Lysosomal Targeting

Question 1

What is step 1?

Answer 1

1) addition of mannose-6-phosphate to N-linked oligosaccharides in the protein in the golgi (lysosomal hydrolyses targeted due to signal patches)

requires:

N-acetylglucosamine phosphotransferase
Phosphodiesterase

Question 2

What is step 2?

Answer 2

2) recognised by M-6-P receptors at trans Golgi and vesicles bud off for transport to lysosomes as a complez

Question 3

What is step 3?

Answer 3

3) low pH of lysosome causes dissociation of protein and receptor

Question 4

What is step 4?

Answer 4

4) receptor recycled, M-6-P removed

Question 5

What is I-Cell disease?

Answer 5

1) Genetic defects in N-acetyl glucosamine phosphotransferase which is used in production of M-6-P
2) lack of M-6-P for target to lysosomes
3) proteins are mistargeted for secretion
4) accumulation of proteins in blood and urine