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Palmiter, Kimberly A.; Tyska, Matthew J.; Haeberle, Joe R.; Alpert, Norman R.; Fananapazir, Lameh; Warshaw, David M.

doi:10.1023/a:1005678905119

Cited by 125 publications

(51 citation statements)

References 48 publications

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“…Do the various myosin mutations differentially impact myosin performance to account for such dramatically different clinical phenotypes associated with DCM and HCM? HCM-causing mutations, especially the R403Q mutant, enhance rather than compromise function (10,15,19,28,29). Direct comparison of the mutant myosins described here with data obtained by our laboratories from mutant R403Q myosin isolated from a mouse model using all of the identical assays (29) demonstrates that V actin , F avg , and actomyosin ATPase activity all are enhanced for R403Q myosin compared with controls.…”

Section: Resultsmentioning

confidence: 59%

“…Direct comparison of the mutant myosins described here with data obtained by our laboratories from mutant R403Q myosin isolated from a mouse model using all of the identical assays (29) demonstrates that V actin , F avg , and actomyosin ATPase activity all are enhanced for R403Q myosin compared with controls. The enhanced function was also seen in myosin obtained from human ␤-cardiac samples (15,27), suggesting that the mutation has its effects regardless of the myosin backbone.…”

Section: Resultsmentioning

confidence: 95%

“…The remaining decrease in V actin may be explained by the 24% longer duration of attachment observed in the laser trap (Table 3). However, in the laser trap, where 10 M MgATP is used to enhance detection of individual events, t on is determined by both the rate of MgADP release and subsequent binding of MgATP (14,15), whereas V actin at saturating [MgATP] is limited only by the rate of ADP release (14). Therefore, the individual kinetic step(s) affected by the mutation cannot be delineated.…”

Section: Resultsmentioning

confidence: 99%

“…This mini-isolation procedure, used extensively in our laboratory (15,29,38), yields Ϸ0.2 mg of highly purified whole myosin without evidence of protein contaminants or proteolysis. Additionally, before an experiment, the myosin was further purified by centrifugation in the presence of equimolar actin and 0.001 M ATP in myosin buffer (15). By using only the supernatant, denatured ''rigor-like'' myosin that would have dramatic impeding effects in the motility assay and laser trap was eliminated.…”

Section: )mentioning

confidence: 99%

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Cardiac myosin missense mutations cause dilated cardiomyopathy in mouse models and depress molecular motor function

Schmitt

Debold²,

Ahmad³

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

108

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Dilated cardiomyopathy (DCM) leads to heart failure, a leading cause of death in industrialized nations. Approximately 30% of DCM cases are genetic in origin, with some resulting from point mutations in cardiac myosin, the molecular motor of the heart. The effects of these mutations on myosin's molecular mechanics have not been determined. We have engineered two murine models characterizing the physiological, cellular, and molecular effects of DCM-causing missense mutations (S532P and F764L) in the ␣-cardiac myosin heavy chain and compared them with WT mice. Mutant mice developed morphological and functional characteristics of DCM consistent with the human phenotypes. Contractile function of isolated myocytes was depressed and preceded left ventricular dilation and reduced fractional shortening. In an in vitro motility assay, both mutant cardiac myosins exhibited a reduced ability to translocate actin (V actin) but had similar force-generating capacities. Actin-activated ATPase activities were also reduced. Single-molecule laser trap experiments revealed that the lower V actin in the S532P mutant was due to a reduced ability of the motor to generate a step displacement and an alteration of the kinetics of its chemomechanical cycle. These results suggest that the depressed molecular function in cardiac myosin may initiate the events that cause the heart to remodel and become pathologically dilated.animal models ͉ biophysics ͉ genetics ͉ single molecule ͉ laser trap D ilated cardiomyopathy (DCM) is an early step in the pathway leading to heart failure, the leading cause of human morbidity and mortality (1, 2). Although etiological factors such as ischemia and diabetes can result in DCM, at least 30% of cases are genetic in origin, with mutations found in sarcomeric proteins associated with the cytoskeletal and contractile systems (3). Clinically, DCM is characterized by myocardial hypertrophy, thin-walled ventricles, and myocyte hypoplasia (2, 4). Dilated hearts are hypocontractile, with systolic dysfunction leading to a reduced ejection fraction: a hallmark of a failing heart (2, 3). Only recently have autosomal dominant missense mutations to the ␤-cardiac myosin heavy chain (MHC) been identified that result in DCM (5, 6). Because the primary defect resides within the heart's molecular motor, we hypothesized that altered cardiac contractile function in DCM hearts might reflect changes in the mutant myosin's ability to generate force and motion as it cyclically interacts with actin during its hydrolysis of ATP.To investigate the impact of two distinct DCM-causing MHC mutations (S532P and F764L) on cardiac myosin's molecular performance, we have genetically engineered these missense mutations separately into the murine ␣-cardiac MHC gene, the human ␤-MHC homolog, to generate two separate DCM knockin mouse models. In addition to cardiac dilation and dysfunction, defects in isolated myocyte contractility were observed that are consistent with DCM. Interestingly, defects at the whole-heart and cellular levels were cor...

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Section: Resultsmentioning

confidence: 59%

Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 99%

Section: )mentioning

confidence: 99%

See 2 more Smart Citations

Cardiac myosin missense mutations cause dilated cardiomyopathy in mouse models and depress molecular motor function

Schmitt

Debold²,

Ahmad³

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

108

View full text Add to dashboard Cite

show abstract

“…This observation emphasizes the importance of understanding the mechanisms that underlie cardiac hypercontractility caused by MHC and cMyBPC mutations, and how these functional defects can be reversed or normalized using genetic or pharmacological approaches 12. Missense mutations in human cardiac β‐MHC result in variable effects on contractile function including reduced13, 14 or enhanced intrinsic force generation15, 16; decreased14, 16 or enhanced15 myosin ATPase activity; and accelerated13, 15, 17 or slowed16 actin sliding velocities. Importantly, recent data show that HCM‐causing mutations in β‐MHC that cause hypercontractility weaken myosin's S1‐S2 intradomain interactions, thus effectively increasing the total number of myosin heads that can interact with actin during systole,11 thereby chronically elevating left ventricular ejection fraction 5, 18.…”

Section: Introductionmentioning

confidence: 99%

Impact of the Myosin Modulator Mavacamten on Force Generation and Cross‐Bridge Behavior in a Murine Model of Hypercontractility

Mamidi

Doh

et al. 2018

JAHA

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BackgroundRecent studies suggest that mavacamten (Myk461), a small myosin‐binding molecule, decreases hypercontractility in myocardium expressing hypertrophic cardiomyopathy‐causing missense mutations in myosin heavy chain. However, the predominant feature of most mutations in cardiac myosin binding protein‐C (cMyBPC) that cause hypertrophic cardiomyopathy is reduced total cMyBPC expression, and the impact of Myk461 on cMyBPC‐deficient myocardium is currently unknown.Methods and ResultsWe measured the impact of Myk461 on steady‐state and dynamic cross‐bridge (XB) behavior in detergent‐skinned mouse wild‐type myocardium and myocardium lacking cMyBPC (knockout (KO)). KO myocardium exhibited hypercontractile XB behavior as indicated by significant accelerations in rates of XB detachment (krel) and recruitment (kdf) at submaximal Ca2+ activations. Incubation of KO and wild‐type myocardium with Myk461 resulted in a dose‐dependent force depression, and this impact was more pronounced at low Ca2+ activations. Interestingly, Myk461‐induced force depressions were less pronounced in KO myocardium, especially at low Ca2+ activations, which may be because of increased acto‐myosin XB formation and potential disruption of super‐relaxed XBs in KO myocardium. Additionally, Myk461 slowed krel in KO myocardium but not in wild‐type myocardium, indicating increased XB “on” time. Furthermore, the greater degree of Myk461‐induced slowing in kdf and reduction in XB recruitment magnitude in KO myocardium normalized the XB behavior back to wild‐type levels.ConclusionsThis is the first study to demonstrate that Myk461‐induced force depressions are modulated by cMyBPC expression levels in the sarcomere, and emphasizes that clinical use of Myk461 may need to be optimized based on the molecular trigger that underlies the hypertrophic cardiomyopathy phenotype.

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Hypertrophic Cardiomyopathy

Marian¹

2007

Cardiovascular Genetics and Genomics for the Cardiologist

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Cited by 125 publications

References 48 publications

Cardiac myosin missense mutations cause dilated cardiomyopathy in mouse models and depress molecular motor function

Cardiac myosin missense mutations cause dilated cardiomyopathy in mouse models and depress molecular motor function

Impact of the Myosin Modulator Mavacamten on Force Generation and Cross‐Bridge Behavior in a Murine Model of Hypercontractility

Hypertrophic Cardiomyopathy

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