title: Caspases 3 and 9 are translocated to the cytoskeleton and activated by thrombin in human platelets. Evidence for the involvement of PKC and the actin filament polymerization.
abstract: Platelets express, among others, initiator caspase 9 and effector caspase 3. Upon activation by physiological agonists, calcium ionophores or under shear stress they might develop apoptotic events. Although it is well known that the cytoskeletal network plays a crucial role in apoptosis, the relationship between caspases 3 and 9 and the cytoskeleton is poorly understood. Here we demonstrate that the physiological agonist thrombin is able to induce activation of caspases 3 and 9 in human platelets and significantly increases the amount in the cytoskeleton of the active forms of both caspases and the procaspases 3 and 9. After stimulation with thrombin the amount of active caspases 3 and 9 in the cytosolic and cytoskeletal fractions were significantly reduced in Ro-31-8220-treated cells, which demonstrates that caspases activation and association with the cytoskeleton needs the contribution of PKC. Inhibition of actin polymerization by cytochalasin D inhibits translocation and activation of both caspases, suggesting that thrombin stimulates caspase 3 and 9 activation and association with the reorganizing actin cytoskeleton. Finally, our results show that inhibition of thrombin-induced caspase activation has no effect on their translocation to the cytoskeleton although impairment of thrombin-evoked caspase translocation has negative effects on caspase activity, suggesting that translocation to the cytoskeleton might be important for caspase activation by thrombin in human platelets.
authors.affiliation: Unité de Recherche de Biochimie, Inst. Superieur de Biotechnologie, Monastir, Tunisia.
authors.forename: Nidhal
authors.initials: N
authors.lastname: Ben Amor
authors.forename: José A
authors.initials: JA
authors.lastname: Pariente
authors.forename: Ginés M
authors.initials: GM
authors.lastname: Salido
authors.forename: Aghleb
authors.initials: A
authors.lastname: Bartegi
authors.forename: Juan A
authors.initials: JA
authors.lastname: Rosado
mesh_terms: D008841:Actin Cytoskeleton / Q000201:enzymology*; D001704:Biopolymers; D001792:Blood Platelets / Q000187:drug effects* / Q000201:enzymology*; D053148:Caspase 3; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D015638:Cytochalasin D / Q000494:pharmacology; D003600:Cytosol / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D011493:Protein Kinase C / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D013917:Thrombin / Q000494:pharmacology*
chemical_list: D001704:Biopolymers; D061945:Caspase Inhibitors; D015638:Cytochalasin D; D011493:Protein Kinase C; D013917:Thrombin; C505407:CASP3 protein, human; C506433:CASP9 protein, human; D053148:Caspase 3; D053453:Caspase 9; D020169:Caspases