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Genetics of cell growth and division > mitochondrial dynamics > Flashcards

mitochondrial dynamics Flashcards

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Biology 101 flashcards
1
Q

what can enlarged mt indicate?

A

disease

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2
Q

why are mt dynamics important for cell survival?

A
  • allows localisation to oxygen rich areas of the cell
  • redistribution of mt for cell division
  • mt cant be made, have to be inherited
  • important for accommodating cell growth
  • long tubular network more efficient for ATP generation so can generate ATP in oxygen poor areas of the cell
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3
Q

what are mitofusins involved in?

A

OMM fusion

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4
Q

what dynamin proteins are involved in IMM fusion?

A

Opa1/Mgm1

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5
Q

what dynamin proteins are involved in fission?

A

Drp1/dnm1

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6
Q

what experiments allowed to conclusion that mitofusins are essential for fusion?

A

ts mutant screens of fzo1 in yeast. male flies that lacked fzo couldn’t under fusion so were sterile.

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7
Q

what mammalian mitofusin is essential?

A

mfn1 and 2

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8
Q

phenotype of mice lacking mfns?

A

cells have fragmented mt, die due to placental defects

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9
Q

what disease is associated with mfn2 mutations?

A

charot marie tooth type 2a

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10
Q

what is the conserved structure of mfns?

A

4 heptad repeats, 1 GTPase domain and 2 transmembrane domains

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11
Q

phenotype at restrictive temp for ts mgm1 mutants?

A

decrease in mt fusion and more deformed mt

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12
Q

what mediates cell death?

A

decrease in short or long isoforms of post transcriptionally alternatively spliced opa1

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13
Q

what else is opa1 involved in?

A

maintance of cristae structure

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14
Q

what is MOM permebalision regulated by?

A

abundance of various apoptotic and anti-apoptotic proteins eg BCL-2

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15
Q

what changes causes apoptosis?

A

downregulation of fis1 and drp1 enhances fusion so inhibits apoptosis

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16
Q

key steps in mt fusion

A

1 docking and tethering by mitofusins
2 GTP hydrolysis to fuse OMM
3 tethering and fusion of IMM via mgm1 and opa1

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17
Q

what do mutations in fission proteins cause?

A

large nets of mt

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18
Q

dnm1/drp1 dimerise with other copies of the protein and form a curved structure, what do they do?

A

they pinch off mt using energy from GTP hydrolysis

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19
Q

what does dnm1 deletion cause?

A

networks of mt- unopposed fusion

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20
Q

what does a fzo1 mutation cause?

A

unopposed fission- results in punctate mt

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21
Q

what are the key steps in mt fission?

A

1 fis1 recruits drp1
2 oiligomerisation of multiple drp1 molecules to form a scission machinery
3. GTP hydrolysis fuels membrane scission

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22
Q

how may regulation of fusion/ fission occur?

A

protein stability, protein cleavage, protein conformation via binding of other proteins, phosphorylation, localisation via association with binding partners

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23
Q

what mechanisms regulate fission proteins?

A

drp1 regulated by phosphorylation, or by ubiquitination or through action of PKC/cyclin B/ PKA

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24
Q

what mechanisms regulate fusion proteins?

A

proteolysis, fzo1 degraded by ubiquitination, mgm1/opa1 undergoes proteolytic cleavage

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25
Q

what triggers mitophagy?

A

changes in mt membrane potential

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26
Q

steps in mitophagy

A

damaged/defective mt tagged with specific kinases and ubiquitin ligases (PARKIN), mt fusion disabled, mt destroyed by proteasome

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27
Q

why is mitophagy important?

A

allows defective mt to be removed

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28
Q

morphology of aging cells

A

large mt, low ATP production, loss of cristae structure due to loss of mt dynamics and impaired autophagy

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29
Q

what is a prerequisite to mitophagy?

A

fragmentation

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30
Q

what happens to nucleoids if fission decreases?

A

nuceloids cluster together and lose even distribution throughout the network

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31
Q

where are lots of nuceloids localised to?

A

fission sites- dont know if nucleoids dictate fission sites or nucleoids move to sites

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32
Q

what is ERMES?

A

ER-mitochondria encounter structure complex associates with mt fission sites and is present at 60% of division sites

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33
Q

mutation rate in mtDNA

A

10% higher than in nucelar, can be up to 50%- vicious cycle

34
Q

why are mtDNA mutations so frequent?

A

close proximity to ROS generation site

35
Q

what does defects in fission/ fusion machinery result in?

A

reduced mtDNA content, increased rate of mtDNA mutation

36
Q

what happens if you form a heteroplasmic cybrid from mutants?

A

can get complementation to restore oxphos activity

37
Q

how can you repair mtDNA mutations?

A

use WT genome to complement the mutant DNA

38
Q

what is the morphology of mt during G1/S phase?

A

more fusion and elongation of network for efficientm ATP production

39
Q

morphology of mt during mitosis?

A

more fission to distribute the mt to daughter cells

40
Q

morphology during interphase

A

tubular then fragment after

41
Q

what is essential for fission in mitosis?

A

phosphorylation of S585 of Drp1 by ckd1/cyclin BMPF

42
Q

what do mt move along?

A

actin cables

43
Q

name for movement towards mother

A

retrograde transport

44
Q

name for movement towards bud

A

anterograde

45
Q

where to more motile, fitter mt go?

A

to the bud

46
Q

what to mt in their bud have

A

fewer ROS

47
Q

during cell division what happens to mt

A

they are anchored at one of the poles

48
Q

what happens to PINK1 in healthy mt?

A

internalised and degraded

49
Q

what is PINK1

A

a serine threonine kinase

50
Q

what happens to PINK1 in defective kinases?

A

remains on surface and recruits PARKIN, this ubiquitinates mt proteins and is destroyed by mitophagy

51
Q

what is PARKIn

A

an E3 ubiquitin ligase

52
Q

how does fusion repair low functioning mt?

A

by intra organellar complementation

53
Q

what binds to unfolded proteins to stabilise them

A

chaperones

54
Q

what degrades damaged mt proteins

A

proteases

55
Q

what happens when there is too much fission?

A

compromised mtDNA integrity and biogenesis. results in ETC issues and decreased membrane potential

56
Q

what happens when there is too much fusion?

A

get englarged mt, decrease in mitophagy and biogenesis resulting in accumulation of damaged mt and increased oxidative stress. ETC issues and decreased membrane potential

57
Q

what decreases with age?

A

biogenesis capacity and autophagy

58
Q

what mediates biogenesis?

A

PGC1-alpha, stimulates TF activity and Mfn2 expression.

59
Q

what do T2DM and obese people have?

A

decreased mfn2 and PGC1alpha levels

60
Q

what does mutant Htt in HD cause?

A

abnormal calcium signallingand mt membrane potential. may colocalise with drp1 at fission sites and affect fusion and fission

61
Q

pathogenesity of PD?

A

degeneration of dopaminergic neurons in substantia niagra. decreased complex I activity there.

62
Q

how is mt involved in parkinsons

A

oxidative stress, mt dynamics and decreased mitophagy. mutations in PARKIN, PINK1 and mtDNA. mt cant keep itself healthy so results in decreased oxphos activity

63
Q

symptoms of autosomal dominant optic atrophy

A

ataxia, deafness, degradation of optic nerve

64
Q

how are mt involved in DOA

A

mtDNA depletion, Opa1 mutations, decreased oxphos- affects complex I

65
Q

what is involved in CMT2A- peripheral heriditary neuropathy

A

mfn2 mutations, mainly in the GTPase domain. defects in mt motility. decreased oxphos and mtDNA depletion

66
Q

older yeast have higher levels of what protein?

A

drp1

67
Q

what morphology to older cells tend to have?

A

fragmented

68
Q

what can not occur in absence of opa1?

A

inner membrane fusion, but outer membrane fusion still occurs

69
Q

what does DOA alleles disrupt?

A

opa1 function, resulting in fragmented mt and loss of fusion activity

70
Q

what happens in zebrafish that lack mfn2?

A

fusion failure. leads to adult onset motor dysfunction like CMT2A. progressive motor defects in swimming and altered mt distribution along axons due to defects in retrograde transport

71
Q

why is the mt abnormally distributes in cmt2a patients?

A

defects in retrograde transport

72
Q

what does overexpression of PINK1 cause in dopmine neurons?

A

induced mt clustering due to excessive fission

73
Q

what is the epistatic order of the pathway controlling mt fission?

A

pink1, fis1, drp1

74
Q

PINK1 interacts with what protein?

A

drp1, maybe other fission/ fusion proteins eg drp1

75
Q

what do HD patients have higher and lower levels of?

A

higher levels of fission proteins drp1, fis1 and CypD. lower levels of mfn1,mfn2 and opa1

76
Q

how may mutant htt cause damage?

A

generate oxidative conditions

77
Q

what activity is decreased in HD patients?

A

cox1 and cytb

78
Q

deletion of dnm1 results in what?

A

increased replicative lifespan and increased resistance to apoptosis

79
Q

deletion of mgm1 does what?

A

decreases replicative lifespan- no fusion, decreased mitophagy

80
Q

simultaneous impairment of both fission and fusion proteins does what?

A

cause mtDNA instability

Genetics of cell growth and division (9 decks)

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