Small Molecule RPI-194 Stabilizes Activated Troponin to Increase the Calcium Sensitivity of Striated Muscle Contraction
Small molecule cardiac troponin activators could potentially enhance cardiac muscle contraction in the treatment of systolic heart failure. We designed a small molecule, RPI-194, to bind cardiac/slow skeletal muscle troponin (Cardiac muscle and slow skeletal muscle share a common isoform of the trop...
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| Format: | Article |
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Frontiers Media S.A.
2022-06-01
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| Series: | Frontiers in Physiology |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fphys.2022.892979/full |
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| author | Zabed Mahmud Svetlana Tikunova Natalya Belevych Cory S. Wagg Pavel Zhabyeyev Philip B. Liu David V. Rasicci Christopher M. Yengo Gavin Y. Oudit Gary D. Lopaschuk Peter J. Reiser Jonathan P. Davis Peter M. Hwang Peter M. Hwang |
| author_facet | Zabed Mahmud Svetlana Tikunova Natalya Belevych Cory S. Wagg Pavel Zhabyeyev Philip B. Liu David V. Rasicci Christopher M. Yengo Gavin Y. Oudit Gary D. Lopaschuk Peter J. Reiser Jonathan P. Davis Peter M. Hwang Peter M. Hwang |
| author_sort | Zabed Mahmud |
| collection | DOAJ |
| description | Small molecule cardiac troponin activators could potentially enhance cardiac muscle contraction in the treatment of systolic heart failure. We designed a small molecule, RPI-194, to bind cardiac/slow skeletal muscle troponin (Cardiac muscle and slow skeletal muscle share a common isoform of the troponin C subunit.) Using solution NMR and stopped flow fluorescence spectroscopy, we determined that RPI-194 binds to cardiac troponin with a dissociation constant KD of 6–24 μM, stabilizing the activated complex between troponin C and the switch region of troponin I. The interaction between RPI-194 and troponin C is weak (KD 311 μM) in the absence of the switch region. RPI-194 acts as a calcium sensitizer, shifting the pCa50 of isometric contraction from 6.28 to 6.99 in mouse slow skeletal muscle fibers and from 5.68 to 5.96 in skinned cardiac trabeculae at 100 μM concentration. There is also some cross-reactivity with fast skeletal muscle fibers (pCa50 increases from 6.27 to 6.52). In the slack test performed on the same skinned skeletal muscle fibers, RPI-194 slowed the velocity of unloaded shortening at saturating calcium concentrations, suggesting that it slows the rate of actin-myosin cross-bridge cycling under these conditions. However, RPI-194 had no effect on the ATPase activity of purified actin-myosin. In isolated unloaded mouse cardiomyocytes, RPI-194 markedly decreased the velocity and amplitude of contractions. In contrast, cardiac function was preserved in mouse isolated perfused working hearts. In summary, the novel troponin activator RPI-194 acts as a calcium sensitizer in all striated muscle types. Surprisingly, it also slows the velocity of unloaded contraction, but the cause and significance of this is uncertain at this time. RPI-194 represents a new class of non-specific troponin activator that could potentially be used either to enhance cardiac muscle contractility in the setting of systolic heart failure or to enhance skeletal muscle contraction in neuromuscular disorders. |
| first_indexed | 2024-04-13T21:19:31Z |
| format | Article |
| id | doaj.art-756603ce756d47d9bebb8a3a2a2a53cd |
| institution | Directory Open Access Journal |
| issn | 1664-042X |
| language | English |
| last_indexed | 2024-04-13T21:19:31Z |
| publishDate | 2022-06-01 |
| publisher | Frontiers Media S.A. |
| record_format | Article |
| series | Frontiers in Physiology |
| spelling | doaj.art-756603ce756d47d9bebb8a3a2a2a53cd2022-12-22T02:29:33ZengFrontiers Media S.A.Frontiers in Physiology1664-042X2022-06-011310.3389/fphys.2022.892979892979Small Molecule RPI-194 Stabilizes Activated Troponin to Increase the Calcium Sensitivity of Striated Muscle ContractionZabed Mahmud0Svetlana Tikunova1Natalya Belevych2Cory S. Wagg3Pavel Zhabyeyev4Philip B. Liu5David V. Rasicci6Christopher M. Yengo7Gavin Y. Oudit8Gary D. Lopaschuk9Peter J. Reiser10Jonathan P. Davis11Peter M. Hwang12Peter M. Hwang13Department of Biochemistry, University of Alberta, Edmonton, AB, CanadaDepartment of Physiology and Cell Biology, The Ohio State University, Columbus, OH, United StatesDivision of Biosciences, College of Dentistry, The Ohio State University, Columbus, OH, United StatesDepartment of Pediatrics, University of Alberta, Edmonton, AB, CanadaDepartment of Medicine, University of Alberta, Edmonton, AB, CanadaDepartment of Medicine, University of Alberta, Edmonton, AB, CanadaDepartment of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, University Park, PA, United StatesDepartment of Cellular and Molecular Physiology, College of Medicine, Pennsylvania State University, University Park, PA, United StatesDepartment of Medicine, University of Alberta, Edmonton, AB, CanadaDepartment of Pediatrics, University of Alberta, Edmonton, AB, CanadaDivision of Biosciences, College of Dentistry, The Ohio State University, Columbus, OH, United StatesDepartment of Physiology and Cell Biology, The Ohio State University, Columbus, OH, United StatesDepartment of Biochemistry, University of Alberta, Edmonton, AB, CanadaDepartment of Medicine, University of Alberta, Edmonton, AB, CanadaSmall molecule cardiac troponin activators could potentially enhance cardiac muscle contraction in the treatment of systolic heart failure. We designed a small molecule, RPI-194, to bind cardiac/slow skeletal muscle troponin (Cardiac muscle and slow skeletal muscle share a common isoform of the troponin C subunit.) Using solution NMR and stopped flow fluorescence spectroscopy, we determined that RPI-194 binds to cardiac troponin with a dissociation constant KD of 6–24 μM, stabilizing the activated complex between troponin C and the switch region of troponin I. The interaction between RPI-194 and troponin C is weak (KD 311 μM) in the absence of the switch region. RPI-194 acts as a calcium sensitizer, shifting the pCa50 of isometric contraction from 6.28 to 6.99 in mouse slow skeletal muscle fibers and from 5.68 to 5.96 in skinned cardiac trabeculae at 100 μM concentration. There is also some cross-reactivity with fast skeletal muscle fibers (pCa50 increases from 6.27 to 6.52). In the slack test performed on the same skinned skeletal muscle fibers, RPI-194 slowed the velocity of unloaded shortening at saturating calcium concentrations, suggesting that it slows the rate of actin-myosin cross-bridge cycling under these conditions. However, RPI-194 had no effect on the ATPase activity of purified actin-myosin. In isolated unloaded mouse cardiomyocytes, RPI-194 markedly decreased the velocity and amplitude of contractions. In contrast, cardiac function was preserved in mouse isolated perfused working hearts. In summary, the novel troponin activator RPI-194 acts as a calcium sensitizer in all striated muscle types. Surprisingly, it also slows the velocity of unloaded contraction, but the cause and significance of this is uncertain at this time. RPI-194 represents a new class of non-specific troponin activator that could potentially be used either to enhance cardiac muscle contractility in the setting of systolic heart failure or to enhance skeletal muscle contraction in neuromuscular disorders.https://www.frontiersin.org/articles/10.3389/fphys.2022.892979/fullcardiac troponin activatorcalcium sensitizerinotropesystolic heart failurestriated musclethin filament |
| spellingShingle | Zabed Mahmud Svetlana Tikunova Natalya Belevych Cory S. Wagg Pavel Zhabyeyev Philip B. Liu David V. Rasicci Christopher M. Yengo Gavin Y. Oudit Gary D. Lopaschuk Peter J. Reiser Jonathan P. Davis Peter M. Hwang Peter M. Hwang Small Molecule RPI-194 Stabilizes Activated Troponin to Increase the Calcium Sensitivity of Striated Muscle Contraction Frontiers in Physiology cardiac troponin activator calcium sensitizer inotrope systolic heart failure striated muscle thin filament |
| title | Small Molecule RPI-194 Stabilizes Activated Troponin to Increase the Calcium Sensitivity of Striated Muscle Contraction |
| title_full | Small Molecule RPI-194 Stabilizes Activated Troponin to Increase the Calcium Sensitivity of Striated Muscle Contraction |
| title_fullStr | Small Molecule RPI-194 Stabilizes Activated Troponin to Increase the Calcium Sensitivity of Striated Muscle Contraction |
| title_full_unstemmed | Small Molecule RPI-194 Stabilizes Activated Troponin to Increase the Calcium Sensitivity of Striated Muscle Contraction |
| title_short | Small Molecule RPI-194 Stabilizes Activated Troponin to Increase the Calcium Sensitivity of Striated Muscle Contraction |
| title_sort | small molecule rpi 194 stabilizes activated troponin to increase the calcium sensitivity of striated muscle contraction |
| topic | cardiac troponin activator calcium sensitizer inotrope systolic heart failure striated muscle thin filament |
| url | https://www.frontiersin.org/articles/10.3389/fphys.2022.892979/full |
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