialized proteins

Proteoglycans

Tropocollagen (correct)

Match the protein type to its proteins

Structural proteins = Collagen, Elastin, Fibrillin Specialized proteins = Fibronectin, Laminin Proteoglycans = GAGs x = x

What is needed for the synthesis of Collagen

Fibroblasts

What is the structural unit of collagen?

Tropocollagen Signup and view all the answers

What does collagen mainly consist of?

Proline, Hydroxyproline (sometimes Lysine and Hydroxylysine) Signup and view all the answers

Why does collagen have a very firm structure?

2H E 2F S - High content of glycine, hydroxyproline - Each turn contains only 3 aa —> tight helix - Formation of right handed superhelix, covalent cross links between th adjacent polypeptide chains - Specific arrangement into fibrils, fibers Signup and view all the answers

What is the first step to the synthesis of collagen?

Synthesis of preprocollagen a chains Signup and view all the answers

How does the first step in the intracellular synthesis of collagen end?

Signal peptide directs chain to ER Signup and view all the answers

What happens in the second step in the intracellular synthesis of collagen?

Removal of signal peptide by signal peptidase. Hydroxylation of proline and lysine residues. Glycosylation of hydroxylysyl residues by addition of glucose and galactose Signup and view all the answers

How does the intracellular synthesis of collagen end?

Exocytosis of the procollagen Signup and view all the answers

How does the formation of tropocollagen from procollagen proceed?

Removal of N extension peptide (aminoproteinase) removal of C extension peptide(carboxyproteinase) Signup and view all the answers

How do the interchain cross links form?

By lysyl oxidase (contains Cu2+) Signup and view all the answers

What does a genetic defect in collagen lead to?

Osteogenesis imperfecta syndrome Signup and view all the answers

What is the cause of Osteogenesis imperfecta aka Brittle bone syndrome

Replacement of glycine by amino acid with bulky side chain Signup and view all the answers

Which answer does not correctly state the manifestations of Osteogenesis imperfecta?

Easy bone fracture, loose joints, poor muscle tone, slight spinal curve Signup and view all the answers

What is the cause of Ehlers Danlos syndrome?

Partial deficiency of procollagen. peptidases —> procollagen not fully converted to tropocollagen Signup and view all the answers

What are the manifestations of Ehlers Danlos syndrome?

Short stature, stretchable skin, hypermobile joints Signup and view all the answers

What is the cause of Lathyrism?

Inhibition of lysyl oxidase by ingestion of sweet pea seeds / copper deficiency which is needed for lysyl oxidase Signup and view all the answers

What are the manifestations of Lathyrism?

3D JA: Deformation of spine, dislocation of joints, demineralization of bone, joint hemorrhage, aortic aneurysm Signup and view all the answers

Elastin is a … like protein

rubber Signup and view all the answers

Where is collagen found in the body?

Skin, bone, cartilage, tendons, ligaments, blood vessels, cornea Signup and view all the answers

Where is elastin found in the body?

Ligaments, lungs, wall of blood vessels Signup and view all the answers

What is the main unit of elastin?

Tropoelastin Signup and view all the answers

Why does elastin have elastic properties?

3 allysine residues interact with 1 unoxidized lysine to form desmosine. Signup and view all the answers

What is the shape of elastin?

Fibrous when extended and globular when relaxed Signup and view all the answers

What is the importance of a-1 anti-trypsin deficiency?

Protects tissues from elastase enzymes from inflammatory cells (neutrophils) Signup and view all the answers

Why do proteinases like trypsin and elastase get secreted?

When the body reacts to acute inflammation (bacterial infection), the inflammatory cells secrete proteinases. Signup and view all the answers

What happens in the absence of a-1 anti-trypsin?

Neutrophil elastase breaks down elastin, damages lung elasticity, causing respiratory complications. Signup and view all the answers

What is fibronectin?

Major protein of the ECM Signup and view all the answers

Where is fibronectin found?

Connective tissue, plasma Signup and view all the answers

What is fibronectin's structure?

2 subunits (identical) connected by a 2 disulfide bond, also has several binding sites. Signup and view all the answers

What does fibronectin bind with?

Heparin, collagen, cell surface receptors (integrin) Signup and view all the answers

What is fibronectin's importance?

It has adhesive characteristics which allows it to adhere with transmembrane receptors like integrin. Signup and view all the answers

What is fibronectin glomerulopathy?

Mutation of the gene coding fibronectin. Signup and view all the answers

What are the effects of fibronectin glomerulopathy?

Abnormal fibronectin in glomeruli of kidneys, leading to abnormal glomerular structures/functions. Signup and view all the answers

What are the manifestations of fibronectin glomerulopathy?

Hematuria, proteinuria, hypertension, renal tubular acidosis, renal failure. Signup and view all the answers

What is fibrillin?

Glycoprotein secreted into ECM by fibroblasts. Signup and view all the answers

Where is fibrillin found?

Suspensory ligaments of lens, aorta. Signup and view all the answers

What is the importance of fibrillin?

Forms scaffold for deposition of elastin. Signup and view all the answers

What is the cause of Marfan’s syndrome?

Mutation of gene encoding for fibrillin. Signup and view all the answers

What are the manifestations of Marfan’s syndrome?

Dislocation of lens, dilatation of aorta, hyperextensibility of joints. Signup and view all the answers

What are cartilage proteins and how are they classified?

Cartilage is avascular CT and classified into collagen and non-collagenous proteins. Signup and view all the answers

What is the main collagen protein?

Collagen type II. Signup and view all the answers

What is collagen type II?

It’s 98% of total collagen in cartilage and contains more hydroxylysine and glycosylation. Signup and view all the answers

What is the most important non-collagenous protein in cartilage?

Proteoglycans (aggrecans), contains KCH (GAGs). Signup and view all the answers

What do the GAGs in cartilage look like?

The 3 are attached to a core protein and have a bottle brush appearance. Signup and view all the answers

Who is the binder in cartilage proteins?

Chondronectin binds type II collagen. Signup and view all the answers

What are bone proteins and how are they classified?

Mineralized CT and classified into collagen and non-collagenous proteins. Signup and view all the answers

What is the most important collagen protein in bone proteins?

Collagen type I (90% of total collagen in bone). Signup and view all the answers

What is the major non-collagenous protein in bone proteins?

Osteocalcin. Signup and view all the answers

Who is the binder in bone proteins?

Osteonectin binds collagen. Signup and view all the answers

What is osteoporosis?

Progressive reduction of bone mass/density. Signup and view all the answers

What are risk factors of osteoporosis?

Aging, Female, Family history, Sedentary life, Intake of caffeine and soda, Low intake of Ca/Mg/Vitamin D, Smoking, Drugs like corticosteroids. Signup and view all the answers

Which protein is NOT a Glycoprotein?

Elastin Signup and view all the answers

Match the protein with its common sites

Collagen = Skin, bone, cartilage, tendons, liver, lungs, vessels, cornea Elastin = Ligaments, lung and blood vessels Fibrillin = Suspensory ligaments of lens, aorta Fibronectin = ECM and Plasma Signup and view all the answers

Match the protein with its structure

Collagen = Tropocollagen stabilized by hydrogen bond and covalent cross links Elastin = Tropoelastin stabilized by desmosine cross links Fibrillin = Cysteine rich motifs stabilized by disulfide bonds Fibronectin = 2 identical polypeptide chains connected by disulfide bonds Signup and view all the answers

Match the protein with its function

Collagen = Supportive Elastin = Elasticity Fibronectin = Adhesion Fibrillin = Scaffold for deposition of elastin and tensile strength in nonelastic tissues Signup and view all the answers

Match the protein with its disorders

Collagen = Osteogenesis imperfecta, Ehlers Danlos, Lathyrism, Scurvy, Tissue fibrosis Elastin = a-1 anti-trypsin deficiency Fibrillin = Marfan Syndrome Fibronectin = Fibronectin glomerulopathy Signup and view all the answers

Study Notes

Collagen & Elastin

Collagen is found in various tissues, including skin, bone, cartilage, tendons, ligaments, blood vessels, and cornea.
Elastin is found in ligaments, lungs, and the walls of blood vessels.
Tropoelastin is the main unit of elastin.
Elastin's elastic properties stem from the formation of desmosine, a molecule created from the interaction of three allysine residues and one unoxidized lysine.
Elastin exhibits fibrous shape when extended and a globular shape when relaxed.

α-1 Antitrypsin Deficiency

α-1 antitrypsin is a protein that protects tissues from elastase enzymes released by inflammatory cells like neutrophils.
During acute inflammation, such as bacterial infection, the body releases proteinases like trypsin and elastase.
In the absence of α-1 antitrypsin, neutrophil elastase breaks down elastin, damaging lung elasticity and leading to respiratory complications like emphysema, COPD, and cirrhosis of the liver.

Fibronectin

Fibronectin is a major protein of the extracellular matrix (ECM).
It's found in connective tissue and plasma.
Fibronectin consists of two identical subunits connected by two disulfide bonds and has several binding sites.
It binds to heparin, collagen, and cell surface receptors like integrin.
Fibronectin's adhesive characteristics allow it to bind to transmembrane receptors like integrin, contributing to cell communication between the extracellular and intracellular environments.
Fibronectin glomerulopathy is a genetic disorder caused by a mutation in the fibronectin gene, leading to abnormal fibronectin production in kidney glomeruli and impaired glomerular function.
Fibronectin glomerulopathy can manifest as hematuria, proteinuria, hypertension, renal tubular acidosis, and renal failure.

Fibrillin

Fibrillin is a glycoprotein secreted into the ECM by fibroblasts.
It is found in the suspensory ligaments of the lens and the aorta.
Fibrillin forms the scaffold for elastin deposition.
Marfan syndrome is caused by a mutation in the gene encoding fibrillin, leading to various complications.
Marfan syndrome can lead to lens dislocation, aortic dilation, and joint hyperextensibility.

Cartilage Proteins

Cartilage is avascular connective tissue containing collagen and non-collagenous proteins.
Collagen type II is the main collagen protein in cartilage, accounting for 98% of the total collagen content.
Proteoglycans, particularly aggrecans containing glycosaminoglycans (GAGs), are the most important non-collagenous proteins in cartilage.
GAGs in cartilage have a bottle brush appearance, with three GAGs attached to a core protein.
Chondronectin, a binder protein, binds to type II collagen in cartilage.

Bone Proteins

Bone is mineralized connective tissue containing collagen and non-collagenous proteins.
Collagen type I is the most important collagen protein in bone, making up 90% of the total collagen content.
Osteocalcin is the major non-collagenous protein in bone.
Osteonectin, a binder protein, binds to collagen in bone.

Osteoporosis

Osteoporosis is a progressive condition characterized by reduced bone mass and density.
Risk factors for osteoporosis include: aging, female sex, family history, sedentary lifestyle, caffeine and soda consumption, low intake of calcium, magnesium, and vitamin D, smoking, and corticosteroid use.

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