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

Cell-Cell contacting and signalling Flashcards

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
3- function
very close - fluid cannot pass seal but through transmembrane protein produces impermeable bonds between cells - limits paracellular permeability
26
3- limiting paracellular permeability
maintain osmotic variance across epithelial | e.g in gut or kidney
27
3- structure
claudin and occludin form bands at apes of epithelial | act as signalling centre
28
3- signalling centre of junction
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
3- polarised membrane
different molecules in different areas of membrane | not about charge
30
3- example of polarised membrane
apical - upper | basolateral - lower
31
3- failure of tight junction
AI diseases chronic inflammation IBD therefore important in innate immunity - oedema, diarrhoea and blood borne metastasis
32
3- cluster signalling molecules
claudin--claudin | occludin--occludin
33
2
anchoring junction
34
2- two forms
adherence junction | desmosomes
35
2- adherence junction
actin cytoskeleton - indirectly interacting with actins on neighbouring cells
36
2- desmosomes
intermediate filaments such as keratin - interact indirectly as well
37
2- cadherin
linking both forms and molecules between cell membrane | Ca2+ dependent adherence junction
38
2- cadherin structure
most have 5 cadherin-repeats and has Ca2+ binding sites between them have intracellular domain when adding Ca2+ causing CC in extracellular region
39
2- increase in Ca2+
dimer comes together = rigid and open binding region therefore interact with neighbouring cadherin - around 1mM Ca2+
40
2- classical cadherin
E, N, P, Ve cadherin | adherence junction
41
2- Atypical cadherin
in desmosomes - desmoglein, desmocollin
42
2- example for junction - embryo
remove Ca2+ - lose adherence = lose tight junction therefore cell becomes loose tight occurs if adherence occur
43
2- in classical
F-actin comes in on adapter protein + cadherin (exterior) = adherence junction = circumferential belt
44
2- in non-classical
keratin come in on adaptor + cadherin (exterior)
45
2- anchoring junction function
act as signalling centres - kinase and substrate | e.g. PI3 kinase
46
2- Wnt pathway
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
2- role - cell sorting 1
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
2 - role - cell sorting 2 - N and E-cadherin
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
2- failure to close tube
spina bifida - encephaloceles, hydranencephaly, iniencephaly in the brain - anencephaly - no brain formation
50
non-specialised cells
Notch and delta | Selectins
51
regulatory steps of notch and delta | cell 1 -
notch ligand expresser - has the delta ligand
52
regulatory steps of notch and delta | cell 2 -
notch receptor - larger area on outer surface of Golgi lumen
53
regulatory steps of notch and delta 1
notch receptor was cleaved by protease | notch remains to other part by non-covalent interaction at cell membrane and meets delta ligand
54
regulatory steps of notch and delta 2 meeting delta ligand
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
CC
conformational change
56
TACE
extracellular membrane bound enzyme
57
cell 1 function
stop proliferation at receptor in basal cell
58
regulatory steps of notch and delta 3 - in nucleus
binds to transcription machinery | receptor tail - bind to protein - converts it from repressor to activator transcription
59
notch pathway
regulating gene expression - turned on
60
turning off notch pathway
cells carry on differentiating and cells divides - (-/-) | hyperproliferation and tumour form
61
notch expression at skin epidermis
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
Selectins
lectins - sugar binding proteins
63
what produces selectins
by veil endothelial cell during inflammation by cytokines | placed on the surface of cell membrane
64
selectin function
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
P-selectin glycoprotein ligand 1
mucin type glycoprotein in all WBC
66
E selectin
activated endothelial
67
P selectin
activated endothelial and platelets | often in veins not arteries
68
basal cells
induced signal but not respond | also has melanocytes
69
regulatory of notch and delta in Golgi
cleave off ad transport to plasma membrane

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

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