Omecamtiv Mecarbil Enhances the Duty Ratio of Human β-Cardiac Myosin Resulting in Increased Calcium Sensitivity and Slowed Force Development in Cardiac Muscle*
| Autor: | Michael J. Previs, Anja M. Swenson, Christopher M. Fetrow, Wanjian Tang, William C. Unrath, Cheavar A. Blair, Christopher M. Yengo, Kenneth S. Campbell |
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| Jazyk: | angličtina |
| Rok vydání: | 2017 |
| Předmět: |
0301 basic medicine
Population chemistry.chemical_element macromolecular substances Calcium Myosins Biochemistry Mass Spectrometry Ventricular Myosins 03 medical and health sciences Myosin head chemistry.chemical_compound Mice Protein Domains Myosin medicine Animals Humans Urea education Molecular Biology Actin education.field_of_study Dose-Response Relationship Drug Chemistry Myocardium Cardiac muscle Cell Biology Actomyosin Actins Recombinant Proteins Adenosine Diphosphate Omecamtiv mecarbil Adenosine diphosphate Kinetics 030104 developmental biology medicine.anatomical_structure Biophysics Stress Mechanical Molecular Biophysics |
| Popis: | The small molecule drug omecamtiv mecarbil (OM) specifically targets cardiac muscle myosin and is known to enhance cardiac muscle performance, yet its impact on human cardiac myosin motor function is unclear. We expressed and purified human β-cardiac myosin subfragment 1 (M2β-S1) containing a C-terminal Avi tag. We demonstrate that the maximum actin-activated ATPase activity of M2β-S1 is slowed more than 4-fold in the presence of OM, whereas the actin concentration required for half-maximal ATPase was reduced dramatically (30-fold). We find OM does not change the overall actin affinity. Transient kinetic experiments suggest that there are two kinetic pathways in the presence of OM. The dominant pathway results in a slow transition between actomyosin·ADP states and increases the time myosin is strongly bound to actin. However, OM also traps a population of myosin heads in a weak actin affinity state with slow product release. We demonstrate that OM can reduce the actin sliding velocity more than 100-fold in the in vitro motility assay. The ionic strength dependence of in vitro motility suggests the inhibition may be at least partially due to drag forces from weakly attached myosin heads. OM causes an increase in duty ratio examined in the motility assay. Experiments with permeabilized human myocardium demonstrate that OM increases calcium sensitivity and slows force development (ktr) in a concentration-dependent manner, whereas the maximally activated force is unchanged. We propose that OM increases the myosin duty ratio, which results in enhanced calcium sensitivity but slower force development in human myocardium. |
| Databáze: | OpenAIRE |
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