Lecture 5 Flashcards
Basal Lamina: produced by
Epithelium
Reticular lamina produced by
Connective tissue
Basement Membrane Characteristics
- Separates
- Thickness
- Components
- Separates epithelial cells from connective tissue support
- 50-80nm thick
- Basal lamina and reticular lamina
Components of the Basal Lamina
- Five components
- Laminin, Fibronectin, Type IV collagen, Enactin, proteoglycans
Components of the Basal Lamina
Type IV collagen Vs. Type I collagen: structural differences and how is each produced?
Type IV collagen does not form fibrils like type I collagen.
Type IV collagen is produced by epithelial cells. Type I collagen is secreted by fibroblasts.
Components of the Basal Lamina: Laminin
- What is special about it?
- Three chains?
- Binds with what?
- Major component of the basal lamina
- Alpha, beta, gamma
- Binds integrins, type IV collagen, enactin, and proteoglycans (heparan sulfate)
For number 3, we don’t need to memorize them, we just need to know what they all have in common. Type IV collagen, enactin, and proteoglycans are all three components of the basal lamina. It makes sense that laminin would bind those three.
Components of the Basal Lamina: Fibronectin
- Structure
- Two forms
- Binding sites for
- Two polypeptide chains cross-linked by disulfide bonds
- Plasma and cellular
- Heparin (proteoglycan), integrins, collagen, fibrin
(again, what do these three have in common?)
Cell Adhesion Molecules (CAMs)
- Two groups and two examples for each group
- Calcium dependent (cadherins and selectins)
- Calcium independent (integrins and IGG superfamily)
Cell Adhesion Molecules: Cadherins
- Calcium dependent?
- Ligans recognized
- Stable types of junctions
- Major components in?
- Typical conformations
- Includes (three)
- Yes
- Other cadherins
- Occludens and Desmosomes
- Calcium-mediated adherens junctions
- Typically form cis and trans homophilic dimers
- E-cadherins found in epithelial tissues, N-cadherins found in nerve cells, P-cadherins found in the placenta.
Cell Adhesion Molecules: Nonclassical Cadherins
- Two examples
- Found where
- Desmocollins and desmogleins
- Found in desmosomes (macula adherens)
Cell Adhesion Molecules: E-Cadherins
- What is special about this type of Cadherins?
- Structure and role of Ca ions in it
- What causes loss of these?
- Most common type of Cadherins
- Forms dimers via a HVA binding face at the top of the molecule. Calcium ions bind to the extracellular domains and facilitate cis-homophilic dimers.
- Invasive behavior of tumor cells.
Cell Adhesion Molecules: Catenins (will be on test)
- What do these do?
- Three forms and what they do.
- In general, what do these do?
- Small proteins that link the cytoplasmic end of a cadherin with cytoplasmic actin
- Beta and gamma: attached to cytoplasmic end of a cadherin. Beta may also be a tx cofactor. Betal is also attached to alpha catenin. Alpha: binds directly to cytoplasmic actin
- Catenins serve as a major interface between the cadherins that hold adjacent cells together and the actin cytoskeletons of those cells.
Cell Adhesion Molecules: Selectins
- Calcium dependent?
- Ligans regognized
- Stable types of Junctions
- What group to they belong to? Why?
- CRD Domain
- Involved in what?
- Yes
- Carbohydrates
- None
- Lectins because they bind carbohydrates
- Carbohydrate recognition domain aka binding site. Ca is required for this site to work (this is why the molecule is calcium dependent)
- movement of leukocytes from blood to tissues aka extravasation
Cell Adhesion Molecules: Classes of Selectins
- P-selectins
- E-selectins
- L-selectins
- Overarching theme here
- Associated with platelets
- Associated with activated endothelial cells. Endothelial cells are epithelial cells that line the blood vessels
- Associated with Leukocytes
- All of these are involved with blood stuff!
Cell Adhesion Molecules: Integrins
- Ca dependent?
- Ligands recognized
- Stable types of junctions
- What type of protein?
- In english, what do they bind to?
- Subunits: main point?
- In general what will you associate this with?
- No
- ECM molecules
- Hemidesmosomes
- Glycoprotein
- Molecules in the ECM and to the cytoskeleton
- Two subunits with several different types. Means many different kinds of integrins
- ECM and cytoskeleton!