title: Platelet secretion is kinetically heterogeneous in an agonist-responsive manner.
abstract: Platelets release numerous bioactive molecules stored in their granules enabling them to exert a wide range of effects on the vascular microenvironment. Are these granule cargo released thematically in a context-specific pattern or via a stochastic, kinetically controlled process? Here we sought to describe the platelet exocytosis using a systematic examination of platelet secretion kinetics. Platelets were stimulated for increasing times with different agonists (ie, thrombin, PAR1-agonist, PAR4-agonist, and convulxin) and micro-ELISA arrays were used to quantify the release of 28 distinct α-granule cargo molecules. Agonist potency directly correlated with the speed and extent of release. PAR4-agonist induced slower release of fewer molecules, whereas thrombin rapidly induced the greatest release. Cargo with opposing actions (eg, proangiogenic and antiangiogenic) had similar release profiles, suggesting limited thematic response to specific agonists. From the release time-course data, rate constants were calculated and used to probe for underlying patterns. Probability density function and operator variance analyses were consistent with 3 classes of release events, differing in their rates. The distribution of cargo into these 3 classes was heterogeneous, suggesting that platelet secretion is a stochastic process potentially controlled by several factors, such as cargo solubility, granule shape, and/or granule-plasma membrane fusion routes.
authors.affiliation: Department of Molecular and Cellular Biochemistry, University of Kentucky College of Medicine, Lexington, KY 40536, USA.
authors.forename: Deepa
authors.initials: D
authors.lastname: Jonnalagadda
authors.forename: Leighton T
authors.initials: LT
authors.lastname: Izu
authors.forename: Sidney W
authors.initials: SW
authors.lastname: Whiteheart
mesh_terms: D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D003435:Crotalid Venoms / Q000494:pharmacology; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D006801:Humans; D007700:Kinetics; D037181:Lectins, C-Type; D008297:Male; D010978:Platelet Factor 4 / Q000378:metabolism; D040081:Protein Array Analysis / Q000379:methods; D044463:Receptor, PAR-1 / Q000819:agonists*; D018179:Receptors, Thrombin / Q000819:agonists*; D055571:Secretory Pathway / Q000187:drug effects; D022142:Secretory Vesicles / Q000187:drug effects / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism; D013917:Thrombin / Q000494:pharmacology*; D001619:beta-N-Acetylhexosaminidases / Q000378:metabolism
chemical_list: D003435:Crotalid Venoms; D037181:Lectins, C-Type; D044463:Receptor, PAR-1; D018179:Receptors, Thrombin; D012701:Serotonin; C028890:convulxin; D010978:Platelet Factor 4; D001619:beta-N-Acetylhexosaminidases; D013917:Thrombin; C112908:protease-activated receptor 4