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Proteolytic processing patterns of prosaposin in insect and mammalian cells
1Division of Human Genetics, Children's Hospital Research Foundation at Children's Hospital Medical Center, Cincinnati, Ohio 45229-3039, USA.
The Journal of Biological Chemistry
|July 19, 1996
Summary
Prosaposin processing is regulated proteolytically to generate different forms, including tetrasaposins and monosaposins, crucial for glycosphingolipid hydrolase activity and neurotrophic functions.
Area of Science:
- Biochemistry
- Neuroscience
- Cell Biology
Background:
- Prosaposin is a precursor protein containing four saposins (A, B, C, D) essential for glycosphingolipid hydrolase activity.
- Prosaposin also functions as a neurotrophic factor, highlighting its multifaceted biological roles.
Purpose of the Study:
- To investigate the proteolytic processing pathways of human prosaposin in various cell types.
- To understand how prosaposin is converted into mature saposins and other functional forms.
Main Methods:
- Metabolic labeling of human prosaposin expressed in insect cells, human fibroblasts, and neuronal stem cells (NT2).
- Analysis of processing intermediates and end products using immunofluorescence and biochemical techniques.
Main Results:
- The major processing pathway in mammalian cells involves tetrasaposins (A-B-C-D) and trisaposins (B-C-D), leading to monosaposins.
- Insect cells predominantly produce disaposins (A-B, C-D, B-C, C-D) from prosaposin.
- Uncleaved prosaposin and precursor tetrasaposins were detected in specific neuronal cell types in mice.
Conclusions:
- Prosaposin processing is a highly regulated proteolytic event.
- Specific cell types exhibit distinct prosaposin processing patterns, yielding prosaposin, tetrasaposins, or monosaposins.
- These findings underscore the regulated production of functional prosaposin derivatives in mammalian cells.