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von Willebrand factor storage requires intact prosequence cleavage site
A M Journet1, S Saffaripour, E M Cramer
1Center for Hemostasis and Thrombosis Research, New England Medical Center, Boston, MA 02111.
European Journal of Cell Biology
|February 1, 1993
Summary
Prosequence cleavage is essential for storing von Willebrand factor (vWf) in specialized granules. Without this cleavage, vWf is not efficiently stored and may be degraded, highlighting the importance of this step for regulated secretion.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Von Willebrand factor (vWf) multimers are stored in Weibel-Palade bodies (WPBs) in endothelial cells.
- Regulated secretion pathways can form vWf-containing granules similar to WPBs.
- vWf lacking its prosequence is not stored.
Purpose of the Study:
- To investigate the role of prosequence cleavage in vWf storage.
- To determine if large multimer formation is sufficient for vWf storage.
- To understand the cellular fate of uncleaved pro-vWf.
Main Methods:
- Mutagenesis of the prosequence cleavage site (Arg -1 to Gly).
- Transfection of mutant pro-vWf into RIN 5F and AtT-20 cells.
- Analysis of vWf multimerization, intracellular storage (Endo-H resistance), and localization (immunofluorescence, electron microscopy, immunocytochemistry).
Main Results:
- Mutant pro-vWf formed large multimers but was not stored efficiently.
- No significant intracellular Endo-H-resistant vWf was detected.
- Weibel-Palade body-like structures were absent; mutant pro-vWf localized to the ER, granules, and lysosomes.
Conclusions:
- Formation of large vWf multimers alone is insufficient for efficient storage.
- Prosequence cleavage is a critical requirement for vWf storage in regulated secretory pathways.
- Lack of prosequence cleavage may lead to degradation of pro-vWf.