Characterization of a novel integrin binding protein, vps33b, which is important for platelet activation and in vivo thrombosis and hemostasis

Binggang Xiang, Guoying Zhang, Shaojing Ye, Rui Zhang, Cai Huang, Jun Liu, Min Tao, Changgeng Ruan, Susan S. Smyth, Sidney W. Whiteheart, Zhenyu Li

Research output: Contribution to journalArticlepeer-review

27 Scopus citations


Background-Integrins are heterodimeric (/) membrane proteins that play fundamental roles in many biological processes, for example, cell adhesion and spreading, which are important for platelet function and hemostasis. The molecular mechanism that regulates integrin activation is not completely understood. Methods and Results-Here, we show that VPS33B, a member of the Sec1/Munc18 family, binds directly to the integrin subunit. Overexpression of VPS33B in Chinese hamster ovary cells potentiated IIb3 outside-in signaling but not inside-out signaling. Platelets, from megakaryocyte-And platelet-specific VPS33B conditional knockout mice, had normal morphology, yet their spreading on fibrinogen was impaired and they failed to support clot retraction. Platelet aggregation and ATP secretion in response to low-dose agonists were reduced in the VPS33B knockout mice. IIb3-mediated endocytosis of fibrinogen was also defective. Tail bleeding times and times to occlusion in an FeCl3-induced thrombosis model were prolonged in the VPS33B knockout mice. Furthermore, VPS33B acted upstream of the RhoAROCK-MLC and Rac1-dependent pathways that lead to clot retraction and cell spreading, respectively. Conclusions-Our work demonstrates that vesicular trafficking complexes, containing VPS33B, are a novel class of modifiers of integrin function. Our data also provide insights into the molecular mechanism and treatment of arthrogryposis, renal dysfunction, and cholestasis syndrome.

Original languageEnglish
Pages (from-to)2334-2344
Number of pages11
Issue number24
StatePublished - 2015

Bibliographical note

Funding Information:
We acknowledge Elizabeth Hughes, Keith Childs, Galina Gavrilina, and Debora VanHeyningen and the Transgenic Animal Model Core of the University of Michigan Biomedical Research Core Facilities for generation of chimeric mice via microinjection of blastocysts with ES cells. We thank Mark H. Ginsberg for providing us the αβPy cell line and Junling Liu for providing us the HA-VPS33B constructs. We thank Alan Nurden for helpful suggestions regarding generation of the VPS33B knockout mice and Peter Newman for helpful discussion. This work is supported by the American Society of Hematology Bridge Grant Award (to Z.L.); National Institutes of Health National Heart, Lung, and Blood Institute grants HL68819 (to Z.L.) and HL56652 (to S.W.W.); the American Heart Association Great Rivers Affiliate Grand-in-Aid (to Z. L.); American Heart Association Great Rivers Affiliate Scientist Development Grant (to B.X.); and in part by the National Institutes of Health/National Center for Research Resources Centers of Biomedical Research Excellence in Obesity and Cardiovascular Disease grant P20 RR021954. This work was supported in part by resources provided by the Lexington Veterans Affairs Medical Center.


  • VPS33B protein, mouse
  • blood platelets
  • hemostasis
  • integrins
  • platelet aggregation
  • signal transduction
  • thrombosis

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine
  • Physiology (medical)


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