Rapamycin restrains platelet procoagulant responses via FKBP-mediated protection of mitochondrial integrity

• Published in: Biochemical pharmacology 2020-07, Vol.177, p.113975-113975, Article 113975
• Main Authors: Śledź, Kamila M., Moore, Samantha F., Durrant, Tom N., Blair, Thomas A., Hunter, Roger W., Hers, Ingeborg
• Format: Article
• Language: English
• Subjects: Blood Platelets - cytology; Blood Platelets - drug effects; Blood Platelets - metabolism; Calcium Signaling - drug effects; Carrier Proteins - pharmacology; Gene Expression Regulation; Humans; Ionomycin - pharmacology; Mechanistic Target of Rapamycin Complex 1 - antagonists & inhibitors; Mechanistic Target of Rapamycin Complex 1 - genetics; Mechanistic Target of Rapamycin Complex 1 - metabolism; Mitochondria - drug effects; Mitochondria - metabolism; Morpholines - pharmacology; Peptides - pharmacology; Phosphatidylserines - metabolism; Platelet Activation - drug effects; Platelet Aggregation Inhibitors - pharmacology; Primary Cell Culture; Pyrazoles - pharmacology; Pyrimidines - pharmacology; Sirolimus - pharmacology; Tacrolimus - pharmacology; Thrombin - metabolism; Thrombin - pharmacology; TOR Serine-Threonine Kinases - antagonists & inhibitors; TOR Serine-Threonine Kinases - genetics; TOR Serine-Threonine Kinases - metabolism
• ISSN: 0006-2952; 1873-2968
• DOI: 10.1016/j.bcp.2020.113975

The graphical abstract was created using BioRender. [Display omitted] Rapamycin is a potent immunosuppressant and anti-proliferative agent used clinically to prevent organ transplant rejection and for coating coronary stents to counteract restenosis. Rapamycin complexes with the immunophilin FKBP12, which subsequently binds and inhibits mTORC1. Despite several reports demonstrating that rapamycin affects platelet-mediated responses, the underlying mechanism of how it alters platelet function is poorly characterised. This study aimed to elucidate the effect of rapamycin on platelet procoagulant responses. The effect of rapamycin on platelet activation and signalling was investigated alongside the catalytic mTOR inhibitors KU0063794 and WYE-687, and the FKBP12-binding macrolide FK506. Rapamycin affects platelet procoagulant responses by reducing externalisation of the procoagulant phospholipid phosphatidylserine, formation of balloon-like structures and local generation of thrombin. Catalytic mTOR kinase inhibitors did not alter platelet procoagulant processes, despite having a similar effect as rapamycin on Ca2+ signalling, demonstrating that the effect of rapamycin on procoagulant responses is independent of mTORC1 inhibition and not linked to a reduction in Ca2+ signalling. FK506, which also forms a complex with FKBP12 but does not target mTOR, reduced platelet procoagulant responses to a similar extent as rapamycin. Both rapamycin and FK506 prevented the loss of mitochondria integrity induced by platelet activation, one of the central regulatory events leading to PS externalisation. Rapamycin suppresses platelet procoagulant responses by protecting mitochondrial integrity in a manner independent of mTORC1 inhibition. Rapamycin and other drugs targeting FKBP immunophilins could aid the development of novel complementary anti-platelet therapies.