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Metabolic Basis of Disease > Final & Midterm 1 > Flashcards

Final & Midterm 1 Flashcards

1
Q

mTOR

A

activated by leucine and growth factors (insulin), inhibited by AMPK, phosphorylates 4E-BP and S6K –> promotes protein synthesis

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2
Q

eIF2

A

When GTP bound, eIF2 mediates the formation of 43S pre initiation complex, if eIF2 is phosphorylated it will be trapped in inactive/GDP bound form - eIF2 acts as “brakes” to stop protein translation if anything goes wrong

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3
Q

“brakes” of protein translation

A

eIF2

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4
Q

PERK

A

phosphorylates eIF2 during ER stress

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5
Q

GCN2

A

phosphorylates eIF2 during nutrient limitation

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6
Q

eIF4F

A

complex that binds to cap of mRNA and drives protein translation, acts as “gas pedal”, part of the complex (eIF4E) can bind to 4E-BP which rate limits

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7
Q

4E-BP

A

protein that binds part of eIF4F complex to prevent protein synthesis, is phosphorylated/deactivated by mTOR

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8
Q

Rheb

A

small GTPase that activates mTORC1, is stimulated by nutrients

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9
Q

TSC1/C2

A

inhibits Rheb so inhibits mTORC1, TSC1/C2 is inhibited by insulin

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10
Q

LCAT

A

enzyme that converts free cholesterol into cholesteryl ester, which is then sequestered into the core of a lipoprotein particle

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11
Q

“gas pedal” of protein translation

A

eIF4F complex

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12
Q

PKR

A

phosphorylates eIF2 and stops protein synthesis, kinase secreted by cancer/tumors

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13
Q

Akt

A

phosphorylates TSC2 which inactivates the complex

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14
Q

AMPK

A

activated by rising AMP and falling ATP, activation of AMPK activates TSC1/2, switches on catabolic pathways and switches off anabolic pathways (such as inhibition of ACC leading to decrease malonyl-CoA levels and increased mitochondrial beta oxidation)

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15
Q

Berberine and EGCG

A

compounds that activate AMPK

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16
Q

Autophagy

A

process that targets cellular components for lysosomal degradation in response to cellular damage and starvation

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17
Q

Sirtuins

A

NAD+-dependent protein deacetylases that mediate many of the effects of caloric restriction, they can act as nutrient sensors

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18
Q

Activation of sirtuins

A

positive impacts on metabolism including enhanced fatty acid oxidation and gluconeogenesis (liver), increased mitochondrial activity and insulin sensitivity (muscle), and improved glucose-induced insulin release (pancreas)

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19
Q

Components of circadian clock

A

CLOCK/Bmal1 drive the expression of circadian genes and the repressors Cry and Per. Cry/Per bind and inhibit CLOCK/Bmal1.

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20
Q

functions of circadian clock

A

The clock is reset through ubiquitination and proteosomal degradation of the repressor complex. Circadian rhythms establish cyclical acetylation of chromatin with CLOCK
acting as acetylase and Sirt1 as deacetylase (Sirt1 represses circadian gene expression)

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21
Q

nuclear receptors affecting circadian rhythm?

A

nutrient sensing by nuclear hormone receptors: PPAR α can activate the expression of BMAL and both PPARϒ or -α can bind to the REV-ERB promoter

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22
Q

Hepcidin

A

prevents uptake of iron by degrading ferroportin, trapping iron in the intestine

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23
Q

Anemia of chronic disease

A

Pro-inflammatory cytokine (IL-6) causes large secretion of hepcidin which leads to reduced circulating iron levels (defense against microorganisms need for iron)

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24
Q

Hereditary iron overload disease

A

Mutations in HFE, TfR2 or hepcidin can lead to iron overload

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25
Q

Ferritin

A

a shell like protein that can store up to 4500 Fe atoms, can store and release iron in a controlled fashion and act as iron storage buffer

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26
Q

HFE

A

transferrin bound iron with a protein called HFE (High Fe) interacts with TfR2 which leads to secretion of hepcidin (peptide hormone).

27
Q

transferrin

A

circulating Fe3+ is bound to transferrin and delivered to tissues

28
Q

IRE

A

Iron response elements (IREs) - hairpin structure in non coding regions (untranslated region or UTR) of mRNAs for proteins like TfR and ferritin… binding of IRPs to ferritin 5’ inhibits translation, binding of IRPs to TfR 3’ stabilizes the mRNA and promotes translation

29
Q

Results of low iron

A

Active IRPs, ferritin is down regulated (don’t need storage) and TfR is upregulated (cells have more receptors to take in iron)

30
Q

SREBP

A

sterol regulatory element-binding proteins - Transcription factor that regulates expression of genes involved in cholesterol and lipid synthesis

31
Q

how does CR activate sirtuins?

A

CR may activate sirtuins by changing the redox balance between NADH and NAD+. Alternatively, CR may decrease nicotinamide (a product and inhibitor of
SIRT1 catalytic activity)

32
Q

Activators of SIRT1

A

resveratrol, cause partial protection from effects of high fat diet

33
Q

Scap

A

S-cleavage activating protein binds to SREBP, has sterol-sensing domain

34
Q

In sterol-depleted cells:

A

Scap/SREBP complex starts to bind to Sec24 - component of CopII protein coat. Proteases (only in Golgi) S1P and S2P cleave SREBP in 2 places, freeing the active transcription factor (nuclear form). The cleaved SREBP can form dimers and go to nucleus to target lipid metabolism genes

35
Q

High cholesterol conditions:

A

Cholesterol binds to Scap’s sterol-sensing domain which causes a conformational change → prevents interaction with CopII protein. ER retention of Scap/SREBP is enhanced by binding to the ER protein Insig (Insig is a SREBP target gene - SREBP induces the expression of its own negative regulator)

36
Q

Convergent feedback inhibition

A

Newly supplied cholesterol and newly synthesized Insig blocks SREBP from going to nucleus

37
Q

Insig

A

protein that keeps SREBP in the ER during high cholesterol, during low cholesterol Insig is ubiquitinated and degraded

38
Q

HMG CoA reductase

A

first enzyme in cholesterol production pathway, transcription is stimulated by SREBP, enzyme is bound to ER membrane and rapidly degraded in presence of lanosterol, inhibited by AMPK

39
Q

Obesogens

A

Foreign chemical compounds that disrupt normal development and balance of lipid metabolism, obesogens that target the PPARγ/RXR complex mimic the metabolic ligands and activate the receptor leading to upregulation of lipid accumulation which explains their obesogenic effects.

40
Q

Similarities/differences between HMG CoA reductase and SREBP

A

Both bind to Insig, but SREBP is retained in ER and HMG CoA reductase is degraded

41
Q

Effects of obesogens

A
  1. Endocrine disruptions-sex steroids
  2. Hormone dysregulation-cortisol, adiponectin, and leptin
  3. Adipogenic gene upregulation- adipocyte growth
  4. Epigenetic Effects
42
Q

Adiponectin

A

Activates glucose transport/inhibits gluconeogenesis via AMPK, activates fatty acid oxidation and decreases inflammation through PPARα pathway, enhances insulin sensitivity through phosphorylation of insulin receptor and IRS-1.
So adiponectin is a good thing, and decreasing this hormone can lead to obesity.

43
Q

Lipoproteins

A

Lipoproteins are macromolecules consisting of an outer soluble lipid-protein shell enclosing a droplet of insoluble lipids

44
Q

Chylomicrons

A

transport fat from the intestines into the bloodstream

45
Q

ApoC-II

A

ApoC-II activates lipoprotein lipase which catalyzes hydrolysis of TG

46
Q

ApoB48/remnant receptor

A

takes leftovers/chylomicron remnants back into the liver

47
Q

Lipoprotein lipase

A

catalyzes the hydrolysis of TG

48
Q

Familial chylomicronemia syndrome

A

extremely elevated levels of TG in the blood, can occur due to lipoprotein lipase deficiency or ApoC-II deficiency

49
Q

Mendelian randomization

A

can be used to predict clinical effects of therapeutic intervention on disease biomarkers

50
Q

Familial hypercholesterolemia

A

caused by defects in LDL receptor

51
Q

Nampt

A

activated by caloric restriction, which decreases nicotinamide levels and increases Sirt1 activity

52
Q

CPT1

A

helps with fatty acid oxidation

53
Q

ApoA1

A

component of HDL, activates LCAT

54
Q

ABCA1

A

transports cholesterol out of cells

55
Q

SR-B1

A

transport cholesterol out of cells?

56
Q

ApoB100

A

synthesis of VLDL, in liver

57
Q

ApoB48

A

synthesis of chylomicrons, in small intestine

58
Q

IDL

A

VLDL remnant

59
Q

ApoE

A

picked up in circulation, ligand for ApoE receptor

60
Q

ApoA-5

A

promotes VLDL breakdown

61
Q

ApoCIII

A

impairs VLDL clearance (inhibits LPL)

62
Q

Hepatic lipase

A

converts IDL to LDL

63
Q

PCSK9

A

A protein secreted by the liver that targets LDL receptors to lysosomes for degradation

Metabolic Basis of Disease (3 decks)

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