Lipoprotein Assembly Flashcards

1
Q

apoB

A

ApoB is the main protein on CM, VLDL, and LDL

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2
Q

ApoB100 vs apoB48

A

ApoB100: stabilizes VLDL and LDL, produced in liver and present on VLDL and LDL
1. structural protein
2. LDL uptake, recognized by LDL receptor

ApoB48: N-terminal of ApoB100, 48% of ApoB100, cannot bind to LDL because it has no C-terminal, on VLDL/chylomicron remnants is recognized by the remnant
1. Structural protein
2. not recognized by LDL receptor

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3
Q

How is ApoB48 produced

A

Transcribed from the same gene as apoB100, but under goes RNA editing in the intestine

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4
Q

Where are Cm/VLDL assembled? structures of CM,VLDL,LDL

A

CM in intestine
VLDL in liver

CM/VLDL:
* Particles composed of a TG-rich core with a small content of CE, a surface monolayer of phospholipid and cholesterol and
apolipoproteins
* Although CM and VLDL are produced by different tissues, the
process is similar

LDL: Produced in circulation from VLDL, CE-rich core

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5
Q

5 steps

model of VLDL/CM assembly? does it require co-translational or post-translational lipidation?

A

Required co-translation and post-translational lipidation
1. Generation of lumenal lipid droplets
2.Translation/ translocation of apoB into ER lumen
* Co-translational addition of lipids to apoB –> nascent CM/VLDL
3. Post-translational addition of lipids (fusion) to nascent CM/VLDL –> mature CM/VLDL
* apoB is fully translocated
4. Secretion into circulation
5. Addition of other apolipoproteins (apoE, apoCII) occurs in the circulation

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6
Q

What protein is needed for VLDL/CM assembly

A

MTP
Facilitates the formation of CM/CLDL by catalyzing the transfer of TG and PL

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7
Q

Abetalipoproteinemia (description, mutation in what protein, symptoms, treatment)

A

Genetic disease of lipoprotein assembly (CM/CLDL)

Mutation in MTP

absence of apoB-containing plasma lipoproteins (CM, VLDL, and LDL)
low concentration of TG and cholesterol in blood

Failure to grow in infancy
fatty stools
loss of vision
vitamin E deficiency

Low fat diet, vitamin E supplement

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8
Q

MTP inhibitor

A

Cholesterol is reduced, has some toxic effects
Increased ALT indicates liver damage
also caused fatty liver

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9
Q

What does increased ALT indicate

A

Indicates liver damage

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10
Q

MTP function

A

Facilitates the formation of CM/CLDL by catalyzing the transfer of TG and PL

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