Pintar - Golgi Trafficking and Endocytosis

Question 1

Zellwegger Syndrome

Answer 1

Defect in peroxisomal receptor recognition of AA targeting sequence in peroxisome-bound proteins. Causes empty peroxisomes, fatal.

Question 2

ER Protein Synthesis Translocation

Answer 2

When free ribosome is synthesizing protein meant for ER, N-terminus binds SRP (signal recognition protein), pausing translation to move the complex to the ER. Binds SRP receptor, continues translation, SRP recycled. Finished proteins are folded + glycosylated.

Question 3

Glycosylation

Answer 3

specific for destination, ex: mannose-6-phosphate for lysosome-bound. Glycosylated proteins transported in vesicles

Question 4

Vesicle Coat Proteins (3)

Answer 4

1) Clathrin - plasma membrane–>endosome, TGNendosome
2) Coatamer I (Cop I)- retrograde transport
3) Coatamer II (Cop II) - ER–>Cis golgi
- cause coating formation when GTP-bound protein binds ER membrane (i.e. Sar-1GTP for CopII)

Question 5

V/T SNARES (Vesicle/Target)

Answer 5

mediate vesicle/target recognition and fusion. V-snare on vesicle recognizes t-snare on target membrane, intertwine and allow merging. Rab (GTP-binding proteins) also bind effectors.
-Botulinum and Tetanus cleave SNARES, preventing vesicle fusion

Question 6

KDEL sequence

Answer 6

AA sequence used for Cop I trans–>cis vesicle retrograde retrieval

Question 7

M6P Receptors

Answer 7

In trans golgi, lysosomal proteins have mannose sugars phosphorylated, marking for transport by M6P receptors recognizing, packaging and transporting.

Question 8

I-Cell disease

Answer 8

Defective phosphatase prevents M6P lysosomal protein marking, leading to secretion of lysosomal enzymes

Question 9

Legionnare’s Disease

Answer 9

Bacteria hijack endosomes, preventing lysosomal fusion and degradation

Question 10

Pathways for receptors following endocytosis (3)

Answer 10

1) return to cell surface
2) Recycling and degrading in lysosome
3) transcytosis to another cell

Question 11

Adaptins

Answer 11

Intermediate binding between clathrin and cell receptors. Important since adaptin mutation can cause defect despite healthy clathrin and receptors

Question 12

Protein Transportation into Nucleus via RanGDP

Answer 12

Protein with nuclear localization sequence binds importin a/b complex and is transported into nucleus. RanGTP binds importin, causing protein release. RanGTP-importin complex transports back to cytoplasm, RanGAP (GTPase activating protein) converts RanGTP–>GDP, releasing importin. Reset.