4 families of ECM
- Collagen
- Elastin
- Glycoproteins
- Proteoglycans
2 types of glycoproteins
- Fibronectin
2. Laminin
Collagen is ___% of total body ____?
30%
Protein
Structure of collagen = _______
Stabilized by ________
Triple-helical
Crosslinks
Synthesis of collagen is affected by ____
Physiologic conditions (ex. diet or mechanical stress) [Frequently remodeled]
A genetic mutation that causes the _____ in ___ collagen to be replaced by another AA is called _____ ____
Glycine
Type I
Osteogenesis/dentogenesis imperfecta
Predominant ECM molecule in blood vessels
Elastin
ECM component found in skin, lungs, intestines
Elastin (found in organs that require elasticity)
Elastin is stabilized by ____
2-way crosslinks
How long is elastin synthesized for
Stops after adolescence
Function of fibronectin
Facilitates communication btwn IC and ECM Cell adhesion Cell growth Migration Wound healing
Fibronectin binds to _____
Other ECM molecules & integrin molecules on cells
Types of fibronectin
At least 20 known types including soluble and insoluble forms
Fibronectin produced by
Alternative splicing of a single precursor mRNA
Where is laminin primarily found?
Basal lamina
Function of laminin
Gives structural support to ECM
Major component of basement membranes in epithelial and muscle tissues
Laminin
Laminin binds to cells via _____
integrin family of proteins
Diseases of defective laminin
Muscular dystrophy
Defects of kidney filter
Epidermolysis bullosa - lethal skin blistering disease
Proteoglycans are the __-___ of the ECM
gel-formers
Proteoglycans have many ____ charges which attracts ____ & ____. Result is ____ of ECM that provides ____ & _____
Negative Cations Water Hydration Rigidity Durability
Proteoglycans make up ___% of ECM proteins, but because of _______, ___ ____ fill most of ECM
<10%
hydrophilicity
GAG chains
Proteoglycans can combine to form _____
aggrecans
Other functions of proteoglycans
Can bind growth factors
Regulate enzyme activity
Act as co-receptors
Types of diseases caused by proteoglycan defects
Lysosomal storage diseases
3 types of cell junctions
- Tight junctions
- Anchoring junctions
- Gap junctions
Types of anchoring junctions
Adherens junctions
Desmosomes
Hemidesmosomes
Focal adhesions
This type of tissue is particularly rich in cellular junctions
Epithelial tissues
Type of cell-cell junction found in all epithelia
Tight junctions
Tight junctions _______ intercellular permeability and ______ cell membrane polarity
Severely limit
Maintain
Tight junctions are formed by
Sealing strands anchored in the membrane
Tight junctions permeability to macromolecules and small molecules
Active transport required for solutes to cross epithelial barrier
Junctions are impermeable to macromolecules
Permeability to small molecules varies greatly depending on the # of sealing strands and transmembrane proteins (occludin and claudin families) that comprise them
Anchoring junctions bind what and are found where
Bind cells to each other and to ECM
Found in all tissues, especially those subject to mechanical stress
Adherens junctions are found primarily in ____
epithelia
Adherens junctions form a continuous ____ ___ and are required for _____ _____ formation and ____ ____ formation in _____
Adhesion belt
Tight junctions
Epithelial tube
Morphogenesis
Transmembrane proteins in adherens junctions and desmosomes
Cadherins
Adherin junctions connect bundles of ____ filaments (_____)
Actin
Contractile
Desmosomes are found primarily in _____
Epithelia and muscle cells
Desmosomes contribute to
Tissue strength & durability
Hemidesmosome function
Bind cells to ECM
Attach junctional epithelium to tooth enamel
Transmembrane proteisn in hemidesmosomes
Integrins
Focal adhesions functions
Spot-type junctions that link cell cytoskeleton to ECM Important in Cell migration Motility Differentiation Proliferation Orthodontic tooth movement
How many proteins can focal adhesions contain
As many as 100
Response of focal adhesions to IC or EC signals
They can form, change, or disappear in response (Dynamic)
External mechanical signals are transmitted via
Integrin receptors in focal adhesions
Gap junctions are found primarily in _________
All cells except skeletal muscle and blood cells
Gap junction permeability
Allow small molecules and electrical charges to pass directly from cell to cell
Varies with the identity and combination of connexins present
Gap junction permeability regulated by
Intra- and extra- cellular signals
Channels in gap junctions are called ____ and are ____ of ____ proteins
Connexons
Hexamers
Connexin
Gap junctions main function
Allow cells of a given tissue to function together quickly and in a coordinated fashion