fibrillar proteins (extracellular matrix)

Question 1

list prupose and components of the extracellular matrix. What is the connective tissue between the cells

Answer 1

Ground substance-the extracellular items that are located in connective tissue

1. collagens
   
   1. provide tensile strength
2. elasticfibers, proteglycans, hyaluron
   
   1. provide the resilience of tissue
3. glycoproteins
   
   1. mediate adhesive interactions between other matrix molecules or between cells and matrix molecules.

Question 2

Describe the homeostasis of the extracellular matrix

1. synthesis
2. optimization
3. communication
4. response to damage

Answer 2

dynamic interaction between the cells and the exrtracellular matrix order to maintain the functino of the tissue.

1. sythensis
   
   1. resident cells synthesize the extracellular matrix
2. optimization
   
   1. the extracellular matrix provides an optimal environment for the cells
3. communication
   
   1. cells bind to extracellular matrix molecules through cell surface receptors
   2. receptors allow the cells to sense changesin the extracellular matrix and respond accordingly
4. response to damage
   
   1. if the tissue is damaged, the primary response of the cells is to restore the integrity of the tissue by re-synthesizing the extracellular matrix.

Question 3

Jims pathology report showed the cancer was secreting molecules remoldeling the extracellular matrix. What are these agents, how do they opperate and what will happen if this cancer cell is not properly put under control?

Answer 3

cells can secrete and interact with the matrix to impose

1. tissue differentiation(matrix composition changes)
2. cell migration (cells have to move through the matrix)

agents

1. MMPs
   
   1. metalloproteinases (MMPs, Zn2+)
   2. function
      
      1. secreted by cells to degrade the matrix proteins
2. TIMPs
   
   1. Tissue inhibitors of MMP
   2. function
      
      1. regulate the activity of remodeling
3. these have a ratio in the matrix. if MMPs/TIMPs was to tip in either direction the cancer could remodel the environment and invade the surrounding tissues.

Question 4

define the imperitive collagens, structure and functions.(general)

Answer 4

1. function
   
   1. stabilize the extracellular matrix via heabily crosslinked
2. structure
   
   1. triple helical structure (dont confuse with DNA double helical structure)
   2. Gly-X-Y repeats
      
      1. x= proline, frequently
      2. y=hydroxyproline frequently
      3. these repeats favor triple helix formation
3. major groups
   
   1. fibril forming-types1-3
      
      1. types-subunits
         
         1. 2-a1 and 1-a2
         2. 3-a1
         3. 3-a1
   2. network forming (form meshes)
      
      1. type4 only
         
         1. 6 different alpha chins

Question 5

describe/define biosynthesis of fibrillar collagen synthesis. what is the process in step three and example of?

Answer 5

1. location
   
   1. synthesis of procollagen chains occur in the rER
2. protein modification
   
   1. co-translational modification
      
      1. certain proline and lysine residues are hydroxylated into hydroxyproline and hydroxylysine
         
         1. crutial for stability of triple helix. provides a structural stability.
   2. post translational modification
      
      1. some hydrocylysines can be glycosylates
3. the triple helix forms in the rER
   
   1. formation proceeds from the C->N terminal
4. triple helix is held together by H-bonds
5. propeptides are cleaved off after procollagen is secreted into extracellular space
6. the enzymes that cleave procollagen are “N and C procollagen peptidases”
7. once the propeptides are cleaved off, collagen triple helices assemble into fibrils.

Question 6

describe the precursor generation to collagen

Answer 6

a collagen chain is first synthesized as procollgen

1. the propeptides are removed extracellularly by proteolytic digestion afterthree procollagen chains are assembled into a triple helical structure

Question 7

describe the orientation of the collagen fibers in the ECM

1. association
2. bond

Answer 7

1. staggering
   
   1. fibrils are formed from collagen triple helices that associate is a staggered manner
   2. produces a characteristic striated pattern of collagen when viewed under a microscope
2. covalent crosslinking
   
   1. collagen fibrils are stabilized by covalent crosslinking between collagen monomers

Question 8

How is collagen stabalized? three specific processes. list mechanism and all the enzymes, substrates, products and locations.

Answer 8

stability of collagen

1. H-bonds
   
   1. hydroxyproline manages triple helix quarternary structure
   2. prolyl hydroxylase
      
      1. generates hydroxyproline in rER
      2. requires Fe2+ and vitamin C (ascorbic acid) as cofactors
2. crosslinking
   
   1. Oxidation of lysine and hydroxylysine
      
      1. the covalent crosslinks within collagen fibers are created through formation of oxidized lysine and hydroxylysine residues
      2. Lysyl oxidase - catalyzes the oxidation of lysin and hydroxylysine in the extracellular matrix.
         
         1. the allysine residue spontaneously react with lysine/hydroxylysin/allysine/hydroxyallysine residues to create covalent crosslinks between collagen chains
      3. generating hydroxylysine
         
         1. hydroxylysine manages the crosslinking in the ECM
         2. lysyl hydroxylase generates hydroxylysine
         3. lysyl hydroxylase requires Fe2+ and vitamin C(ascorbic acid ) as cofactors

Question 9

describe the synthesis of Type 4 collagen formation. similarities and difference to type 1-3

Answer 9

assembly of the type 4 collagen network

1. type 4 collagen is the main basement membrane collagen
2. in the extracellular space, two ttype 4 triple helices at their C-terminal, forming a dimer
3. dimers associatet through their N-terminal ends to form tetramers and eventually a large network, similarto chicken wire

Question 10

Jerry has a horrible diet and only eats processed low vitamin foods. He presents to his doctor with loose teeth and eccymosis on his legs.

What is the suspected disease, biochemical mechanism, clinical presentations, and cause to the illness

Answer 10

1. Hypovitaminosis-Scurvy, general CT disease
2. biochemical disease
   
   1. prolyl and lysyl hydroxylases are not efficient
   2. the collagen triple helix is less stable and crosslinking is also reduced
3. clinical presentation
   
   1. bruises on skin
   2. bleeding gums, loose teeth
   3. delayed wound healing
   4. bone and joint abnormalities
4. cause
   
   1. lack of fruits and vegetyables in the diet leading to a decrease in ascorbic acid uptake. Vit-C is a critical cofactor in the enzymatic role of prolyl and lysylhydroxylases.

Question 11

Mary has the following has the following in utero screen. The doctor performs genetic test with the following result. alpha-1 chain has a subtitution mutation (Gly->Tryp).

what is the suspected disease, mechanism, types (include discrpancies), clinical symptoms

Answer 11

osteogenesis Imperfecta (OI) photo shows in utero arm fracture

1. mechanism
   
   1. the mutation to a bulky side chain amino acid disrupts the sterical stability. this substitution does not support the 4’ triple helix structure.
2. seven type
   
   1. 1-4
      
      1. associated with Type 1 collagen mutations
3. discrepancies
   
   1. type 1 OI
      
      1. reduced number of collagen fibrils
   2. type 2-4 OI
      
      1. defective collagen fibrils
4. clinical symptoms
   
   1. increased incidence of fractures
   2. short stature
   3. grey or brown teeth that wear down easily(dentinogenesis imperfecta)
   4. blue sclera- due to tissue thinning allowing underlying pigment to show through

Question 12

Ehlers-Danlos generates hyper extensive skin.

list the mechanism affected, the various forms and their associated mutations, and clinical presentations.

Answer 12

1. this disease manifests from the deficiency of collagen processing enzymes. The collagen does not make it to the matrix or is not processed completly.
2. types
   
   1. classic type
      
      1. mutation
         
         1. type 5 collagen-fibril associated collagen
      2. presentation
         
         1. hyperextensive skin
         2. delayed wound healin, atrophic scars
         3. joint hypermobilit
   2. vascular type
      
      1. mutation
         
         1. type 3 collagen-highly concentrated in arteries
      2. presentation
         
         1. arterial, intestinal and uterine ruptures.
         2. the most lethal types
   3. kyphoscoliotic type
      
      1. mutation
         
         1. lysyl hydroxylase
      2. presentation
         
         1. hyperextensive skin
         2. delayed wound healing, easy bruising, thin scars
         3. joint hypermobility
         4. progressive scolliosis
         5. increased risk of vascular rupture

Question 13

A 2 year old boy presents to a physician with hearing loss and renal insufficiency (protein and blood are found in urine). What disease could lead to this clinical presentation? define the mutation locatin, biochemical and reasoning to clinical manifestations.

Answer 13

alport syndrom-type 4 collagen related nephropathy

1. mutation
   
   1. type 4 collagen gene
2. biochemcial
   
   1. basement membrane
   2. glomerular membrane and Organ of Corti are at risk for detachment.
3. presentation
   
   1. renal insufficiency
      
      1. hematuria
      2. proteinuria
   2. sensorineural hearing loss

Question 14

describe function, location and making of elastin

Answer 14

elastin

1. function
   
   1. major component of elastic fibers, allowing tissues to stretch and contract
   2. strretching force
      
      1. amorphous fiber is stretched to expose the hydrophobic regions to the aquesous enviornment. The decreases the entropy of the water as it needs to rearrange to conform to the regions.
   3. half life of 70 YEARS!!!!!! AMAZING
2. location
   
   1. widespread
3. made
   
   1. synthesized in the ER and secreted as a monomer
   2. in the ECM, lysine residues are oxidized by lysyl oxidase then spontaneously form cross bridges between elastin monomers
      
      1. lysine-> allysine or hydroxylysine->hydroxyallysine, then spontaneously react to form mesh in ECM
   3. correct assemly of elastic fiber requires microfibrils formed by fibrillins

Question 15

Betty has smoked for 46 years and has developed emphysema. Her lung biopsy should neutrophil count was 6x’s its normal level.

What can you explain about the findings? Function and disease manifestation

Answer 15

disease= alpha1-antitrypsin deficiency

1. function
   
   1. a1-antitrypsin
      
      1. natural inhibitor of neutrophil proteolytic enzyme (elastase), and is responsible for preventing excessive degradation of elastin
2. disease manifestation
   
   1. a1-antitrypsin deficiency leads to lower elastin content. This leads to collapseof small airways when the patient exhales.
3. mechanism
   
   1. elastin has many repeaing hydrophobic areas. when amorphous elastin chain structure is stretched and exposed to the aquesous enviornment, the water decreases in entropy as it needs to organize itself aroung the hydrophobic moieties.
4. 1. condition is exacerbated in smokers
      
      1. breathing in of foreign material increases the [neutrophil]. increaseing elastase

Question 16

President Lincoln was very tall and had a disease associated with fibers of the ECM.

Name the disease, its affects on skeletal, cardiovascular

Answer 16

marfan syndrome

1. cause
   
   1. mutation in fibrillin-1 leads to defective microfibril formation of elastic fibers
2. manifestation
   
   1. skeletal
      
      1. very tall stature, kyphoscoliosis
      2. disproportionally long limbs, fingers and toes
      3. hyperflexible joint
   2. cardiovascular
      
      1. dilation and rupture of the aorta
      2. heart valve problems
   3. ocular
      
      1. dislocation of the lens of the eyes (ectopia lentis)

Question 17

List two important receptors for ECM cells to maintain communication with the matrix. What does this interaction form?

Answer 17

1. cells interact with the matrix through receptors
   
   1. relationship of receptors
      
      1. integrins (ab dimer)-belong to enzyme-linked (associated with kinases)
         
         1. anchor the cells to the ECM
      2. laminin
         
         1. structure
            
            1. heterotrimers
               
               1. a,b,y chains. stabalized by disulfide bonds.
            2. synthesis in ER, assembly in golgi
         2. function
            
            1. bsement membrane proteins.
            2. interact with other basement membrane proteins and integrins on the cell surface
         3. bind to collagens and glycoproteins
   2. integrin-laminin
      
      1. interactions are essential for the correct formation of basment membrane

Question 18

A woman bring her son in to the ER, who presents with blisters and patches of skin missing. The mother says they just appeared, and they keep happening all over the body.

Answer 18

Juntional epidermolysis bullosa-lamin and/or integrin deficiency

1. cause
   
   1. mutation in certain laminins and integrins
   2. mainly affects the basement membrane below the epidermis and mucosal membranes
2. symptom
   
   1. fragile skin that shows extreme blistering, epidermis seperates from dermis

Question 19

define the 5 main components of the ECM give their function and examples

Answer 19

1. main components and function
   
   1. collagens
      
      1. provide the tensile strength
      2. example
         
         1. type 1,2,3,4
   2. elastic fibers
      
      1. provide resilience
      2. example
         
         1. elastin (monomer)
         2. fibrillin(microfibril required for correct assembly of elastin)
   3. proteoglycans
      
      1. provide resilience
      2. example
         
         1. GAG
   4. hyaluronan
      
      1. provide resilience
   5. glycoproteins
      
      1. mediate adhesive interactions between other matrix moleucles or between cells and matrix
      2. example
         
         1. integrin and laminin

Question 20

list collagen based on its location and function.

Answer 20

1. type
   
   1. fibril forming
      
      1. skin, bone, tendon, blood vessel, cornea
      2. cartilage, IVD, vitreous body
      3. blood vessels, fetal skin
   2. network forming
      
      1. 4-bsement membrane
      2. 5-beneath stratified squamous epithilia

Question 21

List diseases associated with collagens and mutation.

Answer 21

colagen malformation

1. type-OsteoImperefcta(OI)
   
   1. ​mutation in type 1 collagen
2. type- ehlers danlos(EDS)
   
   1. classic type
      
      1. mutation in type 5 collogen
         
         1. fibril associated-network forming
   2. vascular type
      
      1. mutation in type 3 collagen
         
         1. fibril type
   3. kyphoscolitic type
      
      1. mutation in lysyl hydroxylase
         
         1. the enzynme that catalyzes the P->hydroyproline, which assists with crosslinking in the ECM
3. type-Alport syndrome
   
   1. mustation in the type 4 collagen
      
      1. important for basement membrane