Block 1 082412 Cell Adhesion And The Ecm

Front 1

What are the 3 primary types of cell junctions?

Back 1

1. Occluding/tight junctions
2. anchoring junctions
3. communicating / gap junctions

Front 2

What are the proteins that compose tight junctions?

Back 2

Claudins and Occludins

Front 3

What is the function of tight junctions?

Back 3

Tight/occludin junctions dictate permeablility and create membrane gradients

Front 4

What is the function and structure of anchoring junctions?

Back 4

Anchoring junctions connect the cytoskeleton of one cell to adjacent cells or the EMC to generate force. The structure consists of:
1. cytoskeletal filaments
2. anchoring proteins
3. transmembrane receptors

Front 5

Describe the difference between the two types anchoring junctions.

Back 5

1. Cell-cell interations:
-cytosketeton = actin filaments
-anchoring protein
-transmembrane receptor = cadherin dimers
2. Cell-ECM interactions:
-cytoskeleton
-anchoring protein= filamin, talin, alpha-actinin
-transmembrane receptor=Integrins (heterodimes of 1 alpha and 1 beta subunit

Front 6

What are two types of Cadherin anchoring junctions?

Back 6

1. Adherens junctions
2. desmosomes

Front 7

What are two types of Integrin anchoring junctions?

Back 7

1. Hemidesmosomes
2. Focal adhesions

Front 8

Describe the function and structure of adheren junctions.

Back 8

Adheren junctions lie below tight junctions in epithelia. Actin cytoskeleton filaments attach to anchoring proteins which attach to cadherin transmembrane receptor proteins. Whole thing called an adhesion belt. Cell movement create forces that allow entire sheets of cells to contract ex) in development, the invagination of epithelial sheets

Front 9

Describe the function and structure of desmosomes.

Back 9

Act like "buttons" so more structural. The cytoskeletal filaments intermediate filaments attach to anchoring proteins which attach to the transmembrane receptor cadherin

Front 10

Describe the function and structure of hemidesmosomes.

Back 10

They attach cells to part of the ECM called the basal lamina. Since it is more structural, the cytoskeletal component intermediate filaments attach to anchoring proteins which attach to the transmembrane receptor protein integrin

Front 11

Mutations in what cell junction can lead to severe blistering disorders?

Back 11

Mutations in the hemidesmosomes which are part of the integrin family of anchoring proteins, can cause blisters because it disrupts the attachment of epithelial cells to the ECM

Front 12

Describe the structure and function of focal adhesions.

Back 12

Focal adhesions are a type of anchoring junction that is very important in cell movement ex) muscle to tendon connections. The structure involves the cytoskeletal filament actin which attaches to anchor proteins which attach to the transmembrane receptor integrin

Front 13

What is the structure and function of gap junctions?

Back 13

There are tunnels connecting cells that allow for chemical and electrical signals to pass from cell to cell. These channels are formed by connexin proteins

Front 14

What type of molecules can pass through the connectins channels of gap junctions?

Back 14

small molecules like ions, sugars, AAs, nucleotides, vitamins, and intracellular mediators (cAMP). NOT macromolecules like proteins, polysaccharides or nucleic acids

Front 15

Before cell-cell junctions can form, what must take place?

Back 15

Cell-cell adhesions, which can be homophilic binding (2 of the same receptors on cells) heterophilic binding (cells with different receptors) or binding through an extracellular linker molecule

Front 16

What are the different classes of adhesion molecules?

Back 16

1. caherins: Ca++ dependent, involved in cell-sorting
2. Ig family: Ca++ independent
3. selectins: mediator s of cell-cell adhesion in the pbl stream, Ca++ dependent
4. integrins

Front 17

What two types of cell adhesion proteins would participate in white blood cells finding the site of injury from the blood through the endothelium?

Back 17

Wek adhesion and rolling actions would contribute to selectin proteins trying to find the site of injury while the strong adhesion and emigration actions would involve integrins

Front 18

What are the 2 primary types of ECM?

Back 18

1. Connective tissue/interstitium made of fibrillar collagens
2. Basal lamina

Front 19

What is connective tissue made primarily of?

Back 19

It is made of fibrillar collagens, the most abundant being collagen I

Front 20

What cell type makes collagen?

Back 20

Fibroblasts secrete procollagen I which is processed to collagen I

Front 21

What are the primary ECM proteins that compose each type of matrix

Back 21

Proteoglycans and glycosaminoglycans are prevalent in CT which are highly electronegative so they hold alot of water

Front 22

What are the 4 main types of glycosaminoglycans?

Back 22

1. Hyaluronic Acid (only one without a protein core or sulfation and spun on cell surfaces)
2. Chondroitin/dermatan sulfates
3.heparan sulfates
4. Keratan sulfates

Front 23

What is the basal lamina made of?

Back 23

1. Collagen IV: trimer that forms basket weave
2. Laminin: closest proximity of cell surface, trimer that forms cross
3. Nidogen: proteoglycans that connect the collagen to laminin
4. Perlecan: proteoglycans that connect the collagen to laminin