A role for Rab10 in von Willebrand factor release discovered by an AP-1 interactor screen in C. elegans.
BACKGROUND
Endothelial von Willebrand factor (VWF) mediates platelet adhesion and acts as a protective chaperone to clotting factor VIII. Rapid release of highly multimerized VWF is particularly effective in promoting hemostasis. To produce this protein, an elaborate biogenesis is required, culminating at the trans-Golgi network (TGN) in storage within secretory granules called Weibel-Palade bodies (WPB). Failure to correctly form these organelles can lead to uncontrolled secretion of low-molecular-weight multimers of VWF. The TGN-associated adaptor AP-1 and its interactors clathrin, aftiphilin and γ-synergin are essential to initial WPB formation at the Golgi apparatus, and thus to VWF storage and secretion.


OBJECTIVE
To identify new proteins implicated in VWF storage and/or secretion.


METHODS
A genomewide RNA interference (RNAi) screen was performed in the Nematode C. elegans to identify new AP-1 genetic interactors.


RESULTS
The small GTPase Rab10 was found to genetically interact with a partial loss of function of AP-1 in C. elegans. We investigated Rab10 in human primary umbilical vein endothelial cells (HUVECs). We report that Rab10 is enriched at the Golgi apparatus, where WPB are formed, and that in cells where Rab10 expression has been suppressed by siRNA, VWF secretion is altered: the amount of rapidly released VWF was significantly reduced. We also found that Rab8A has a similar function.


CONCLUSIONS
Rab10 and Rab8A are new cytoplasmic factors implicated in WPB biogenesis that play a role in generating granules that can rapidly respond to secretagogue.
INSERM Avenir team Trafic intracellulaire et polarité chez C. elegans, Rennes, France. gmichaux@univ-rennes1.fr
G
G
Michaux
C E F
CE
Dyer
T D
TD
Nightingale
E
E
Gallaud
S
S
Nurrish
D F
DF
Cutler
D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D006801:Humans; D016133:Polymerase Chain Reaction; D034622:RNA Interference; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000502:physiology*; D014841:von Willebrand Factor / Q000378:metabolism*
D018808:Transcription Factor AP-1; D014841:von Willebrand Factor; C538901:Rab10 protein, human; D020691:rab GTP-Binding Proteins