CEllBIO

Glycocalyx & ECM

• Cell cell interactions
• Cell-substratum interaction
• Mechanical protection
• Barrier
• Receptors/signaling

"Cell Coat"

• Collagens
• GAGs (glycosaminoglycans)
• proteoglycans
• preteoglycan aggregates
• EC adhesions proteins ( fibronectin & laminin)

• ECM of animal cells
• 50 - 200nm

• Type IV Collagen (don't bundle, nonfibrillar) 2D
• Laminin (2D with IV collagen)
• Perlecan (a preteoglycan) crosslinks ECM --> PM
• Entactin (crosslinks with other components above)

• Mechaincal support
• Maintance of epithilial polarity (brush tip)
• Separtes ajacent tissue
• Substrate for cell migration (molecular highway)
• selectively permeable barrier

• Some cancer cells show altered binding to basal lamina, premitting their passage and allowing them to migrate throughout the body
• process = metastasis

• Most abundant human/animal protein (>25%)
• High tensil stregth fibrous glycopreoteins
• Provides stregth support and protection noted in, cartilage, bone, tendon and skin

• Secreted by
• fibroblasts(+other connective tissue like osteoblasts of bones)
• Smooth mucles cells
• epithelial cells

• 3
• a-chain(a collagen chain)

• Rod like
• coiled coil
• 300

Collagens can be heterotypic..like alloys with different mechanical and structural properties

Lysine and hedroxylysine

Much larger, and thicker

eg. collagen fibers of tendons results from parallel bundles of fibrils

• Present in Basement Membranes (basal lamina)
• Does not form fibrils, making making it paticularly flexible

• Osteogensis imperfect ( Love you adam!)
• --- Type 1 colalgen disorder
• --- fragile bones

• Ehlers-Danlos Syndrome (Elastic Skin)
• --- Defect in a variety of collagen
• --- Hyperelastic skin
• --- Organs can somtimes rupter
• --- Famous man = James Morris

• Alport Syndrome
• --Type IV collagen dissorder(not fibriler, forms webs)
• -- Kidney dysfunction due to glomerular basment membrane
• --->kidney failure, blood + proteins in urine

• each of the 3 pollypeptide chains is LH (3 a.a/turn)*
• The pollypetide chain all together is RH helix

• Long neg-charged polysaccharides composed of repeating dissacharid units.
• 1 monosaccharide of which is always an amino surgar
• acidic and hydrophilic (helps proteoglycans form hydrated gels *ear)

• Golgi
• core protein
• proteoglycans

• Chrondriotin Sulfate
• Keratan Sulfate
• Hyaluronic acid ( only non-sulphated)

Non-covalently

Protein-glycoaminoglycan complexes formed by covalently linkage of GAGS to core proteins

• Freely soluble
• -- eg, aggrecan
• --- Major structural component of cartilage
• GPI-Linked
• --eg. Glypican--- family of heparen sulphate proteoglycans
• Transmembrane
• -- act as FGF corectors with CPCRs
• eg. syndecan

• A core protein found in Proteoglycans
• FCF coreceptor
• only 3-5 GAGS (short)

• Complement each other making tissue stronger
• Proteoglycans offer ressitance to deformation
• Collagens offer ressitance to pulling forces

Helps define shape of tissue

Long feather GAG chains help to filther out microbes and viruses in the ECF before the reach the cell surgace

Diffusion of small molecules near the surgace of the cell to help keep cells hydrated!

Preteoglycans bind to other protein sin the ECF, affecting the ability of those proteins to bind to the surface of cells

• eg. preteoglycans can sequester(hide) growth factors like FGF
• May also act as corectors

(Hold then release at a later date vs formation change upon bonding with heparan sulfate (preteoglycan))

• Extra Cellular adhesions proteins (multiadhesive)
• Bind and Crosslink -- ECM components (eg collagens)
• Bind and Crosslink-- cell membrane proteins (eg. integrins)
• Serves as intermediate between cells and other ECM molecules

Help form complex molecular networks (especially laminins)

Consisting of many different binding domains

Characateristic of Fibronectin & Laminins

Fibronectin & Laminin

2 polypetides linked by disulphide (SS) bridges between cysteines

• 3 different polypetides (heterotrimers) linked by SS bridges
• Coiled structure

• Tripeptide sequence motif (reaccuring sequence)
• Present in Laminin and fibronectin
• Common in ECM proteins
• Recognized and bound by integrins

• Claudins
• tight junctions
• Cadherins
• adherens junctin
• desmosomes
• Connexins
• gap junctions
• Integrins
• hemidesmosomes
• focal adhesion

• Cadherins
• Selectins
• (Ig-like cell adhesions molecules)
• Integrins
• integral membrane proteoglycan
• structural glycoprotein
• proteoglycan

• Transmembrane glycoproteins
• Heterodimeric (composed of both a alpha & beta chain)
• Only In animals
• Most important class of CAM that link cells to proteins of ECM and control the cells reponse after adhesion

• Homophilic interactoin (8 interactions Cell-cell)
• nonjunctinal adhesive complexes between cells
• heterophilic interactions
• Nonjunctin adhesion to ECM
• Junctional adhesive complexes
• indirectly link the cytoskelton ECM

Heterophilic interactions are with ECM companants of other molecules then other integrins ( eg. collagen, laminin, fibronectin etc)

• Complex
• Some bind to RGD sequence motif
• Some recognize and bind lingands that lack RGD (non RGD recognition)

Symthetic RGD peptides and nonpeptide RGD analogies have been used to inhibit the formation of fibrogen bridges between platelets, inhibiting bloof clot formation

Affinity: modulate the strength of adhesion between integrins

Avidity: modulate number of integrin molecules involved

• Begins in cell, causes effects outside cell
• can modulate affinity and avidity of integrins

• 1) inactive bent
• 2) Talin binds (beta)
• 3) Active (straight)
• 4) Affinity modulation (change in shape)
• 5) Avidity modulation ( Increase in # of molecules)
• 6) Complmentary
• 7) Both increase strength of adhesion

Avidity modulation

• The binfing of EC ligands which alter the cytosolic interaction of integrins with cytoskeleton components
• --> Alter the activity kinases
• --> leads to changes in extant protein activity or even gene expression

• Single transmembrane spanning domain
• Conserved cytosolic C-terminus (involved in binding B-catenin)
• 5 extracellular domains
• Often found as cluster of dimers

Dimers engage in variable interdigitation with similar cadherins on neighbouring cells

Ca⁺⁺

• 1) downregualtion of cadherins
• 2) down strength of adhesions
• 3) allows cancer cells to invade tissue

• Embryonic tissue formations (compact tissue)
• Metastasis
• Adhesion of epithelial cells (adherens junctions, desmosomes)
• Adhesions of other cell types (adhesive complezes that hold neurons to each other)

Clusters of intergins that link ECM to actin microfilaments of the cytoskeleton

• Muscles and tendon
• as well as commonly in vitro

• Focal adhesion
• ex. fibroblasts attached to teh surfface of a coated culture dish are not uniformly attached

• Assemble / Disassemble
• Focal Complexes

Used to realease cell from the coated dishes when subculturing

• interact directly with intergrins
• indirectly eith Talin and Paxillin

• Changes in extant protein activity
• Changes in gene expression

• Clusters of interins that link basement membrane to intermidiate filaments of cytoskeleton.
• eg. keratins of epithlial tissue
• Vimentins of connective tissue

Tightest Attachment of Cell & ECM

• Autoimmune blistering disorders
• eg.bullous pemphigoid
• skin detaches allowing space to fill with ECM aka blister)

• eg. epidermolysis bullosa
• inside & outside blisters
• results in extreamly fragile skin

Gate and fence function

• Form a gasket like seal around adjacent animals cells @ apical aspect of adjacent epithial cells
• Mediated by transmembrane proteins claudins

• blood brain barrier between endothelial cells of capillaries
• Prevent water loss by skin to environment

Dirst to demonstrate that skin epithelial cells have tight junctions

• Devloped mice lacking Claudin1
• Lead to dehydration and death shortly after birth

• Paracellular (inbetween cells)
• Gate function

• Clusters of cadherins
• indirectly link bundles of cytoskeletal actin microfilaments between adjacent epithelial cells and cardiac muscles

Enable mechanical, chemical and electrical connectivity between cells.

• Adherens junctions
• desdomones
• gap junctions

All which indirectly link sarcomere (contratile unit) microfilaments of adhacent cardiac muscles

adpater protein catenins mediate indirect linkage of cadherins and microfilaments.

B are linked to cytosolic C-termini of cadherins

a links to B-caternin microfilaments

• Cell adhesions,
• shape change
• Singalling
• link the intergrins of focal adhesion
• Cadherins of an adheren junction provide for "outside in" signalling

(form adhesion belts around cells"

• Spot welds between cells ( great strength)
• clusters of cadherins that indirectly link bundles of intermediate filament etween adjacent cells

• Keratins (between ajacent epithlial cells)
• Vimentin (connective tissue and muslcle tissue)

Plakoglobins and desmoplakins

• Are subject to mechanical stress
• eg, Gingina, cardiac muscles

• Pemphigus vulgaris
• Autoimmune blistering disorder

• Clusters of channels
• allow commuication between adjacent animal cells

• Share electrical signals (between cardiac muscle cells)
• ion flow at electrical synapses
• Metabolic cooperation (sharing important metabolites)

Connexons composed of 6 connexins

• 1200
• 2000

• -well coordinated responses
• -Synchronous contraction of carfiac myocytes
• -Coordinated unidirection beating of cilia along tracheal epithelial cells
• -Uterine smooth muscle contractions during birth
• -Rapid reflex reactions

• pH
• PKC (phosphorylation by protein kinase C)
• Chages ins cytosolic [Ca⁺⁺]

(closed when high cytosolic Ca concentration, protective)

• Communication junctions between PLANTS
• transport proteins
• 30-60 nm traffic
• full dialated 50kDa proteins

opening lined with plama membrane

• Adhesion molecules
• Cell walls

• Maintance of wall pressure
• Mechanical support
• Protection from abrasion, pathogens, osmotic influx
• Mediate cell interactions
• Barrier to large molecules

• Like reinforced gel
• Cellulose (fibrous element)
• Pectin, hemicelluloses ( gel-like matrix)

• glc-B(1-4)Glc
• organized in microfibrils
• rigidity
• resists tensile forces

• Branced polysaccharides
• Form crosslinks to cellulose microfibrils

• Heterogenous class of negativelely charge polyssacharides
• Form hydraded gels like GAGs
• Act like molecular sieve
• role in defence