title: Characterization of a Novel Integrin Binding Protein, VPS33B, Which Is Important for Platelet Activation and In Vivo Thrombosis and Hemostasis.
abstract: BACKGROUND
  Integrins are heterodimeric (α/β) 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.
  
  
  RESULTS
  Here, we show that VPS33B, a member of the Sec1/Munc18 family, binds directly to the integrin β subunit. Overexpression of VPS33B in Chinese hamster ovary cells potentiated αIIbβ3 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. αIIbβ3-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 RhoA-ROCK-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.
authors.affiliation: From Division of Cardiovascular Medicine, Saha Cardiovascular Research Center (B.X., G.Z., S.Y., R.Z., S.S.S., Z.L.), Department of Molecular and Cellular Biochemistry (S.Y., S.W.W.), and Markey Cancer Center (C.H.), University of Kentucky, Lexington; Department of Biochemistry and Molecular Biology, Mayo Clinic in Arizona, Scottsdale (J.L.); Department of Oncology (M.T.) and Jiangsu Institute of Hematology, Department of Hematology (C.R.), First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China; and Lexington Veterans Affairs Medical Center, Lexington, KY (S.S.S.).
authors.forename: Binggang
authors.initials: B
authors.lastname: Xiang
authors.affiliation: From Division of Cardiovascular Medicine, Saha Cardiovascular Research Center (B.X., G.Z., S.Y., R.Z., S.S.S., Z.L.), Department of Molecular and Cellular Biochemistry (S.Y., S.W.W.), and Markey Cancer Center (C.H.), University of Kentucky, Lexington; Department of Biochemistry and Molecular Biology, Mayo Clinic in Arizona, Scottsdale (J.L.); Department of Oncology (M.T.) and Jiangsu Institute of Hematology, Department of Hematology (C.R.), First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China; and Lexington Veterans Affairs Medical Center, Lexington, KY (S.S.S.).
authors.forename: Guoying
authors.initials: G
authors.lastname: Zhang
authors.affiliation: From Division of Cardiovascular Medicine, Saha Cardiovascular Research Center (B.X., G.Z., S.Y., R.Z., S.S.S., Z.L.), Department of Molecular and Cellular Biochemistry (S.Y., S.W.W.), and Markey Cancer Center (C.H.), University of Kentucky, Lexington; Department of Biochemistry and Molecular Biology, Mayo Clinic in Arizona, Scottsdale (J.L.); Department of Oncology (M.T.) and Jiangsu Institute of Hematology, Department of Hematology (C.R.), First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China; and Lexington Veterans Affairs Medical Center, Lexington, KY (S.S.S.).
authors.forename: Shaojing
authors.initials: S
authors.lastname: Ye
authors.affiliation: From Division of Cardiovascular Medicine, Saha Cardiovascular Research Center (B.X., G.Z., S.Y., R.Z., S.S.S., Z.L.), Department of Molecular and Cellular Biochemistry (S.Y., S.W.W.), and Markey Cancer Center (C.H.), University of Kentucky, Lexington; Department of Biochemistry and Molecular Biology, Mayo Clinic in Arizona, Scottsdale (J.L.); Department of Oncology (M.T.) and Jiangsu Institute of Hematology, Department of Hematology (C.R.), First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China; and Lexington Veterans Affairs Medical Center, Lexington, KY (S.S.S.).
authors.forename: Rui
authors.initials: R
authors.lastname: Zhang
authors.affiliation: From Division of Cardiovascular Medicine, Saha Cardiovascular Research Center (B.X., G.Z., S.Y., R.Z., S.S.S., Z.L.), Department of Molecular and Cellular Biochemistry (S.Y., S.W.W.), and Markey Cancer Center (C.H.), University of Kentucky, Lexington; Department of Biochemistry and Molecular Biology, Mayo Clinic in Arizona, Scottsdale (J.L.); Department of Oncology (M.T.) and Jiangsu Institute of Hematology, Department of Hematology (C.R.), First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China; and Lexington Veterans Affairs Medical Center, Lexington, KY (S.S.S.).
authors.forename: Cai
authors.initials: C
authors.lastname: Huang
authors.affiliation: From Division of Cardiovascular Medicine, Saha Cardiovascular Research Center (B.X., G.Z., S.Y., R.Z., S.S.S., Z.L.), Department of Molecular and Cellular Biochemistry (S.Y., S.W.W.), and Markey Cancer Center (C.H.), University of Kentucky, Lexington; Department of Biochemistry and Molecular Biology, Mayo Clinic in Arizona, Scottsdale (J.L.); Department of Oncology (M.T.) and Jiangsu Institute of Hematology, Department of Hematology (C.R.), First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China; and Lexington Veterans Affairs Medical Center, Lexington, KY (S.S.S.).
authors.forename: Jun
authors.initials: J
authors.lastname: Liu
authors.affiliation: From Division of Cardiovascular Medicine, Saha Cardiovascular Research Center (B.X., G.Z., S.Y., R.Z., S.S.S., Z.L.), Department of Molecular and Cellular Biochemistry (S.Y., S.W.W.), and Markey Cancer Center (C.H.), University of Kentucky, Lexington; Department of Biochemistry and Molecular Biology, Mayo Clinic in Arizona, Scottsdale (J.L.); Department of Oncology (M.T.) and Jiangsu Institute of Hematology, Department of Hematology (C.R.), First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China; and Lexington Veterans Affairs Medical Center, Lexington, KY (S.S.S.).
authors.forename: Min
authors.initials: M
authors.lastname: Tao
authors.affiliation: From Division of Cardiovascular Medicine, Saha Cardiovascular Research Center (B.X., G.Z., S.Y., R.Z., S.S.S., Z.L.), Department of Molecular and Cellular Biochemistry (S.Y., S.W.W.), and Markey Cancer Center (C.H.), University of Kentucky, Lexington; Department of Biochemistry and Molecular Biology, Mayo Clinic in Arizona, Scottsdale (J.L.); Department of Oncology (M.T.) and Jiangsu Institute of Hematology, Department of Hematology (C.R.), First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China; and Lexington Veterans Affairs Medical Center, Lexington, KY (S.S.S.).
authors.forename: Changgeng
authors.initials: C
authors.lastname: Ruan
authors.affiliation: From Division of Cardiovascular Medicine, Saha Cardiovascular Research Center (B.X., G.Z., S.Y., R.Z., S.S.S., Z.L.), Department of Molecular and Cellular Biochemistry (S.Y., S.W.W.), and Markey Cancer Center (C.H.), University of Kentucky, Lexington; Department of Biochemistry and Molecular Biology, Mayo Clinic in Arizona, Scottsdale (J.L.); Department of Oncology (M.T.) and Jiangsu Institute of Hematology, Department of Hematology (C.R.), First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China; and Lexington Veterans Affairs Medical Center, Lexington, KY (S.S.S.).
authors.forename: Susan S
authors.initials: SS
authors.lastname: Smyth
authors.affiliation: From Division of Cardiovascular Medicine, Saha Cardiovascular Research Center (B.X., G.Z., S.Y., R.Z., S.S.S., Z.L.), Department of Molecular and Cellular Biochemistry (S.Y., S.W.W.), and Markey Cancer Center (C.H.), University of Kentucky, Lexington; Department of Biochemistry and Molecular Biology, Mayo Clinic in Arizona, Scottsdale (J.L.); Department of Oncology (M.T.) and Jiangsu Institute of Hematology, Department of Hematology (C.R.), First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China; and Lexington Veterans Affairs Medical Center, Lexington, KY (S.S.S.).
authors.forename: Sidney W
authors.initials: SW
authors.lastname: Whiteheart
authors.affiliation: From Division of Cardiovascular Medicine, Saha Cardiovascular Research Center (B.X., G.Z., S.Y., R.Z., S.S.S., Z.L.), Department of Molecular and Cellular Biochemistry (S.Y., S.W.W.), and Markey Cancer Center (C.H.), University of Kentucky, Lexington; Department of Biochemistry and Molecular Biology, Mayo Clinic in Arizona, Scottsdale (J.L.); Department of Oncology (M.T.) and Jiangsu Institute of Hematology, Department of Hematology (C.R.), First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China; and Lexington Veterans Affairs Medical Center, Lexington, KY (S.S.S.).
authors.forename: Zhenyu
authors.initials: Z
authors.lastname: Li
mesh_terms: D000818:Animals; D016466:CHO Cells; D002352:Carrier Proteins / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D006487:Hemostasis / Q000502:physiology*; D016023:Integrins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D015539:Platelet Activation / Q000502:physiology*; D021381:Protein Transport / Q000502:physiology; D013927:Thrombosis / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000096:biosynthesis*
chemical_list: D002352:Carrier Proteins; D016023:Integrins; C411584:VPS33B protein, human; D033921:Vesicular Transport Proteins
keywords: VPS33B protein; blood platelets; hemostasis; integrins; mouse; platelet aggregation; signal transduction; thrombosis