Extracellular Matrix and Cell-Cell Interactions Flashcards
What is the function of the extracellular matrix?
Fills the spaces between cells and binds cells and tissues together
What are epithelial tissues?
thin, sheet-like extracellular matrix (basal lamina) that underlies epithelial cells and binds them to underlying connective tissues
What are muscle, adipose, and nerve tissues surrounded by?
A thin basal lamina
What are some examples of connective tissues?
bone, tendon, cartilage, and loose connective tissue underlying skin
What are extracellular matrices composed of?
Tough fibrous structural proteins embedded in a gel-like polysaccharide material known as ground substance
What do specialized adhesion molecules do?
anchor cells to the extracellular matrix
What is collagen? How many types of collagen are there?
Collagen is the major structural protein of the extracellular matrix, of which the family contains at least 27 different members.
What is the repeating amino acid primary sequence of collagens?
A triple repeat of Gly-X-Y, where X is usually proline and Y is usually hydroxyproline (could also be hydroxylysine)
What do the repeat structures of collagens form?
Form triple helices with three polypeptide chains wound around each other
How are collagen fibrils formed? Where does this assembly take place?
triple helices line up in staggered arrangement and are cross-linked together.
takes place within the ECM following the secretion of procollagen from the cell via the ER/Golgi pathway.
What is the structure of network-forming collagens?
network-forming collagens have numerous interruptions of helical regions that are cross-linked together (more flexible)
What is elastin?
The principle protein of elastic fibres, cross-linked into a network by covalent bonds
What are glycosaminoglycans (GAGs)?
Gel forming polysaccharides of the extracellular matrix that consist of repeating units of disaccharides
How do GAGs create a hydrated gel-like structure?
negative charges bind positively charged ions, attracting and trapping water molecules
How do GAGs form proteoglycans?
Covalently link to specific proteins to form proteoglycans
How are larger proteoglycan aggregates formed?
A number of proteoglycans interact with hyaluronan chains (GAGs) to form large complexes in the ECM
What are matrix adhesion proteins responsible for?
Linking the components of the matrix to one another and to the surface of cells.
What is fibronectin?
The principal adhesion protein of connective tissues
What is laminin?
The principal adhesion protein of the basal lamina
What is nidogen?
A protein that links laminin to collagen type IV
What are integrins?
the major cell surface proteins responsible for the attachment of cells to the extracellular matrix, and serve as anchors for the cytoskeleton within the cell.
What do integrins consist of?
Dimers of one alpha and one beta subunit
What is focal adhesion?
A type of cell-matrix junction that is linked to actin filaments and attaches a variety of cells to the extracellular matrix
What are hemidesmosomes?
A type of cell-matrix junction linked to intermediate filaments that mediate epithelial cell attachments at which specific integrin interacts with laminin at the basal lamina
What do adherens junctions involve? How do they work?
Involves a family of integral plasma membrane proteins in adjacent cells known as cadherins.
cadherins link to the actin cytoskeleton intracellularly via catenind, and extracellularly with each other.
What do desmosomes involve? How do they work/
Involves a family of cadherins known as desmoglein and desmocollin.
These cadherins link to the intermediate filament cytoskeleton intracellularly and with each other extracellularly.
What do tight junctions do? (4 things)
- form a barrier between fluid compartments
- ensure any molecules moving across the epithelial cell layer must move through the cell, not between cells
- separate apical and basal domains of the plasma membrane
- prevent lateral movement of integral membrane proteins between the domains of the cell
What is a junction complex?
A region of cell-cell contact containing a tight junction, an adherens junction, and a desmosome.
What are gap junctions important for/
Cell-cell communication and coordination of cellular activity
What is the structure of a gap junction?
An open channel, called a connexon, through the plasma membrane that provide direct connections between the cytoplasm of adjacent cells
What do gap junctions allow for? What do they provide?
Allow for open flow of ions and other small molecules.
Provide a mechanism to couple metabolic and electrical activity of adjacent cells.
What is connexin?
A protein that forms gap junctions
