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Flashcards in Lecture 5 Deck (28):
1

Basal Lamina: produced by

Epithelium

2

Reticular lamina produced by

Connective tissue

3

Basement Membrane Characteristics

  1. Separates
  2. Thickness
  3. Components

  1. Separates epithelial cells from connective tissue support
  2. 50-80nm thick
  3. Basal lamina and reticular lamina

4

Components of the Basal Lamina

 

  1. Five components

  1. Laminin, Fibronectin, Type IV collagen, Enactin, proteoglycans

5

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.

6

Components of the Basal Lamina: Laminin

  1. What is special about it?
  2. Three chains?
    1. Binds with what?

  1. Major component of the basal lamina
  2. Alpha, beta, gamma
  3. 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.

7

Components of the Basal Lamina: Fibronectin

  1. Structure
  2. Two forms
  3. Binding sites for

  1. Two polypeptide chains cross-linked by disulfide bonds
  2. Plasma and cellular
  3. Heparin (proteoglycan), integrins, collagen, fibrin

 

(again, what do these three have in common?)

8

Cell Adhesion Molecules (CAMs)

  1. Two groups and two examples for each group

  1. Calcium dependent (cadherins and selectins)
  2. Calcium independent (integrins and IGG superfamily)

9

Cell Adhesion Molecules: Cadherins

  1. Calcium dependent?
  2. Ligans recognized
  3. Stable types of junctions
  4. Major components in?
  5. Typical conformations
  6. Includes (three)

 

  1. Yes
  2. Other cadherins
  3. Occludens and Desmosomes
  4. Calcium-mediated adherens junctions
  5. Typically form cis and trans homophilic dimers
  6. E-cadherins found in epithelial tissues, N-cadherins found in nerve cells, P-cadherins found in the placenta.

10

Cell Adhesion Molecules: Nonclassical Cadherins

  1. Two examples
  2. Found where

  1. Desmocollins and desmogleins
  2. Found in desmosomes (macula adherens)

11

Cell Adhesion Molecules: E-Cadherins

  1. What is special about this type of Cadherins?
  2. Structure and role of Ca ions in it
  3. What causes loss of these?

  1. Most common type of Cadherins
  2. 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.
  3. Invasive behavior of tumor cells.

12

Cell Adhesion Molecules: Catenins (will be on test)

  1. What do these do?
  2. Three forms and what they do.
  3. In general, what do these do?

  1. Small proteins that link the cytoplasmic end of a cadherin with cytoplasmic actin
  2. 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
  3. Catenins serve as a major interface between the cadherins that hold adjacent cells together and the actin cytoskeletons of those cells. 

13

Cell Adhesion Molecules: Selectins

  1. Calcium dependent?
  2. Ligans regognized
  3. Stable types of Junctions
  4. What group to they belong to? Why?
  5. CRD Domain
  6. Involved in what?

  1. Yes
  2. Carbohydrates
  3. None
  4. Lectins because they bind carbohydrates
  5. Carbohydrate recognition domain aka binding site. Ca is required for this site to work (this is why the molecule is calcium dependent)
  6. movement of leukocytes from blood to tissues aka extravasation

14

Cell Adhesion Molecules: Classes of Selectins

  1. P-selectins
  2. E-selectins
  3. L-selectins
  4. Overarching theme here

  1. Associated with platelets
  2. Associated with activated endothelial cells. Endothelial cells are epithelial cells that line the blood vessels
  3. Associated with Leukocytes
  4. All of these are involved with blood stuff!

15

Cell Adhesion Molecules: Integrins

  1. Ca dependent?
  2. Ligands recognized
  3. Stable types of junctions
  4. What type of protein?
  5. In english, what do they bind to?
  6. Subunits: main point?
  7. In general what will you associate this with?

  1. No
  2. ECM molecules
  3. Hemidesmosomes
  4. Glycoprotein
  5. Molecules in the ECM and to the cytoskeleton
  6. Two subunits with several different types. Means many different kinds of integrins
  7. ECM and cytoskeleton!

16

Cell Adhesion Molecules: Integrins Interactions

  1. Interacts with what sequence in which proteins?
  2. What do these proteins interact with?
  3. Function in hemidesmosomes?

  1. RGD sequence in fibronectin and laminin
  2. Fibronectin and laminin interact with collagen, heparan sulfate proteoglycans, and entactin
  3. link basal domains of cells to the ECM via intracellular filaments (like keratin)

17

Cell Adhesion Molecules: IGG Superfamily

  1. Calcium dependent?
  2. Ligands recognized?
  3. Stable types of Junctions?
  4. Characteristic structure
  5. N-CAM
  6. I-CAM-1 and I-CAM-2

  1. No
  2. Integrins
  3. None
  4. Extracellular segment with one or more folded domains
  5. neural adhesion molecules - mediate homophilic and heterophilic interactions
  6. Facilitates transendothelial migration of leukocytes

18

Junctional Complexes: Adherens

  1. Function
  2. Found
  3. Structure
  4. Cadherin proteins (2)
  5. Cadherin proteins anchored to

  1. Anchor cells together and reinforce physical integrity of tissues and the cells that make up the tissues.
  2. Basolateral surfaces of epithelial cells
  3. Filled with cadherin proteins
  4. Desmogleins 1 and 2 and desmocollins
  5. Cytoplasmic plaques containing desmoplakin and plakoglobin

19

Junctional Complexes: Occludens (Will be on the test)

  1. Function
  2. Result

  1. Establish an impermeable barrier between adjacent cells (especially epithelial cells).
  2. This prevents paracellular transport and maintains concentration differences.

20

Junctional Complexes

  1. Three types

  1. Adherens, Occludens, and Gap Junctions

21

Junctional Complexes: Gap Junctions

  1. Composed of?
  2. Enable?
  3. Purpose?

  1. Molecular pores
  2. rapid exchange of ions and small molecules
  3. Allows coordination of activities among cells making up a tissue

22

Junctional Complex Types: Zonula

  1. Which category of junctional complex can this be?
  2. What do these do?
  3. Associated with which molecule?

  1. Adherens or occludens
  2. Link all neighboring cells to central cell.
  3. Intracellular actin

23

Junctional Complex Types: Macula

  1. Which category of junctional complex can this be?
  2. AKA
  3. Which molecule are these associated with?
  4. Why wouldn't occludens have this type of junctional complex?

  1. Adherens
  2. Desmosomes (when associated with the lateral domains) or hemidesmosomes (when associated with the basal domain of epithelial cells
  3. Intracellular intermediate filaments. 
  4. They can be navigated around! They are not tight

24

Junctional Complexes: Adherens

  1. Zonula adherens associated with?
  2. Macula adherens associated with?
  3. Associates are mediated by interactions with...

  1. Microfilaments
  2. Intermediate filaments
  3. Cadherins: desmocollins and desmogleins

25

Junctional Complexes: Hemidesmosomes

  1. Function
  2. Consists of (2 things)

  1. Anchor basal domain o fthe epithelial cell to the basal lamina
  2. Cytoplasmic plate (associated with IF like Keratin) and membrane plaque (links molecule to basal lamina)

26

Junctional Complexes: Zonula Occludens

  1. What is it?
  2. Purpose
  3. Proteins?
  4. JAMS and Nectin

  1. Forms a tight junction. Occludes
  2. Provide barrier against paracellular transport pathway. So, prevents transport of fluids and solutes
  3. Claudins and Occludins. Attach intracellularly
  4. Members of IGG superfamily, stabilized by disfulfide bonds. 

27

Junctional Complexes: Focal Adhesions

  1. What are these?
  2. What protein do they use?
  3. How do they differ from desmosomes?
  4. Stability

  1. Spots that anchor the cell to the ECM
  2. Integrins
  3. Intracellular attachment is not to tonofilaments like keratin, but to actin filaments
  4. The extracellular portion can be unfolded and connected to ECM OR it can be folded in for cellular motility. 

28

Junctional Complexes: Gap Junctions

  1. What does this do?
  2. Composed of?
  3. Structure of the composition protein?
  4. When is it closed?
  5. What is it responsible for?

  1. Communication! Allows for cells to communicate
  2. Connexons
  3. 6 connexins form a hexagonal structure with hollow center. Often clustered into patches.
  4. When Ca ion concentrations are high (prevents Ca from entering)
  5. Chemical and electrical coupling

Note that connexon and connexin are different