Faculty Collaboration Database

Distinct roles for Rap1b protein in platelet secretion and integrin αIIbβ3 outside-in signaling. J Biol Chem 2011 Nov 11;286(45):39466-77

Date

09/24/2011

Pubmed ID

21940635

Pubmed Central ID

PMC3234770

DOI

10.1074/jbc.M111.239608

Scopus ID

2-s2.0-80655144733 (requires institutional sign-in at Scopus site)   58 Citations

Abstract

Rap1b is activated by platelet agonists and plays a critical role in integrin α(IIb)β(3) inside-out signaling and platelet aggregation. Here we show that agonist-induced Rap1b activation plays an important role in stimulating secretion of platelet granules. We also show that α(IIb)β(3) outside-in signaling can activate Rap1b, and integrin outside-in signaling-mediated Rap1b activation is important in facilitating platelet spreading on fibrinogen and clot retraction. Rap1b-deficient platelets had diminished ATP secretion and P-selectin expression induced by thrombin or collagen. Importantly, addition of low doses of ADP and/or fibrinogen restored aggregation of Rap1b-deficient platelets. Furthermore, we found that Rap1b was activated by platelet spreading on immobilized fibrinogen, a process that was not affected by P2Y(12) or TXA(2) receptor deficiency, but was inhibited by the selective Src inhibitor PP2, the PKC inhibitor Ro-31-8220, or the calcium chelator demethyl-1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis. Clot retraction was abolished, and platelet spreading on fibrinogen was diminished in Rap1b-deficient platelets compared with wild-type controls. The defects in clot retraction and spreading on fibrinogen of Rap1b-deficient platelets were not rescued by addition of MnCl(2), which elicits α(IIb)β(3) outside-in signaling in the absence of inside-out signaling. Thus, our results reveal two different activation mechanisms of Rap1b as well as novel functions of Rap1b in platelet secretion and in integrin α(IIb)β(3) outside-in signaling.

Author List

Zhang G, Xiang B, Ye S, Chrzanowska-Wodnicka M, Morris AJ, Gartner TK, Whiteheart SW, White GC 2nd, Smyth SS, Li Z

Authors

Magdalena Chrzanowska PhD Associate Professor in the Pharmacology and Toxicology department at Medical College of Wisconsin
Gilbert C. White MD Professor in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Adenosine Triphosphate
Animals
Blood Platelets
Chelating Agents
Clot Retraction
Enzyme Activation
Enzyme Inhibitors
Fibrinogen
Indoles
Mice
Mice, Mutant Strains
P-Selectin
Platelet Adhesiveness
Platelet Glycoprotein GPIIb-IIIa Complex
Protein Kinase C
Pyrimidines
Receptors, Purinergic P2Y12
Receptors, Thromboxane A2, Prostaglandin H2
Signal Transduction
rap GTP-Binding Proteins