N-3 polyunsaturated fatty acid, lipid microclusters, and Vit E

Question 1

lipid rafts

Answer 1

cholesterol-dependent signaling or sphingolipid-cholesterol-enriched microdomains that compartmentalize signalling proteins

Question 2

cholesterol-dependent signaling or sphingolipid-cholesterol-enriched microdomains that compartmentalize signalling proteins

Answer 2

lipid rafts

Question 3

lipid rafts are generally nanoscale, but can form micron scale domains upon ?

Answer 3

receptor ligation

Question 4

N-3 PUFA directly binding G-protein coupled receptor (GPR) 120 results in ?

Answer 4

anti-inflammatory effects in macrophages important in regulating insulin signaling in obesity

Question 5

N-3 PUFA acyl chains, upon enzymatic release from the membrane, regulate eicosanoid production and can serve as precursors for the synthesis of lipid mediators known as ?, ? and ?

Answer 5

resolvins, protectins, and maresins

Question 6

downstream of the plasma membrane, n-3 PUFAs exert their effects by targeting ? to modify gene expression

Answer 6

transcription factors

Question 7

presence of multiple double bonds in n-3 PUFA acyl chains gives a high/low degree of conformational freedom

Answer 7

high

Question 8

Our understanding of DHAs structure comes from ? and ?

Answer 8

2H NMR (experimental) and MD simulations (computational)

Question 9

In NMR studies, DHA is typically esterified to PC or PE in the ? position while palmitic or stearing acid occupies the ? position

Answer 9

DHA occupies sn-2. palmitic or stearing acid occupies the sn-1 position

Question 10

the fundamental property that distinguishes n-3 PUFA from less unsaturated fatty acids

Answer 10

tremendously high disorder

Question 11

origin of disorder in n-3 PUFAs

Answer 11

low energy barrier about C-C single bonds in the repeating units that link C=C double bonds

Question 12

indicative of low microviscosity, order parameters measured by solid state 2H NMR throughout almost all of the DHA chain in the sn-2 position are large/small

Answer 12

small. S_CD ~ 0.01

Question 13

order within the stearic acid chain at the sn-1 position is increased/decreased by the presence of DHA in sn-2 position

Answer 13

decreased order (~10%)

Question 14

reduction in stearic acid order as a result of DHA is more significant in the upper/lower half

Answer 14

lower half

Question 15

rapid isomerization of DHA chain. explores entire conformational space in ?

Answer 15

~ 10 nanoseconds

Question 16

DHA MD simulations reveal bent configurations where ____

Answer 16

terminal methyl group approaches hydrophobic-philic and redistribution of the lower portion of DHA chains toward the interface

Question 17

DHA acyl chains generally increase/decrease microviscosity (to different degrees in different cell types)

Answer 17

decrease

Question 18

DHA effects on physical properties of bilayers

Answer 18

reduced membrane thickness, increased compressibility, permeability, fusion and flip-flop

Question 19

DHA has high/low affinity for cholesterol

Answer 19

low affinity

Question 20

rapid interconversion between torsional states undergone by PUFAs pushes the rigid steroid moiety away was shown by ?

Answer 20

low solubility and binding coefficients for cholesterol in polyunsaturated membranes

Question 21

PUFA induced reduction in cholesterol affinity is more significant in PE or PC? why?

Answer 21

PE. tighter packing associated with smaller headgroup brings sterol and PUFA closer together

Question 22

sphingolipid had high/low affinity for cholesterol. why?

Answer 22

high affinity. saturated and adopt largely linear conformation

Question 23

in the extreme case of bilayers comprised of phospholipids with a PUFA chain at both sn-1 and sn-2 positions, sterol can be forced into an unusual position where?

Answer 23

deep within the interior of the bilayer

Question 24

DHA remodels lipid raft-like domains that are nano-sized in a manner that is dependent upon the ____ headgroup. How was this observed?

Answer 24

phospholipid. observed using solid state 2H NMR, DSC, and detergent extraction experiments

Question 25

Majority of PDPE was found to segregate into domains high/low in SM and cholesterol

Answer 25

low

Question 26

introduction of cholesterol increased/decreased the order of PDPE more significantly than that seen with POPE. How was this observed?

Answer 26

increased. From 2H NMR spectra for analogs of PE perdeuterated in the sn-1 chain at 40 C

Question 27

More than 3x as much PDPE (70%) as POPE (22%) was isolated in detergent soluble (nonraft) fractions while almost all of the cholesterol and SM (>90%) were isolated in detergent resistant (raft) fractions. How was this observed?

Answer 27

detergent extraction experiments

Question 28

PDPC was shown to directly infiltrate into SM and cholesterol rich domains. This was observed using?

Answer 28

2H NMR (williams 2012)

Question 29

what is the significance of the formation of inverted hexagonal (Hii) phase that becomes accentuated with increasing levels of acyl chain saturation

Answer 29

??? (Dekker, Kessel, Klomp 1983)

Question 30

XX% of EPA containing PC was found in raft-like domains compared to 70% for DHA containing PC. Conclusion?

Answer 30

40% of EPA PC. DHA PC is more likely to incorporate into lipid rafts and disrupt organization

Question 31

DRMs and DSMs are isolated from ____ and used to represent native rafts and nonrafts

Answer 31

sucrose gradient fractions of cells subjected to low levels of detergent at cold temperature

Question 32

the most common approach to studying n-3 PUFAs and lipid rafts with DRM and DSM fractions is to either _____ or _____

Answer 32

either treat imortal cells with EPA or DHA or provide animals diets rich in EPA or DHA

Question 33

Most prevalent change resulting from n-3 PUFA uptake? consequence?

Answer 33

arachidonic acid levels decrease. AA itself is a disordered PUFA and its loss could make membrane more packed. Also numerous lipid mediators are derived from AA.

Question 34

Effect of n-3 PUFA uptake on cholesterol

Answer 34

cholesterol is displaced between DRM and DSM fractions. However, no clear consensus on direction of movement

Question 35

In response to DHA treatment, cholesterol levels increase in ____ fractions and decrease in ____ fractions

Answer 35

DEPENDS! sometimes cholesterol moves between DRMs and DSMs in either direction, sometimes can selectively lower with no increase in the other

Question 36

clustering of GM1 molecules is diminished in cell culture treated with DHA/EPA

Answer 36

DHA

Question 37

what is cholera toxin subunit b used for in GM1 molecules

Answer 37

artificial means of inducing lipid rafts on a micron scale

Question 38

translational studies with splenic B220+ B cells show that dietary administration of _____ to animals diminished GM1 clustering in a dose dependent manner

Answer 38

n-3 PUFAs

Question 39

polarization microscopy experiments revelaed that n-3 PUFAs enhanced/diminished membrane packing in B and T lymphocytes

Answer 39

enhanced

Question 40

fat-1 transgenic mice have high/low levels of endogenous n-3 PUFAs. why?

Answer 40

high levels due to a desaturase that converts n-6 to n-3

Question 41

it was shown that lipid raft accumulation in the immunological synapse was high/low for fat-1 mice compared to control mice

Answer 41

accumulation high for fat-1 mice

Question 42

consequence of accumulation in the immunological synapse

Answer 42

suppressed helper CD4+ Th1 cell activation (potential health benefits in murine models)

Question 43

work in B cells and EL4 lymphomas showed that crosslinking of GM1 microdomains with cholera toxin subunit b had this effect on membrane packing?

Answer 43

enhanced membrane packing with dietary n-3 PUFAs compared to cells not cross-linked with cholera toxin

Question 44

EPA and DHA ethyl esters (modeling prescription supplements) differentially enhanced membrane packing upon formation of lipid microdomains induced by ?

Answer 44

lowering the temperature of cells to 4 C

Question 45

n-3 PUFAs MAY be redistributing cholesterol in a manner that increases/decreases formation of lipid rafts

Answer 45

increases

Question 46

it is possible/not possible that the effects of n-3 PUFAs are independent of cholesterol

Answer 46

possible

Question 47

disrupting lipid raft microdomains in B and T lymphocytes can displace key proteins and suppress function. This has potential health benefits for these types of diseases?

Answer 47

inflammatory diseases including rheumatoid arthritis, renal transplant, or metabolic diseases

Question 48

In B cells, MHC II molecules are displaced from raft-enriched regions of the immunological synapse by n-3 PUFAs. This was observed using ?

Answer 48

confocal and acceptor photobleaching FRET studies. Similar observation for MHC I molecules.

Question 49

In CD4+ T cells, protein kinase C and phospholipase C gamma-1 were displaced from raft-like membranes by n-3 PUFAs. This was observed using ?

Answer 49

biochemical DRM/DSM fractionations and confocal imaging

Question 50

n-3 PUFAs generally have a preference for incorporation into ?

Answer 50

PE's rather than PC's

Question 51

what might happen when n-3 PUFAs incorporate into PC's

Answer 51

PC's are abundant in lipid rafts. this may force cholesterol out of the lipid rafts and into non-raft regions making them more raft like

Question 52

what might happen when n-3 PUFAs incorporate into PE's

Answer 52

rafts are generally not enriched in PE's. n-3 PUFA acyl chains may force cholesterol to move into rafts and make them more packed

Question 53

n-3 PUFAs phase seperate from liquid-ordered lipid raft -like domains when incorporated into ?

Answer 53

incorporated into PE's

Question 54

n-3 PUFAs incorporate directly into liquid liquid-ordered rafts when esterified to ?

Answer 54

esterified to PC's

Question 55

aside from phospholipids, what else might n-3 PUFAs esterify to ?

Answer 55

SM (shown in murine) or cholesterol (shown in cholesterol esters. low membrane solubility)

Question 56

the major lipid soluble antioxidant

Answer 56

Vitamin E (alpha tocopherol)

Question 57

advantage of n-3 PUFA-vitamin E clusters?

Answer 57

could explain how low levels of Vit E can protect relatively large amounts of n-3 PUFA from oxidation

Question 58

chromanol group of Vit E generally resides here?

Answer 58

near the hydrophobic-philic interface of bilayers

Question 59

DMPC location in bilayer

Answer 59

in center at the water interface independent of headgroup or acyl chains

Question 60

emerging evidence for sphingolipid enriched cholesterol-free domains comes from ?

Answer 60

high res mass spectrometry

Question 61

emerging evidence for sphingolipid enriched cholesterol-free domains comes from ?. What was observed?

Answer 61

high res mass spectrometry in cell culture. labelled sphingolipids form micron size domains that are not disrupted by cholesterol depletion. However, they were effectd by disruption of the cytoskeleton.

Question 62

helper t-cells isolated from fat-1 transgenic mice or from mice fed DHA displayed a 50% reduction in phosphatidylinositol 4,5-bisphosphate which contributed toward?

Answer 62

diminished actin remodeling and thereby T cell activation

Question 63

___ and ___ delay opening of the mitochondrial permeability transition pore in the rat myocardium.

Answer 63

EPA and DHA