In my biochemistry class today we did a problem detailing two lysosomal storage diseases.
In the first scenario, a cell line for I-cell disease can synthesize lysosomal hydrolases that are perfectly functional which are then secreted outside of the cell instead of being sort to the lysosome. However there is a mutation that inhibits the the kinase domain that normally phosphorylates Mannose-6-Phosphate (M6P), so there is no M6P-labeling in these cells.
In the second scenario, a cell line for Hurler's disease has a mutation that eliminates one lysosomal glycosidase so that it cannot degradte certain classes of oligosaccharides. This results in the cells of this mutant cell line to have engorged / bloated lysosomes.
Now when these two cell lines are co-cultured in the same flask, it is observed the I-cell culture correctys the defect in the Hurler cell culture, while the Hurler cell culture was not able to correct the defect in the I-cell culture.
My question is how can this phenomenon be explain? And why are the Hurler cells still growing?