ECM

Question 1

Components of lamina densa

Answer 1

Laminin

Type IV collagen, perlecan, nidogen

Question 2

Components of lamina lucida/rara

Answer 2

Fibronectin and laminin type 5, type 17 collagen from cell membrane

Question 3

Components of lamina reticularis

What lies right beneath the lamina reticularis?

Answer 3

Types 1,3 and 7 collagen, several proteoglycans, and

Stroma!

Question 4

Stroma is secreted by _____ and _____ and located beneath the ______ of the basement membrane of epithelial cells.

Answer 4

Stroma is secreted by FIBROBLASTS and SPECIALIZED MESENCHYMAL CELLS and located beneath the LAMINA RETICULARIS of the basement membrane of epithelial cells.

Question 5

Structural features of collagen:

____ present at every third amino acid

____, ____, and hydroxylated forms of these amino acids are present that also contribute to ____ _______.

Types of post-translational modifications:

1. Hydroxylation of ____ and _____
2. Extracellular _____ of lysine
3. Extracellular proteolytic cleavage of _____ and ______

______-ed pattern from ___nm fiber

Answer 5

Structural features of collagen:

GLYCINE present at every third amino acid

PROLINE, LYSINE and hydroxylated forms of these amino acids are present that also contribute to HELIX STABILITY.

Types of post-translational modifications:

1. Hydroxylation of PRO and LYS
2. Extracellular DEAMINATION of lysine
3. Extracellular proteolytic cleavage of N-and C- TERMINAL PROPEPTIDE EXTENSIONS.

STRIAT-ed pattern from 67nm fiber

Question 6

Fibril-forming collagens

Type _ : found in tendon, ___, ____, skin
Mutations in this type causes _______

Type _: found in ___
Mutations in this type cause _______

Type _: found in skin, aorta, stains with ____
Mutations in this type cause _______

Answer 6

Fibril-forming collagens

Type I : found in tendon, BONE, LUNG, skin
Mutations in this type causes OSTEOGENESIS IMPERFECTA

Type II: found in CARTILAGE
Mutations in this type cause CHONDRODYSPLASIA

Type III: found in skin, aorta, stains with SILVER
Mutations in this type cause EHLER’S DANLOS-TYPE 3

Question 7

Fibril-associated collagens (____) are type ___, which decorates outside of type ___ collagen fibrils

Answer 7

Fibril-associated collagens (FACIT) are type IX, which decorates outside of type II collagen fibrils

Question 8

Non-fibrillar, network-forming collagens are:
Type __ which are found in basal lamina
Type ____, which are ___ fibrils at ____-_____ tissue jcts
-Mutations in this type lead to blistering

Answer 8

Non-fibrillar, network-forming collagens are:
Type IV which are found in basal lamina
Type VII, which are ANCHORING fibrils at EPITHELIAL-CONNECTIVE tissue jcts
-Mutations in this type lead to blistering

Question 9

Transmembrane collagen consists of one type: Type ___, which connects ____ to ____ via _____ filaments.

Mutations in this lead to blistering.

Answer 9

Transmembrane collagen consists of one type: Type XVII, which connects BASEMENT MEMBRANE EPITHELIUM via ANCHORING filaments.

Mutations in this lead to blistering.

Question 10

Key intracellular events for collagen formation

1. ____ is removed
2. -OH added to ____ and____ to allow for intermolecular ______. If the ____ are mutated, there will be a problem in collagen assembly.
3. _______ is a required cofactor of the ________.
4. Addition of ____/____
5. ________ containing ___-rich globular domains guide _____ formation which begins in ____ in __–>__ direction.
6. Formation of ___ bonds between ____ and NH2 of ____ to COOH- groups on _______ leads to formation of helix.
   
   • ____-Pro required for stability of helix.
7. _______ have low Gly, Pro, and OH-Pro so do not allow for ____ formation WITHIN the cells.

Answer 10

Key intracellular events for collagen formation

1. SIGNAL is removed
2. -OH added to PRO and LYS to allow for intermolecular CROSS-LINKS. If the HYDROXYLASES are mutated, there will be a problem in collagen assembly.
3. VITAMIN C is a required cofactor of the HYDROXYLASE.
4. Addition of GAL/GLU
5. N/C TERMINAL EXTENSIONS containing CYS-rich globular domains guide HELIX formation which begins in ER in C–>N direction.
6. Formation of HYDROGEN bonds between PRO and NH2 of GLY to COOH- groups on SEPARATE leads to formation of helix.
   
   • OH-Pro required for stability of helix.
7. EXTENSION PEPTIDES have low Gly, Pro, and OH-Pro so do not allow for FIBRIL formation WITHIN the cells.

Question 11

Key Extracellular Events for Collagen Fibril Formation
1. Formation of _____ by cleavage of ______ on ___-forming collagens, which is done by ______. This leaves a bit of ______ domain for ____-_____.

2. Fibril assembly from _____ to ____, to _____. Covalent ____-____ of fibrils is catalyzed by ____-_____, a (__-dependent) enzyme that ____ Lysine. This enzyme is disrupted in some human diseases.

Answer 11

Key Extracellular Events for Collagen Fibril Formation
1. Formation of TROPOCOLLAGEN by cleavage of EXTENSION PEPTIDES on FIBRIL-forming collagens, which is done by PROCOLLAGEN PEPTIDASES. This leaves a bit of GLOBULAR domain for CROSS-LINKING.

2. Fibril assembly from MICROFIBRIL to FIBRIL, to FIBER. Covalent CROSS-LINKING of fibrils is catalyzed by LYSYL OXIDASE, a (CU-dependent) enzyme that DEAMINATES lysine. This enzyme is disrupted in some human diseases.

Question 12

Type IV collagen is component of lamina ____ and retains ______ at both ends. The _-termini of these monomers form ____, and _-termini form ___. This leads to _____ array.

Answer 12

Type IV collagen is component of lamina DENSA and retains EXTENSION PEPTIDES at both ends. The C-termini of these monomers form DIMERS, and N-termini form TETRAMERS. This leads to CHICKEN-WIRE array.

Question 13

Type VII collagens are made up of ____ which form networks of ____ ____ that connect lamina ____ to the matrix components in _____ or ____. _-termini of monomers interact with _____ while _-termini interact with type __ of ____ _____ or ____ plaques of stroma.

-Absence of this type leads to ____

Answer 13

Type VII collagens are made up of DIMERS which form networks of ANCHORING FIBRILS that connect lamina DENSA to the matrix components in LAMINA RETICULARIS or STROMA N-termini of monomers interact with EACHOTHER while C-termini interact with type IV of BASEMENT MEMBRANE or ADHERING plaques of stroma.

-Absence of this type leads to BLISTERING

Question 14

2 major components of elastic fibers:
______ elastin monomers and _____, which participates in _______. Mutations in this protein leads to _____ syndrome.

Assembly of elastic fibers is ______

Elastin can be visualized using the ____ stain.

Answer 14

2 major components of elastic fibers:
CROSS-LINKED elastin monomers and FIBRILLIN, which participates in CROSS-LINKING. Mutations in this protein leads to MARFAN syndrome.

Assembly of elastic fibers is EXTRACELLULAR

Elastin can be visualized using the ORECIN stain.

Question 15

GAGs are long, _____ polysaccharide chains. They consist of repeating _____ that contain alternating ______ + ____ acid.

Most important GAGs are: ______, _____ ______, _____ _____

All classes of GAGs except _____ are sulfated on ___ ____.

GAGs occupy ___ space.

_____ Syndrome is example of defective ____ of GAG.

Answer 15

GAGs are long, UNBRANCHED polysaccharide chains. They consist of repeating DISACCHARIDES that contain alternating AMINO SUGAR + URONIC acid.

Most important GAGs are: HYALURONIC ACID, CHONDROITIN SULFATE, AND HEPARAN SULFATE.

All classes of GAGs except HYALURONATE are sulfated on AMINO SUGAR.

GAGs occupy LARGE space.

HURLERS Syndrome is example of defective BREAKDOWN of GAG.

Question 16

Proteoglycans: _____ covalently bonded to ____ _____.

Main cartilage proteoglycan is _____, which is made up of 100 ___ ____ chains which are ____-linked to the ___ ____ at ___/____ residues. 60 ___ ___ chains have same linkages to ___ ____. Then, each chain is _______ attached by ___ proteins to a _________ backbone.

Answer 16

Proteoglycans: GAG covalently bonded to CORE PROTEIN.

Main cartilage proteoglycan is AGGRECAN, which is made up of 100 CHONDROITIN SULFATE chains which are COVALENTLY-linked to the CORE PROTEIN at SER/THR residues. 60 KERATAN SULFATE chains have same linkages to CORE PROTEIN. Then, each chain is NON-COVALENTLY attached by LINK proteins to a HYALURONIC ACID backbone.

Question 17

Heparan-sulfate proteoglycans: Can be _____ associated. Include members of ______ family. These PGs can bind ____ _____ and ___. It’s specifically known to bind a specifc ___ called ____ in order to maximize ____ activity for ____.

Can also be completely _____. Example: ____, which is localized to lamina ____ of basement membranes.

Answer 17

Heparan-sulfate proteoglycans: Can be MEMBRANE associated. Include members of SYNDECAN family. These PGs can bind MATRIX COMPONENTS and GFs. It’s specifically known to bind a specifc GF called FGF in order to maximize MITOGENIC activity for FGF.

Can also be completely EXTRACELLULAR. Example: PERLECAN, which is localized to lamina DENSA of basement membranes.

Question 18

Fibronectin is a matrix _____, made up of _ subunits connected by _______.

Soluble ____ form _______ and is involved in ______.

Oligomers attach to _____.

Fibrils are ______ in _____.

The ____ form are bound to _____, and their presence is inversely correlated with _____. I.e. Cells lacking FN would ___ ______, making for easier metastasis.

Can bind cell-surface _____ via ____ module in the FN.

Multiple _____ in modular array can interconnect series of ______ components at the surface and in the matrix.

Answer 18

Fibronectin is a matrix GLYCOPROTEIN, made up of 2 subunits connected by DISULFIDE BRIDGES.

Soluble DIMERIC form CIRCULATES IN SERUM and is involved in WOUND HEALING.

Oligomers attach to CELL SURFACE.

Fibrils are INSOLUBLE in STROMA.

The INSOLUBLE form are bound to FIBROBLASTS, and their presence is inversely correlated with TUMOR GROWTH. I.e. Cells lacking FN would LOSE ADHESIVENESS, making for easier metastasis.

Can bind cell-surface INTEGRINS via RGD module in the FN.

Multiple DOMAINS in modular array can interconnect series of CELL-MATRIX components at the surface and in the matrix.

Question 19

Laminin is a matrix _____ that has _ subunits, arranged in pattern containing _____ and ______.

Like FN, ____ domains and promotes _____.

Laminin-1 is located in [high] at lamina _____ and mediates interactions between cell surface and ______. It has a high affinity for type __ collagen and _____.

Type _ laminin is located in ___ _____ immediately adjacent to ____ cells in the lamina _____ and binds to ____ receptor _____ on the epithelial surface.

Binding to major integrin distinct from FN occurs through RGD.

Answer 19

Laminin is a matrix GLYCOPROTEIN that has 3 subunits, arranged in pattern containing 1 LONG ARM and 3 SHORT ARMS.

Like FN, MODULAR domains and promotes ADHESION.

Laminin-1 is located in [high] at lamina DENSA and mediates interactions between cell surface and BASEMENT MEMBRANE. It has a high affinity for type IV collagen and PERLECAN.

Type 5 laminin is located in ANCHORING FILAMENTS immediately adjacent to EPITHELIAL cells in the lamina INTERNA and binds to INTEGRIN receptor A6B4 on the epithelial surface.

Binding to major integrin distinct from FN occurs through RGD.

Question 20

Nidogen is a matrix _______ that’s also known as _____. It’s ____ Shaped and binds to ______ and type __ collagen. It mediates interaction between these 2 molecule in lamina ____.

Answer 20

Nidogen is a matrix GLYCOPROTEIN that’s also known as ENTACTIN. It’s DUMBBELL Shaped and binds to LAMININ 1 and type IV collagen. It mediates interaction between these 2 molecule in lamina DENSA.

Question 21

Integrins are ____ which binds ___, ____, ____ and other cell adhesion molecules. The ___ AA sequences of many matrix components are important for this binding. Integrins are found on ___ and ____ cell surfaces and also on some ________.

Upon binding, _____ regulate the activity of _____ such as _____ that allow several _____ _____ ____ to assemble.

Integrins also bind _____-associated protein to serve to link the ____ and ____.

Answer 21

Integrins are DIMERS which bind FN, LAMININ, COLLAGEN and other cell adhesion molecules. The RGD AA sequences of many matrix components are important for this binding. Integrins are found on EPITHELIAL and MESENCHYMAL cell surfaces and also on some CIRCULATING BLOOD CELLS.

Upon binding, INTEGRINS regulate the activity of KINASES such as FAK that allow several INTRACELLULAR SIGNALING PATHWAYS to assemble.

Integrins also bind CYTOSKELETAL-associated protein to serve to link the ECM and CYTOSKELETON.

Question 22

A5B1 integrins link ____ to ____ probably through ____.
-it’s a co-receptor with others that lead to _____ of ____ and ____.

A6B1 is a major receptor for _____ and may be altered in some forms of ___ ____.

A6B4 is part of _____, which anchors _____, not actin.

Answer 22

A5B1 integrins link FN to ACTIN probably through TALIN.
-it’s a co-receptor with others that lead to PHOSPHORYLATION of PAXILLIN and FAK.

A6B1 is a major receptor for LAMININ and may be altered in some forms of MUSCULAR DYSTROPHY.

A6B4 is part of HEMIDESMOSOMES, which anchors KERATIN/INTERMEDIATE FILAMENTS, not actin.

Question 23

___ integrin receptors are found on platelets, which binds ___ during clotting. _____ disease results from absense of these receptors.

Answer 23

B3 integrin receptors are found on platelets, which binds FN during clotting. GLANZMANNS disease results from absense of these receptors.

Question 24

___ integrin is found on WBCs. ____ ____ deficiency prevents binding of WBCs to ____.

Answer 24

B2 integrin is found on WBCs. LEUKOCYTE ADHESION deficiency prevents binding of WBCs to ENDOTHELIUM.

Question 25

Affinity of a given integrin for it’s ligand can change:

In ____ adhesion to endothelium, initial interaction is through a different low affinity receptor ____. ___ ____ alters integrin conformation by _____ of _____ tails which then allows ____, _______ binding to endothelium, and ultimately ________ will occur.

Regulation of affinity of integrins in ____ ensure that ____ only form in appropriate environment when ____ is needed.

Answer 25

Affinity of a given integrin for it’s ligand can change:

In LEUKOCYTE adhesion to endothelium, initial interaction is through a different low affinity receptor SELECTIN. INTRACELLULAR SIGNALING alters integrin conformation SEPARATION of CYTOPLASMIC tails which then allows SPECIFIC, HIGH-AFFINITY binding to endothelium, and ultimately INFILTRATION will occur.

Regulation of affinity of integrins in CLOTTING ensure that CLOTS only form in appropriate environment when CLOTTING is needed.

Question 26

Melanoma cell line defective in specific ____ integrin is highly ____. Can be reversed by ______ of normal __ ____subunit.

Answer 26

Melanoma cell line defective in specific ALPHA integrin is highly METASTATIC. Can be reversed by TRANSFECTION of normal ALPHA subunit.