Cytoskeleton

At cell periphery along PM

Maintain cell shape

Cell-cell contact and signaling

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Throughout cytoplasm

Attach to basal membrane

Mechanical strength

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Throughout cytoplasm

Molecular trafficking

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Connect actin cytoskeleton of neighboring cells

Use classical cadherins (E-cadherin)

Lateral side of cell

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Structural stability

Connect IF of neighboring cells

Use desmoglein and democollin to bind to keratin in cell

Withstand tearing and shearing forces

Lateral side of cell

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Molecular trafficking: inhibits flow of molecules around cell

Can allow paracellular transport by loosening junctions

Claudin and occluden proteins

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Channels for molecules to flow between cells

Regulate electrochemical, chemical, and metabolic coupling

6 transmembrane proteins (connexins) make 1 connexon

Can open and close if cell damaged/ sick

Claudin

Occluden

Tough, flexible sheet of fibrous proteins

Under epithelium...provides anchor to CT

(1) laminin

(2) type IV collagen

(3) glycoproteins 

-fibronectin

Large and flexible protein in basal lamina

3 interwoven polypeptides linked by disulfide bonds

Head groups bind each other or collagen to form sheet-like network

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Found in basal lamina

3 protein strands loosely packed

N and C termini bind to one another or laminin to form mesh

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Epithelial cell adherence to basal lamina

V-shaped with 2 polypeptides joined with disulfide bonds

Can bind integrins, collagen, proteoglycans (heparin)

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(1) focal contact

(2) hemidesmosome

Link between epithelium and basal lamina

Use actin

Bind to collagen and fibronectin with integrin proteins

Link epithelium to basal lamina via IF

Bind to laminin using integrins

Transmembrane protein that binds to ECM proteins

Anchors epithelial cells

Dimer of alpha and beta

(1) collagen fibrils

(2) elastin

(3) proteoglycans

Type I and II

Tough--mechanical strength

Hydroxylation and crosslinking

(1) pro-alpha-chain spooled into ER lumen

(2)hydroxylate proline and lysine

(3) glycosylation 

(4) 3 pro-alpha-chains make a procollagen

(5) export procollagen to ECM

(6) cut procollagen loose ends--tropocollagen

(7) tropocollagens make a fibril

Synthesized by epithelial cells

Will become collagen fibril

Formed from 3 pro-alpha-chains

Will become collagen fibril

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Formed when secreted procollagen has loose end removed

Will become collagen fibril

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proline-->hydroxyproline

Requires Vit C

Hydroxyproline, proline, and glycine allow tropocollagen to make fibrils

lysine-(lysyl hydroxylase, Vit C)->hydroxylysine-(lysyl oxidase)->stable tropocollagen crosslinks

unstable crosslinks from lysyl oxidase only

Lack of Vit C--hydroxylases do not function making weak collagen fibrils since crosslinking in tropocollagen is weak

Unable to endure mechanical stress

Most sensitve: periodontal ligament and gingiva (remade often)

Component of basal lamina

Skin, blood vessels, lungs 

Hydrophobic monomers with extensive crosslinking

Molecular spring

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Component of basal lamina

Surrounds fibrous proteins

Carbohydrate rich, hydrated gel

Made of 

(1) hyaluronic acid

(2) adhesive glycoproteins

(3) proteoglycans--GAG

Part of ground substance

Core proteins linked covalenty via serine to polysaccharide chains of glycosaminoglycans (GAG)

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Glycosaminoglycans

GAG

Part of proteoglycans (ground substance)

Disaccharide repeats (amino sugar and acidic sugar)

Too stiff to be globular so form extensive expansion which attracts water and fills ECM

Sugars are sulfated and/or carboxylated

Negative charge attracts Na+ which attracts water-->molecular cushion (compression and nutrition to nonvascularized areas)

4 groups

(1) hyaluronan

(2) chondroitin sulfate

(3)heparan sulfate

(4) keratan sulfate

Longest GAG, part of proteoglycan-ground substance

Non-sulfated but still negative

not covalently linked to core protein, forms backbone of proteoglycan