1. Fibroblast cells from patients W, X, Y, and Z, each of whom has a different...

 

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1. Fibroblast cells from patients W, X, Y, and Z, each of whom has a different inherited defect, all contain "inclusion bodies," which are lysosomes filled with undigested material. You wish to identify the cellular basis of these defects. The possibilities are: 1. a defect in one of the lysosomal hydrolases 2. a defect in the phosphotransferase that is required for mannose-6-phosphate tagging of the lysosomal hydrolases 3. a defect in the mannose-6-phosphate receptor Cell Line Normal W X Y Z W= X= + indicates that the cells appear normal; - indicates that the cells still have inclusion bodies Indicate which defect (1, 2, 3) each patient (W, X, Y, Z) is most likely to have. Y= From normal Medium From From cultures cultures cells of W cells of X cells Z= From cultures of Y cells When you incubate some of these mutant fibroblasts From in a medium in which normal cells have been cultures of Z cells grown, you find that the inclusion bodies disappear. -Because of these results, you suspect that the constitutive exocytic pathway in normal cells is secreting lysosomal hydrolases that are being taken up by the mutant cells. (It is known that some mannose-6-phosphate receptor molecules are found + in the plasma membrane.) You incubate cells from each patient with medium from normal cells and medium from each of the other mutant cell cultures, and get the results summarized in the Table. 1. Fibroblast cells from patients W, X, Y, and Z, each of whom has a different inherited defect, all contain "inclusion bodies," which are lysosomes filled with undigested material. You wish to identify the cellular basis of these defects. The possibilities are: 1. a defect in one of the lysosomal hydrolases 2. a defect in the phosphotransferase that is required for mannose-6-phosphate tagging of the lysosomal hydrolases 3. a defect in the mannose-6-phosphate receptor Cell Line Normal W X Y Z W= X= + indicates that the cells appear normal; - indicates that the cells still have inclusion bodies Indicate which defect (1, 2, 3) each patient (W, X, Y, Z) is most likely to have. Y= From normal Medium From From cultures cultures cells of W cells of X cells Z= From cultures of Y cells When you incubate some of these mutant fibroblasts From in a medium in which normal cells have been cultures of Z cells grown, you find that the inclusion bodies disappear. -Because of these results, you suspect that the constitutive exocytic pathway in normal cells is secreting lysosomal hydrolases that are being taken up by the mutant cells. (It is known that some mannose-6-phosphate receptor molecules are found + in the plasma membrane.) You incubate cells from each patient with medium from normal cells and medium from each of the other mutant cell cultures, and get the results summarized in the Table.

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atient W has a defect in the mannose6phosphate receptor Due to this th... View the full answer