title: Protein kinase C mediates platelet secretion and thrombus formation through protein kinase D2.
abstract: Platelets are highly specialized blood cells critically involved in hemostasis and thrombosis. Members of the protein kinase C (PKC) family have established roles in regulating platelet function and thrombosis, but the molecular mechanisms are not clearly understood. In particular, the conventional PKC isoform, PKCα, is a major regulator of platelet granule secretion, but the molecular pathway from PKCα to secretion is not defined. Protein kinase D (PKD) is a family of 3 kinases activated by PKC, which may represent a step in the PKC signaling pathway to secretion. In the present study, we show that PKD2 is the sole PKD member regulated downstream of PKC in platelets, and that the conventional, but not novel, PKC isoforms provide the upstream signal. Platelets from a gene knock-in mouse in which 2 key phosphorylation sites in PKD2 have been mutated (Ser707Ala/Ser711Ala) show a significant reduction in agonist-induced dense granule secretion, but not in α-granule secretion. This deficiency in dense granule release was responsible for a reduced platelet aggregation and a marked reduction in thrombus formation. Our results show that in the molecular pathway to secretion, PKD2 is a key component of the PKC-mediated pathway to platelet activation and thrombus formation through its selective regulation of dense granule secretion.
authors.affiliation: School of Physiology & Pharmacology, Bristol Heart Institute, Bristol, United Kingdom.
authors.forename: Olga
authors.initials: O
authors.lastname: Konopatskaya
authors.forename: Sharon A
authors.initials: SA
authors.lastname: Matthews
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Harper
authors.forename: Karen
authors.initials: K
authors.lastname: Gilio
authors.forename: Judith M E M
authors.initials: JM
authors.lastname: Cosemans
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Williams
authors.forename: Maria N
authors.initials: MN
authors.lastname: Navarro
authors.forename: Deborah A
authors.initials: DA
authors.lastname: Carter
authors.forename: Johan W M
authors.initials: JW
authors.lastname: Heemskerk
authors.forename: Michael
authors.initials: M
authors.lastname: Leitges
authors.forename: Doreen
authors.initials: D
authors.lastname: Cantrell
authors.forename: Alastair W
authors.initials: AW
authors.lastname: Poole
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D005260:Female; D015971:Gene Expression Regulation, Enzymologic; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D008297:Male; D008301:Maleimides / Q000494:pharmacology; D051379:Mice; D018345:Mice, Knockout; D015539:Platelet Activation / Q000187:drug effects / Q000235:genetics*; D010974:Platelet Aggregation / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D000091283:Protein Kinase D2; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D022142:Secretory Vesicles / Q000187:drug effects / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013927:Thrombosis / Q000235:genetics* / Q000378:metabolism
chemical_list: D007211:Indoles; D008301:Maleimides; D000091283:Protein Kinase D2; D047428:Protein Kinase Inhibitors; C099154:ruboxistaurin; D011494:Protein Kinases; D011493:Protein Kinase C