title: Ask1 regulates murine platelet granule secretion, thromboxane A2generation, and thrombus formation.
abstract: Mitogen-activated protein kinases (MAPKs) are expressed in platelets and are activated downstream of physiological agonists. Pharmacological and genetic evidence indicate that MAPKs play a significant role in hemostasis and thrombosis, but it is not well understood how MAPKs are activated upon platelet stimulation. Here, we show that apoptosis signal-regulating kinase 1 (ASK1), a member of the MAP3K family, is expressed in both human and murine platelets. ASK1 is rapidly and robustly activated upon platelet stimulation by physiological agonists. Disruption ofAsk1(Ask1-/-) resulted in a marked functional defect in platelets.Ask1-/-platelets showed an impaired agonist-induced integrin αIIbβ3activation and platelet aggregation. Although there was no difference in Ca2+rise, platelet granule secretion and thromboxane A2(TxA2) generation were significantly attenuated inAsk1-/-platelets. The defective granule secretion observed inAsk1-/-platelets was a consequence of impaired TxA2generation. Biochemical studies showed that platelet agonists failed to activate p38 MAPK inAsk1-/-platelets. On the contrary, activation of c-JunN-terminal kinases and extracellular signal-regulated kinase 1/2 MAPKs was augmented inAsk1-/-platelets. The defect in p38 MAPK results in failed phosphorylation of cPLA2inAsk1-/-platelets and impaired platelet aggregate formation under flow. The absence of Ask1 renders mice defective in hemostasis as assessed by prolonged tail-bleeding times. Deletion ofAsk1also reduces thrombosis as assessed by delayed vessel occlusion of carotid artery after FeCl3-induced injury and protects against collagen/epinephrine-induced pulmonary thromboembolism. These results suggest that the platelet Ask1 plays an important role in regulation of hemostasis and thrombosis.
authors.affiliation: Cardeza Center for Vascular Biology, Department of Medicine, Thomas Jefferson University, Philadelphia, PA.
authors.forename: Meghna U
authors.initials: MU
authors.lastname: Naik
authors.affiliation: Cardeza Center for Vascular Biology, Department of Medicine, Thomas Jefferson University, Philadelphia, PA.
authors.forename: Pravin
authors.initials: P
authors.lastname: Patel
authors.affiliation: Cardeza Center for Vascular Biology, Department of Medicine, Thomas Jefferson University, Philadelphia, PA.|Department of Biological Sciences, University of Delaware, Newark, DE.
authors.forename: Randall
authors.initials: R
authors.lastname: Derstine
authors.affiliation: Department of Biological Sciences, University of Delaware, Newark, DE.
authors.forename: Ramya
authors.initials: R
authors.lastname: Turaga
authors.affiliation: Cardeza Center for Vascular Biology, Department of Medicine, Thomas Jefferson University, Philadelphia, PA.
authors.forename: Xi
authors.initials: X
authors.lastname: Chen
authors.affiliation: Cardeza Center for Vascular Biology, Department of Medicine, Thomas Jefferson University, Philadelphia, PA.
authors.forename: Kalyan
authors.initials: K
authors.lastname: Golla
authors.affiliation: Department of Chemical and Biological Engineering, Colorado School of Mines, Golden, CO; and.
authors.forename: Keith B
authors.initials: KB
authors.lastname: Neeves
authors.affiliation: Laboratory of Cell Signaling, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan.
authors.forename: Hidenori
authors.initials: H
authors.lastname: Ichijo
authors.affiliation: Cardeza Center for Vascular Biology, Department of Medicine, Thomas Jefferson University, Philadelphia, PA.|Department of Biological Sciences, University of Delaware, Newark, DE.
authors.forename: Ulhas P
authors.identifier: 0000-0001-7556-444X
authors.initials: UP
authors.lastname: Naik
mesh_terms: D000818:Animals; D001777:Blood Coagulation / Q000502:physiology*; D001792:Blood Platelets / Q000378:metabolism*; D003594:Cytoplasmic Granules / Q000378:metabolism; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D048848:MAP Kinase Kinase Kinase 5 / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D015539:Platelet Activation / Q000502:physiology*; D013928:Thromboxane A2 / Q000096:biosynthesis*
chemical_list: D013928:Thromboxane A2; D048848:MAP Kinase Kinase Kinase 5; C482859:Map3k5 protein, mouse