The Ca2+/calmodulin‐dependent kinase kinase β‐AMP‐activated protein kinase‐α1 pathway regulates phosphorylation of cytoskeletal targets in thrombin‐stimulated human platelets

Abstract

See also Randriamboavonjy V, Fleming I. Energy and motion: AMPKa1 and its role in platelet activation. This issue, pp 970-2.Summary. Background: Platelet activation requires sweeping morphologic changes, supported by contraction and remodeling of the platelet actin cytoskeleton. In various other cell types, AMP-activated protein kinase (AMPK) controls the phosphorylation state of cytoskeletal targets. Objective: To determine whether AMPK is activated during platelet aggregation and contributes to the control of cytoskeletal targets. Results: We found that AMPK-a1 was mainly activated by thrombin, and not by other platelet agonists, in purified human platelets. Thrombin activated AMPK-a1 ex vivo via a Ca 2+ / calmodulin-dependent kinase kinase b (CaMKKb)-dependent pathway. Pharmacologic inhibition of CaMKKb blocked thrombin-induced platelet aggregation and counteracted thrombin-induced phosphorylation of several cytoskeletal proteins, namely, regulatory myosin light chains (MLCs), cofilin, and vasodilator-stimulated phosphoprotein (VASP), three key elements involved in actin cytoskeletal contraction and polymerization. Platelets isolated from mice lacking AMPK-a1 showed reduced aggregation in response to thrombin, and this was associated with defects in MLC, cofilin and VASP phosphorylation and actin polymerization. More importantly, we show, for the first time, that the AMPK pathway is activated in platelets of patients undergoing major cardiac surgery, in a heparin-sensitive manner. Conclusion: AMPK-a1 is activated by thrombin in human platelets. It controls the phosphorylation of key cytoskeletal targets and actin cytoskeletal remodeling during platelet aggregation.

AMPK activation by glucagon-like peptide-1 prevents NADPH oxidase activation induced by hyperglycemia in adult cardiomyocytes

“…GLP-1 binding to its receptor could trigger a Gq signaling event leading to AMPK activation. A Gq-coupled receptor has indeed already been reported (20,31). We can speculate that an increase in calcium concentration after GLP-1 stimulates CaMKK-␤, which, in turn, activates AMPK.…”

Long-Acting Anticoagulant Rodenticide (Superwarfarin) Poisoning: A Review of Its Historical Development, Epidemiology, and Clinical Management

“…Long-acting anticoagulant rodenticide poisoning, however, contradicts this dictum as it is most frequently associated with mucocutaneous (or, platelet-type) bleeding. It is well known that thrombin plays a key role in platelet activation and it has been observed that LAAR-associated bleeding is closely associated with the depletion of thrombin (FII) [21,51,[87][88][89].…”

Energy and motion: AMP‐activated protein kinase α1 and its role in platelet activation

“…However, the latter is likely to be an oversimplification, and is not a universally observed phenomenon. Onselaer et al [8] reported that the thrombin-induced aggregation of human platelets was associated with the CAMKKb-dependent phosphorylation of several cytoskeletal proteins, including myosin light chain, cofilin, and vasodilator-stimulated phosphoprotein (VASP). The authors also reported that platelets from AMPKa1…”

“…Clearly, it is difficult to exclude the possibility that other factors affected AMPK activation and ACC phosphorylation under these conditions. Although the work of Onslaer et al [8] clearly highlights the potential importance of AMPK signaling in platelet function, their work also leaves several questions unanswered. For example, the authors' observation that the CAMKKb-AMPKa1 pathway could only be activated by thrombin is more than unexpected.…”

“…Onslaer et al suggest that the discrepancy between their study and the previous one could be related to the incubation time, as inhibition was only seen when STO-690 was incubated for a very short period (2 min). It should be noted, however, that Onslaer et al [8] used a buffer containing prostaglandin E 1 during platelet isolation to prevent aggregation. This is relevant because prostaglandin E 1 has marked effects on thrombin-induced platelet aggregation and the platelet phosphoproteome, including the myosin light chain [19] and VASP [20].…”