B lymphocytes from patients with I-cell disease (ICD) maintain normal cellular levels of lysosomal enzymes despite a deficiency of the enzyme UDP-N-acetylglucosamine: lysosomal enzyme N-acetylglucosamine-1-phosphotransferase. We find that an ICD B lymphoblastoid cell line targets about 45% of the lysosomal protease cathepsin D to dense lysosomes. This targeting occurs in the absence of detectable mannose 6-phosphate residues on the cathepsin D and is not observed in ICD fibroblasts. The secretory protein pepsinogen, which is closely related to cathepsin D in both amino acid sequence and three-dimensional structure, is mostly excluded from dense lysosomes, indicating that the lymphoblast targeting pathway is specific. Carbohydrate residues are not required for lysosomal targeting, since a non-glycosylated mutant cathepsin D is sorted with comparable efficiency to the wild type protein. Analysis of a number of cathepsin D/pepsinogen chimeric proteins indicates that an extensive polypeptide determinant in the cathepsin D carboxyl lobe can confer efficient lysosomal sorting when introduced into the pepsinogen sequence. This determinant overlaps but is not identical to the recognition marker for phosphotransferase. These results indicate that a specific protein recognition event underlies Man-6-P-independent lysosomal sorting in ICD lymphoblasts.
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1 October 1993
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October 01 1993
Mannose 6-phosphate-independent targeting of lysosomal enzymes in I-cell disease B lymphoblasts.
J N Glickman,
J N Glickman
Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
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S Kornfeld
S Kornfeld
Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Search for other works by this author on:
J N Glickman
Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
S Kornfeld
Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1993) 123 (1): 99–108.
Citation
J N Glickman, S Kornfeld; Mannose 6-phosphate-independent targeting of lysosomal enzymes in I-cell disease B lymphoblasts.. J Cell Biol 1 October 1993; 123 (1): 99–108. doi: https://doi.org/10.1083/jcb.123.1.99
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