Plasmin activity promotes amyloid deposition in a transgenic model of human transthyretin amyloidosis

Ivana Slamova,Diana Canetti,Philip N Hawkins,Janet A Gilbertson,Riccardo Porcari,J Paul Simons,Glenys A Tennent,Nigel Rendell,Julian D Gillmore,Graham W Taylor,Guglielmo Verona,Mark B Pepys,P Patrizia Mangione,Rozita Adib,Nicola Botcher,Raya Al-Shawi,Stephan Ellmerich,Vittorio Bellotti,Michal R Golos

doi:10.1038/s41467-021-27416-z

Abstract

Cardiac ATTR amyloidosis, a serious but much under-diagnosed form of cardiomyopathy, is caused by deposition of amyloid fibrils derived from the plasma protein transthyretin (TTR), but its pathogenesis is poorly understood and informative in vivo models have proved elusive. Here we report the generation of a mouse model of cardiac ATTR amyloidosis with transgenic expression of human TTRS52P. The model is characterised by substantial ATTR amyloid deposits in the heart and tongue. The amyloid fibrils contain both full-length human TTR protomers and the residue 49-127 cleavage fragment which are present in ATTR amyloidosis patients. Urokinase-type plasminogen activator (uPA) and plasmin are abundant within the cardiac and lingual amyloid deposits, which contain marked serine protease activity; knockout of α2-antiplasmin, the physiological inhibitor of plasmin, enhances amyloid formation. Together, these findings indicate that cardiac ATTR amyloid deposition involves local uPA-mediated generation of plasmin and cleavage of TTR, consistent with the previously described mechano-enzymatic hypothesis for cardiac ATTR amyloid formation. This experimental model of ATTR cardiomyopathy has potential to allow further investigations of the factors that influence human ATTR amyloid deposition and the development of new treatments.

Highlights

Cardiac ATTR amyloidosis, a serious but much under-diagnosed form of cardiomyopathy, is caused by deposition of amyloid fibrils derived from the plasma protein transthyretin (TTR), but its pathogenesis is poorly understood and informative in vivo models have proved elusive
We confirm the dependence of amyloidogenesis on both fibril seeding and proteolytic cleavage of TTR, identify amyloid deposits as sites of abnormal proteolytic activity, and show that plasmin activity promotes ATTR amyloid deposition in vivo
To test directly whether plasmin activity contributes to the formation of ATTR amyloid in vivo, we evaluated the effect of knockout of the specific plasmin inhibitor α2-antiplasmin (Serpinf2) on ATTR amyloid deposition

Summary

Introduction

Cardiac ATTR amyloidosis, a serious but much under-diagnosed form of cardiomyopathy, is caused by deposition of amyloid fibrils derived from the plasma protein transthyretin (TTR), but its pathogenesis is poorly understood and informative in vivo models have proved elusive. Urokinase-type plasminogen activator (uPA) and plasmin are abundant within the cardiac and lingual amyloid deposits, which contain marked serine protease activity; knockout of α2-antiplasmin, the physiological inhibitor of plasmin, enhances amyloid formation Together, these findings indicate that cardiac ATTR amyloid deposition involves local uPAmediated generation of plasmin and cleavage of TTR, consistent with the previously described mechano-enzymatic hypothesis for cardiac ATTR amyloid formation. Remarkable advances in cardiac magnetic resonance imaging[13] and repurposing of radionuclide bone tracers that yield highly characteristic images[14,15] enable reliable non-invasive diagnosis[16] of cardiac ATTR amyloidosis without recourse to heart biopsy, and have revealed that the prevalence of ATTR cardiomyopathy is substantial, especially in older men[17,18] In contrast to these diagnostic advances, quality of life remains poor, survival short and development of treatment is in its infancy[17]. We confirm the dependence of amyloidogenesis on both fibril seeding and proteolytic cleavage of TTR, identify amyloid deposits as sites of abnormal proteolytic activity, and show that plasmin activity promotes ATTR amyloid deposition in vivo

Methods

Results

Conclusion