Upon analyzing a sample of cells from a patient, you find the lysosomes to be fi

Question

Upon analyzing a sample of cells from a patient, you find the lysosomes to be filled with undigested material. This observation makes you think that the lysosomes are not functioning properly. Which of the following could account for the defective lysosomes (choose all that apply)?
Question 5 options:

A)
defect in transport of small molecules from digested materials into the cytosol

B)
defect in the mannose-6-phosphate receptor in the Golgi apparatus

C)
defect in the lysosomal proton pump

D)
defect in a digestive enzymes

E)
defect in the process of adding a mannose-6-phosphate signal to lysosomal enzymes

F)
defect in receptor-mediated endocytosis

Explanation / Answer

B) defect in the mannose-6-phosphate receptor in the Golgi apparatus

E) defect in the process of adding a mannose-6-phosphate signal to lysosomal enzymes

Reason:

Lysosomal storage diseases: this disease is mainly involves dysfunction of the lysosomal enzymes due to failure of mannose-6-phosphate to carry out normal signaling to endosome-lysosome as a result soluble lysosomal enzymes are going to fail to bind with M6P in the lysosomal sacs within cells that digest large molecules. This is due to defect in the mannose-6-phosphate receptor in the Golgi apparatus

Mechanism:

The processing of N-linked oligosaccharides of lysosomal proteins is modified by mannose phosphorylation. Mannose residues are added with N-acetylglucosamine in the cis Golgi network. This is followed by the removal of N-acetylglucosamine, which gives mannose-6-phosphate on the N-linked oligosaccharide, which will be recognized by mannose-6-phosphate receptor in the trans Golgi network. These proteins are now directed to the lysosomes. More specifically, anterograde mechanism regulates the recruitment of the correct Rab to target M6P (mannose-6-phosphat) tagged acid hydrolases to the lysosome as these hydrolases activated by acidic PH in the lysosome. Anterograde targeting of Ran in fusion with SNARE complexes and inhibiting M6P coupling with hydrolases result in M6P pinched off from late endosome.

By the addition of carbohydrates to the serine and threonine residues, the lysosomal proteins are modified (O-linked glycosylation) in the Golgi apparatus by the sequential addition.

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