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BIOL1025 - Fundamentals of cell biology and physiology > Cell-Cell contacting and signalling > Flashcards

Cell-Cell contacting and signalling Flashcards

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1
Q

complexes

A

forms at cell surface for interaction site and signalling centre
specialised contact

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2
Q

example of complexes

A

anchoring, tight and gap junction

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3
Q

anchoring junction

A

adherence junction and desmosome

induced by cadherins

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4
Q

tight junction

A

include claudins together and occludins on membrane

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5
Q

gap junction

A

intimate fusion by connexins

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6
Q

notch-delta

A

don’t occur at any specific complex

non-specialised such as selectins as well

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7
Q

organisation of junctions - starting from bottom

A
  1. communication junction
  2. anchoring junction
  3. occluding junction
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8
Q
  1. communicating junction
A

gap- allows communication between cells
primary importance
in plants - Plasmodesmata

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9
Q
  1. anchoring
A

stabilise epithelial sheet and cell next to each other
act as linkage
adherence - actin attachment site
desmosomes - intermediate filament attachment site

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10
Q
  1. occluding
A

tight(vertebrate) and septate(invertebrate) junctions
occlude movement of fluid and anything in fluid
act as block

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11
Q

heterophilic

A

different protein from signalling and target

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12
Q

1

A

communicating junction

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13
Q

1 - functional syncytia

A

membrane intact with small canals which allow small molecules in and out

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14
Q

1- full syncytia

A

some membrane break down completely

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15
Q

1- pores in membrane

A

align to next membrane
regulated by electro-chemical coupling of cells
common in excitable cells

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16
Q

1- example of excitable cells

A

cardiac muscles cells

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17
Q

1- junctions characteristic

A

very strong as ions can transfer from gap junction when excited

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18
Q

1- how gap junctions are formed

A
  • 6 connexins get together to form pore likes structure
  • with another 6 connexins = 2 connexons
  • has charge in opening - limiting size of molecules and ions able to pass through 2nm apart
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19
Q

1- types of connexins

A

14 different types = mix and match

form connexons - heteromeric or homomeric

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20
Q

1- different gap junction formation

A

some sit individually
some brought together to form large structure = gap junction complex
very cell type dependent

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21
Q

1- example of gap junction regulation - light

A

Retina - high [Ca2+] channels close - stimulated by light
+ dopamine or mimics dark - gap junctions open
- dopamine of mimics bright light - closes

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22
Q

1- apoptosis

A

intracellular levels of [Ca2+] increases = junction closes

stops spreading of signals of cell death to other cells

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23
Q

1- example of gap junction complex

A

intercalated disc of heart

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24
Q

3

A

tight junction

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25
Q

3- function

A

very close - fluid cannot pass seal but through transmembrane protein
produces impermeable bonds between cells - limits paracellular permeability

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26
Q

3- limiting paracellular permeability

A

maintain osmotic variance across epithelial

e.g in gut or kidney

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27
Q

3- structure

A

claudin and occludin form bands at apes of epithelial

act as signalling centre

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28
Q

3- signalling centre of junction

A

pKa - regulate signalling cascade and G coupling protein
at membrane concentrates at tight junctions
ZONAB - change in junction like damage - released and migrates to nucleus and act as transcription fact
regulation gene expression

29
Q

3- polarised membrane

A

different molecules in different areas of membrane

not about charge

30
Q

3- example of polarised membrane

A

apical - upper

basolateral - lower

31
Q

3- failure of tight junction

A

AI diseases
chronic inflammation
IBD
therefore important in innate immunity - oedema, diarrhoea and blood borne metastasis

32
Q

3- cluster signalling molecules

A

claudin–claudin

occludin–occludin

33
Q

2

A

anchoring junction

34
Q

2- two forms

A

adherence junction

desmosomes

35
Q

2- adherence junction

A

actin cytoskeleton - indirectly interacting with actins on neighbouring cells

36
Q

2- desmosomes

A

intermediate filaments such as keratin - interact indirectly as well

37
Q

2- cadherin

A

linking both forms and molecules between cell membrane

Ca2+ dependent adherence junction

38
Q

2- cadherin structure

A

most have 5 cadherin-repeats and has Ca2+ binding sites between them
have intracellular domain when adding Ca2+ causing CC in extracellular region

39
Q

2- increase in Ca2+

A

dimer comes together = rigid and open binding region therefore interact with neighbouring cadherin - around 1mM Ca2+

40
Q

2- classical cadherin

A

E, N, P, Ve cadherin

adherence junction

41
Q

2- Atypical cadherin

A

in desmosomes - desmoglein, desmocollin

42
Q

2- example for junction - embryo

A

remove Ca2+ - lose adherence = lose tight junction therefore cell becomes loose
tight occurs if adherence occur

43
Q

2- in classical

A

F-actin comes in on adapter protein + cadherin (exterior) = adherence junction = circumferential belt

44
Q

2- in non-classical

A

keratin come in on adaptor + cadherin (exterior)

45
Q

2- anchoring junction function

A

act as signalling centres - kinase and substrate

e.g. PI3 kinase

46
Q

2- Wnt pathway

A

reservoir of signalling molecules - alpha/beta- catenin
regulate cell division
when active - alpha/beta catenin released into cell nucleus = signal and drive cell division

47
Q

2- role - cell sorting 1

A

separating neuronal and epithelial - in vivo - in presence of N/E cadherin
centre express N-cadherin and rest on N and C terminus is E-cadherin

48
Q

2 - role - cell sorting 2 - N and E-cadherin

A

N-cadherin remain together - starts invaginating and fuse = epithelial tube of N-cadherin expressing cells
E-cadherin on outer surface - separated
= CNS - N-cadherin tube
= skin - E-cadherin tube

49
Q

2- failure to close tube

A

spina bifida - encephaloceles, hydranencephaly, iniencephaly
in the brain - anencephaly - no brain formation

50
Q

non-specialised cells

A

Notch and delta

Selectins

51
Q

regulatory steps of notch and delta

cell 1 -

A

notch ligand expresser - has the delta ligand

52
Q

regulatory steps of notch and delta

cell 2 -

A

notch receptor - larger area on outer surface of Golgi lumen

53
Q

regulatory steps of notch and delta 1

A

notch receptor was cleaved by protease

notch remains to other part by non-covalent interaction at cell membrane and meets delta ligand

54
Q

regulatory steps of notch and delta 2 meeting delta ligand

A

signal passed causing CC therefore notch cleaved from cells 2 by TACE
causing CC and another enzyme (y-secretase) at intercellular part of receptor - released and carried to nucleus

55
Q

CC

A

conformational change

56
Q

TACE

A

extracellular membrane bound enzyme

57
Q

cell 1 function

A

stop proliferation at receptor in basal cell

58
Q

regulatory steps of notch and delta 3 - in nucleus

A

binds to transcription machinery

receptor tail - bind to protein - converts it from repressor to activator transcription

59
Q

notch pathway

A

regulating gene expression - turned on

60
Q

turning off notch pathway

A

cells carry on differentiating and cells divides - (-/-)

hyperproliferation and tumour form

61
Q

notch expression at skin epidermis

A

1 - dividing cells - differentiates but not divide
2- differentiating - notch and receptor - induce and respond signalling - inhibit cell division and induce cell differentiation
3 - differentiated - no expression

62
Q

Selectins

A

lectins - sugar binding proteins

63
Q

what produces selectins

A

by veil endothelial cell during inflammation by cytokines

placed on the surface of cell membrane

64
Q

selectin function

A

bind to ligand on WBC - slows them down and migrate out of tissue
activating E and P expressed - 1 bind platelets which degranulates and E - carbohydrate on glycoprotein of WBC = rolling

65
Q

P-selectin glycoprotein ligand 1

A

mucin type glycoprotein in all WBC

66
Q

E selectin

A

activated endothelial

67
Q

P selectin

A

activated endothelial and platelets

often in veins not arteries

68
Q

basal cells

A

induced signal but not respond

also has melanocytes

69
Q

regulatory of notch and delta in Golgi

A

cleave off ad transport to plasma membrane

BIOL1025 - Fundamentals of cell biology and physiology (21 decks)

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