Epithelium: Cell Junctions Flashcards

1
Q

Name the asymmetric junction(s)

A

Hemidesmosome (attach cells to the basal lamina)

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2
Q

Name the symmetric junction(s)

A

(btwn two cells) Tight Junction (occluding junction) Anchoring Junction ( belt desmosomes) Anchoring Junction ( spot desmosomes) Communicating Junction (Gap)

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3
Q

Tight Junction (occluding)

A

No intercellular space -circumferential belts at the apical domain of epthelial cells -links adjacent endothelial cells -regulate the passage of ions between adjacent epithelial cells -

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4
Q

Transcellular Pathway

A

Across the cell controlled by channels and receptors

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5
Q

Paracellular Pathway

A

Between the cells regulated by intracellular contact and CELL JUNCTIONS

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6
Q

Actin filaments are seen in what type of Junction

A

Tight

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7
Q

What is anchored to Zo-1 in Tight Junctions

A

Afadin-nectin complex JAMS

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8
Q

What type of dimers do Nectins form

A

cis-homodimers transhomodimers

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9
Q

JAMS (Junctional adhesion molecules) attach to

A

afadin and ZO-1

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10
Q

JAMS determine…

A

formation of cell polarity

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11
Q

Order of Junctions from the Lumen down

A

Tight (occluding) Zonula adherens (belt) Macula adherens (spot)

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12
Q

Tight Junctions ..what interacts with F-actin

A

occludin claudins JAMS

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13
Q

What components of the tight junction are seen in freeze fracture?

A

Occludin and Claudins

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14
Q

What type of junctions are show from top to bottom

Line 1

Line 2

Line 3

A

Tight Junction

Zonula adherens

Macula adherens

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15
Q

What type of Junction is this?

A

Tight Junction (freeze fracture) occludin and claudins

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16
Q

What type of Junction is #2

What is inside this intercellular space ?

A

Tight Junction

Occludin

Claudins

JAMS

Nectins

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17
Q

What type of Tight Junctions are part of the immunoglobin family of Cell Adhesion Moleculess?

A

Nectin and JAMS

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18
Q

Occludin and Claudin are part of what family of proteins?

A

Tetraspanins

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19
Q

What part of Tight Junctions are actin Linkers?

A

ZO

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20
Q

Tight Junctions separate which two domains?

A

Apical and Basolateral membrane domains

(prevent free diffusion of lipids and membrane proteins between them)

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21
Q

Tight Junctions regulate …

A

Paracellular Pathway of fluid and solutes (kidney blood filtration)

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22
Q

Nectin and JAMS form homodimers through what bonds

A

disulfide bonds

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23
Q

What type of filaments are associated with tight junctions?

A

Actin (microfilaments)

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24
Q

Freeze Fracture

A

Creates artifical (FACE)

Protoplasmic (wear bumps are seen) where occuludin and claudins seen

Extracellular face (where pits are seen)

results from spitting membrane across hydrophic core

uses heavy metals to coat the cell

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25
Q

Occludin is attached to what ZO

A

ZO2

26
Q

Clauddin is attached to

A

ZO 4

27
Q

Belt desmosome

Zonula adherens

A

Afadin-nectin complex

plaques (desmoplakin, plakoglobin (gamma catenin), plakophillin) *anchor*

catenin ( alpha, beta, gamma) go wit cadherins connect to actin

cadherins ( desmocollins and desmogleins)

28
Q

What is seen in both tight junctions and belt desmosomes?

A

Afadin-nectin complex

29
Q

Plaques ( belt desmosomes)

A

Anchor

where cytoplasmic domains of cadherins attach to desmoplakin by plakglobin and plakophillin

30
Q

Belt Desmosomes

A

belt like

actin filaments (interaction of cadherins with catenins)

wide extracellular space

31
Q

Belt

Cadherins

A

atttaches to cytoplasmic plaques on cystolicface of plasma membrane

  1. desmocollins
  2. desmogleins (1 &3 are in epidermis, if issue the pemphigus foliacus)
32
Q

Pemphigus Foliacus

A

Blistering Disease

issue with Desmogleins 1 & 3 (affects epidermis)

33
Q

What are the types of juntions seen?

A

Top is Tight Junction

Bottom is belt desmosome ( can tell because of hte actin filaments but the extracellular space is further apart then the tight )

34
Q

What are the anchoring desmosomes?

A

Spot

Belt

Hemidesmosome

35
Q

Name a communicating Junction?

A

Gap

36
Q

Name an occluding Junction?

A

Tight

37
Q

Spot desmosome

macula adherens

A

Keratin/ tonomfilaments/ intermediate filaments

Plaques ( plakoglobin, plakophillin, desmoplakin)

Cadherins (desmocollins and desmogleins)

add strenth and rigidty to epithelium layer

38
Q

What is anchored to desmoplakin in spot desmosomes?

A

Intermediate filaments

39
Q

Differences between belt desmosome and spot desmosome?

A

spot desmosome has

intermeidate filaments (anchor directly to plaque)

and no catenins

40
Q

What type of desmosomes are seen in intercalated discs?

A

spot desmosomes

41
Q

Role of Plakophillin

A

In plaues (spot and belt desmosomes)

recruit protiens to the plasma membranes

42
Q

Disorder with Desmoglein (cadherin)

A

striate palmoplantar keratoderma (hypotrichosis)

43
Q

Issue with desmoplakin (plaque)

A

ARVC, woolyhair

44
Q

Issue with Plakoglobin

A

Naxos Disease

ARVC, wooly hair

palmoplantar keratoderma

45
Q

In this picture of a spot desmosome what is the top line pointing to?

A

intermediate filaments

46
Q

Bullous Phemphigoid

A

autoimmune disease of the skin

BLISTER

deals with hemidesmosomes

Antibodies to BPAG1 or BPAG2 results in detachment of hemidesmosome fromt he basal lamina

47
Q

Hemidesmosomes

A

Asymetric

BPAG1 and BPAG2

Integrins (beta 4 alpha 6) +pectin

Laminin 5

Intermediate filaments (anchored to the plaque) (inner cytoplasmic plate)

Plaque (DIFFERENT TYPE-NO DESMOPLAKIN, NO PLAKOPHILLIN AND NO PLAKOGLOBIN)

Inner cytoplasmic plate (IF)

outer cytoplasmic plate ( link hemidesmosome to basal lamina with lamisn and integrin)

aids with stability

48
Q

Gap Junctions

(communicating junctions)

A

Link adjacent cells

Connexon: formed by 6 connexins surrounding a central channel

Inner channel: allows direct passage of small signaling molecules (calicum and camp) between adjacent cells (helps with coordinating cell responses)

hyrophiliic inner channel

49
Q

What junctions tend to have a clustering tendancy?

A

Gap junctions

50
Q

What junctions are seen in heart muscle cells?

A

Gap Junctions

conduct electricity

51
Q

Issue with Connexin 26

A

cochlea (deafness)

52
Q

Issue with conexin 32

A

charcot marie tooth demyelinating neuropathay 1

X linked

issue with Schawn Cells

53
Q

Connexin 50

A

cataracts (blindness)

54
Q

Connexin 43 and 45

A

Bone cells

osteoclast/osteoblast

skeletal defects

55
Q

Role of Basement membrane

A

supporting sheet epithelia

56
Q

Integrins mediate

A

cell-matrix interaction

because of binding affinty to RGD domain in laminin and fibronectin (which are proteins of ECM)

57
Q

Basal Lamina

A

laminin

iv collagen

entactin (nidogen)

proteoglycans (heparn sulfate)

58
Q

Reticlar Lamina

A

collagen fibers (III)

supports basal lamina with connective tissue

59
Q

Things that are PAS POS

A

collagens

mucus (goblet)

glycocalyx

glycoproteins (pituitary gland)

basement membrane

60
Q

Laminin

A

basal lamina

3 disuflfide linked polypeptide chains (alpha beta gamma)

binding sites for cells surface receptors (integrins), type IV collagen, nidogen

61
Q

Fibronectin

A

glycoprotein

two identical chains joined by disulfide linkage close to C terminal

Two types

Cellular -produced by fibroblas (ECM)

Plasma- produced by hepatocyes (bloodstream)

62
Q
A