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Synaptotagmin-like protein 1 interacts with the GTPase-activating protein Rap1GAP2 and regulates dense granule secretion in platelets
Alternative Title
Slp1 regulates platelet secretion
Date Issued
2009-08-13
Date Available
2014-09-08T08:02:48Z
Abstract
The small guanine-nucleotide–binding protein Rap1 plays a key role in platelet aggregation and hemostasis, and we recently identified Rap1GAP2 as the only GTPase-activating protein of Rap1 in platelets. In search of Rap1GAP2-associated proteins, we performed yeast-2-hybrid screening and found synaptotagmin-like protein 1 (Slp1) as a new binding partner. We confirmed the interaction of Rap1GAP2 and Slp1 in transfected COS-1 and HeLa cells and at endogenous level in human platelets. Mapping studies showed that Rap1GAP2 binds through amino acids T524-K525-X-T527 within its C-terminus to the C2A domain of Slp1. Slp1 contains a Rab27-binding domain, and we demonstrate that Rap1GAP2, Slp1, and Rab27 form a trimeric complex in transfected cells and in platelets. Purified Slp1 dose-dependently decreased dense granule secretion in streptolysin-O–permeabilized platelets stimulated with calcium or guanosine 5′-O-[gamma-thio] triphosphate. The isolated C2A domain of Slp1 had a stimulatory effect on granule secretion and reversed the inhibitory effect of full-length Slp1. Purified Rap1GAP2 augmented dense granule secretion of permeabilized platelets, whereas deletion of the Slp1-binding TKXT motif abolished the effect of Rap1GAP2. We conclude that Slp1 inhibits dense granule secretion in platelets and that Rap1GAP2 modulates secretion by binding to Slp1.
Sponsorship
Science Foundation Ireland
Other Sponsorship
Deutsche Forschungsgemeinschaft
Excellence Cluster Cardio-Pulmonary System
Type of Material
Journal Article
Publisher
American Society of Hematology
Journal
Blood
Volume
114
Issue
7
Start Page
1396
End Page
1404
Copyright (Published Version)
2009 The American Society of Hematology
Language
English
Status of Item
Peer reviewed
This item is made available under a Creative Commons License
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