Question

Cell Biology Tutorial: The Extracellular Matrix

Answer 1

This is a tutorial, not a question. As such, please save all commentary questions for the end. I will be handing out warnings and possibly suspensions for irrelevant spam comments.

Answer 2

\({\bf{The~Basics:}}\)

- Matrisome: the proteins that make up the ECM and any associated proteins involved in its structure and regulation
- Basal lamina supports/surrounds most cells

Components:
- laminin: links components of the basal lamina, has alpha, beta, and gamma chains
> LG domains that bind to receptors like integrins
- type IV collagens: forms structure of the basal lamina, alpha chains, may be helical
> glycine, proline, hydroxyproline --> Gly-X-Y
- perlecan: large protein core + polysaccharides w/ LG/Ig domains
> N-linked, O-linked, and GAGs (long chains of repeating disaccharides)
> GAG + glycoprotein = proteoglycan
> binds to other molecules like ECM and receptors --> cross-linking

\({\bf{Connective~Tissues:}}\)
Collagens, GAGs, proteoglycans, multi-adhesive proteins, elastin

Fibrillar Collagens: microfibrills --> fibrils -> fibers
other types: fibril-associated collagens, sheet forming and anchoring collagens, transmembrane collagens, host defense collagens
- produced by fibroblasts
- staggered distribution, causes striated patterns in microscopy

Type I: longer, "stretchier" , found in tendons, associated with type VI
type II: smaller in diameter, mesh-like, associated with type IX

\({\bf{Proteoglycans/GAGs:}}\)
- as a refresher proteglycans contain long sugar chains called GAGs
- GAGs have negative charges
- classified by the disaccharide (hyaluronan, chondroitin, heparin/heparan, keratan)
- O-linked: sugar linker attached to hydroxyl side chains of serine
- N-linked: sugar linker attached to asparagine

\({\bf{Syndecans:}}\) cell-surface proteoglycans, bind to collagens and adhesive proteins, or growth factors
\({\bf{Hyaluronan:}}\) a GAG that plays a role in migration/flexibility; associates w/ aggrecan in cartilage to make it more gel-like
\({\bf{Fibronectin:}}\) multi-adhesive matrix protein, binds to ECM components
-dimers of polypeptides
- type III binds with integrin, requires RBD domain
\({\bf{Elastin:}}\) makes up elastic fibers, allow reversible stretching of tissues, made of proline/glycine hydrophobic motifs which allow them to stretch