ILA Cell-cell Junctions (Sayner)

Question 1

occluding junctions

Answer 1

most apical
multiprotein junctional complexes
zonula occludens (tight junctions)

Question 2

anchoring junctions

Answer 2

zonula adherens (belt desmosomes)
macula adherens (spot desmosomes, beneath zonula adherens)

Question 3

communicating junctions

Answer 3

gap junctions

Question 4

Tight junctions

Answer 4

anastomosing network

limit paracellular transport and generate cell polarity

Question 5

paracellular transport

Answer 5

diffuse between cells

Question 6

transcellular transport

Answer 6

pass through cell

requires cell polarity and selective transport proteins

Question 7

transmembrane proteins of tight junctions

Answer 7

link together in extracellular domain

• claudins
• occludins
• junctional adhesion molecules (JAMS)

Question 8

Intracellular tight junction proteins

Answer 8

bind to transmembrane proteins and ACTIN

link cytoskeletal elements of adjacent cells

Question 9

Adherens junctions

Answer 9

form a belt

connect ACTIN filament bundles between cells

Question 10

desmosomes

Answer 10

spot attachments

connect INTERMEDIATE FILAMENTS between cells

important in skin

Question 11

anchoring junctions transmembrane adhesion molecules

Answer 11

• cadherins
  
  • homophilic
  • cell recognition
  • calcium dependent
  • weak interactions
• immunoglobulin superfamily
  
  • cell adhesion molecule (CAM)
  • calcium independent
  • inflammation and immune response
  • homophilic and heterophilic interactions
• selectins
  
  • bind sugars
  • expressed on WBCs and endothelial cells
  • heterophilic interactions
  • calcium dependent

Question 12

gap junctions

Answer 12

electrical and metabolic coupling between cells

6 connexin proteins → assemble to form connexon → spans lipid bilayer → align with connexons of adjacent cells to form a functional gap junction

Question 13

basement membrane

Answer 13

secreted by epithelial cells

collagen IV and laminin form sheets anchored by nidogen and perlecan

fibronectin forms attachment sites for cells into the basement membrane

Question 14

basement membrane functions

Answer 14

structural attachment and cell polarity

support

compartmentation

filtration

scaffold for tissue regeneration and migration

regulates signaling

Question 15

visualization of basement membrane

Answer 15

PAS stain

Question 16

degradation of basement membrane

Answer 16

Matrix metalloproteinases (MMPs)

TIMPS regulate (inhibit/slow down degradation)

Question 17

reticular lamina

Answer 17

type III collagen

Question 18

anchoring fibrils

Answer 18

Type VII collagen

Question 19

fibrillin microfibrils

Answer 19

attach the basal lamina to elastic fibers of connective tissue

Question 20

cell-matrix junctions

Answer 20

anchoring junctions: focal adhesions, hemidesmosomes

Question 21

cell-matrix junction transmembrane adhesion molecules

Answer 21

• integrins
  
  • extracellular domain binds laminin and fibronectin
  • heterophilic interactions
  • heterodimers
    
    • many different isoforms allow for functional specificity

Question 22

outside-in activation

Answer 22

binding of matrix proteins → intercellular conformational change of integrin to active → intra cellular binding domains altered

Question 23

inside-out activation

Answer 23

extracellular signals activate talin → talin activates integrin

Question 24

focal adhesions

Answer 24

link integrins into actin cytoskeleton

Question 25

hemidesmosomes

Answer 25

spot attachments on basal membrane

Function: increase adhesion for epithelial cells exposed to mechanical shearing forces

transmembrane proteins: extracellular domain binds laminin and collagen IV

anchoring proteins link into keratin intermediate fibers