Extracellular Matrix and Adhesion

Question 1

Functions of ECM (6)

Answer 1

Scaffolding
Regulates Cell Survival (Integrins)
Differentiation
Migration (GAGs)
Proliferation
Shape

Question 2

Four major components of ECM

Answer 2

Glucosaminoglycans
Proteoglycans
Fibrous Proteins: Collagen and Elastin
Multidomain Adaptor proteins: Fibronectin & Laminin

Question 3

Glucosaminoglycans

Answer 3

repeated disaccharides that can attach to serine residues through a tetrasaccharide linker.
Acetylation/Sulfation determines type of GAG
Cross-linking helps with ECM structure
Can bind signals (usually inactive when bound) such as selectins for leukocyte extravasation

Question 4

Collagen

Answer 4

Most abundant protein in body, main ECM component
Different collagens have different properties
Coiled trimer = pro-collagen, termini removed = tropo collagen
Provide scaffolding

Question 5

Fibronetin/Laminin

Answer 5

Signaling molecules in ECM, multimers that change ECM properties
Fibronectin: dimer formed by C terminus disulphide bridge. Self association and collagen, cell, and heparin binding domains to maximize cross linking
Laminin: Heterotetramer w/ multiple cross-linking chains/domains

Question 6

MMPs

Answer 6

Actin protrusions at leading edge coupled with myosin provides movement.
MMPs are zinc-dependent, inactive w/ C terminus attached. Secreted into ECM where C terminus is cleaved and they degrade ECM and activate signals associated with GAGs

Question 7

Adhesion and Cell Survival

Answer 7

Cells require binding to ECM via integrins in order to survive.

Question 8

Integrins

Answer 8

transmembrane heterodimers of alpha and beta subunits that recognize specific ECM proteins
Beta unit binds actin intracellularly via adaptor proteins, important in cell motility.
Promote survival and suppress apoptosis when bound to ECM, opposite when not bound to ECM

Question 9

Cadherins

Answer 9

calcium dependent homodimers that create junctions between cells.
Bind actin intracellularly via beta catenin

Question 10

CAMs and signaling

Answer 10

Rho associated with CAMs, Beta catenin with cadherins