title: A molecular signaling model of platelet phosphoinositide and calcium regulation during homeostasis and P2Y1 activation.
abstract: To quantify how various molecular mechanisms are integrated to maintain platelet homeostasis and allow responsiveness to adenosine diphosphate (ADP), we developed a computational model of the human platelet. Existing kinetic information for 77 reactions, 132 fixed kinetic rate constants, and 70 species was combined with electrochemical calculations, measurements of platelet ultrastructure, novel experimental results, and published single-cell data. The model accurately predicted: (1) steady-state resting concentrations for intracellular calcium, inositol 1,4,5-trisphosphate, diacylglycerol, phosphatidic acid, phosphatidylinositol, phosphatidylinositol phosphate, and phosphatidylinositol 4,5-bisphosphate; (2) transient increases in intracellular calcium, inositol 1,4,5-trisphosphate, and G(q)-GTP in response to ADP; and (3) the volume of the platelet dense tubular system. A more stringent test of the model involved stochastic simulation of individual platelets, which display an asynchronous calcium spiking behavior in response to ADP. Simulations accurately reproduced the broad frequency distribution of measured spiking events and demonstrated that asynchronous spiking was a consequence of stochastic fluctuations resulting from the small volume of the platelet. The model also provided insights into possible mechanisms of negative-feedback signaling, the relative potency of platelet agonists, and cell-to-cell variation across platelet populations. This integrative approach to platelet biology offers a novel and complementary strategy to traditional reductionist methods.
authors.affiliation: Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, USA.
authors.forename: Jeremy E
authors.initials: JE
authors.lastname: Purvis
authors.forename: Manash S
authors.initials: MS
authors.lastname: Chatterjee
authors.forename: Lawrence F
authors.initials: LF
authors.lastname: Brass
authors.forename: Scott L
authors.initials: SL
authors.lastname: Diamond
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism / Q000494:pharmacology; D001792:Blood Platelets / Q000378:metabolism* / Q000648:ultrastructure; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D006706:Homeostasis / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D010716:Phosphatidylinositols / Q000378:metabolism*; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058472:Receptors, Purinergic P2Y1
chemical_list: C546382:P2RY1 protein, human; D010716:Phosphatidylinositols; D058910:Purinergic P2 Receptor Agonists; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; D000244:Adenosine Diphosphate; D002118:Calcium