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Subcellular localization and targeting of cathepsin E
1Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
The Journal of Biological Chemistry
|December 9, 1994
Summary
Cathepsin E, an aspartic proteinase, is retained in the endoplasmic reticulum (ER) in mouse and monkey cells. Specific amino acids (1-48) and Cys7 are crucial for this ER retention mechanism.
Area of Science:
- Cell Biology
- Molecular Biology
- Protein Trafficking
Background:
- Cathepsin E is a non-lysosomal aspartic proteinase with largely unknown subcellular localization.
- Understanding protein trafficking is crucial for cellular function and disease research.
Purpose of the Study:
- To determine the subcellular distribution and targeting of cathepsin E.
- To identify the specific protein sequences responsible for cathepsin E's intracellular retention.
Main Methods:
- Transfection of mouse L cells and monkey Cos 1 cells with cathepsin E cDNA.
- Immunofluorescence microscopy and subcellular fractionation.
- Construction and analysis of chimeric proteins between cathepsin E and pepsinogen.
Main Results:
- Cathepsin E was retained intracellularly in L cells and slowly secreted from Cos 1 cells.
- Intracellular cathepsin E exhibited high mannose oligosaccharides, processed to complex types upon secretion.
- Cathepsin E co-localized with an endoplasmic reticulum (ER) marker and distinct membranous vesicles, not lysosomes.
- Amino acids 1-48 of cathepsin E, including Cys7, were identified as critical for ER retention.
Conclusions:
- Intracellular cathepsin E is primarily located in the endoplasmic reticulum in L and Cos 1 cells.
- The N-terminal region (amino acids 1-48) of cathepsin E, particularly Cys7, mediates its ER retention.