Functional Consequences of a Mutation in an Expressed Human α-Cardiac Actin at a Site Implicated in Familial Hypertrophic Cardiomyopathy

Bookwalter, Carol S.; Trybus, Kathleen M.

doi:10.1074/jbc.m512935200

Cited by 61 publications

(62 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The acto-S1 docking model (50) suggests that Arg-95 of actin is involved in the interaction with myosin, and previous mutational studies suggest that negative charges in this region are important for myosin binding (48,(51)(52)(53). Consistent with this, R95C filaments, in which the net negative charge is increased in the region, showed greater affinity for myosin in in vitro motility assays.…”

Section: Velocitysupporting

confidence: 70%

Dominant Negative Mutant Actins Identified in Flightless Drosophila Can Be Classified into Three Classes

Noguchi

Gomibuchi

Murakami

et al. 2010

Journal of Biological Chemistry

View full text Add to dashboard Cite

Strongly dominant negative mutant actins, identified by An and Mogami (An, H. S., and Mogami, K. (1996) J. Mol. Biol. 260, 492-505), in the indirect flight muscle of Drosophila impaired its flight, even when three copies of the wild-type gene were present. Understanding how these strongly dominant negative mutant actins disrupt the function of wild-type actin would provide useful information about the molecular mechanism by which actin functions in vivo. Here, we expressed and purified six of these strongly dominant negative mutant actins in Dictyostelium and classified them into three groups based on their biochemical phenotypes. The first group, G156D, G156S, and G268D actins, showed impaired polymerization and a tendency to aggregate under conditions favoring polymerization. G63D actin of the second group was also unable to polymerize but, unlike those in the first group, remained soluble under polymerizing conditions. Kinetic analyses using G63D actin or G63D actin⅐gelsolin complexes suggested that the pointed end surface is defective, which would alter the polymerization kinetics of wild-type actin when mixed and could affect formation of thin filament structures in indirect flight muscle. The third group, R95C and E226K actins, was normal in terms of polymerization, but their motility on heavy meromyosin surfaces in the presence of tropomyosin-troponin indicated altered sensitivity to Ca 2؉ . Cofilaments in which R95C or E226K actins were copolymerized with a 3-fold excess of wild-type actin also showed altered Ca 2؉ sensitivity in the presence of tropomyosin-troponin.Actin filaments are major components of the cytoskeletons of all eukaryotic cells and play key roles in a variety of cellular functions, including cell migration, organelle transport, and muscle contraction. These diverse processes depend on the dynamic nature of actin filaments and their interactions with various actin-binding proteins (1), which are thought to involve conformational changes in the subunits that make up actin filaments. For instance, the stability of actin filaments is affected by the conformational difference between actin subunits carrying ATP or ADP and those that do not (2, 3), whereas cofilin, a major actin filament severing protein, alters the twist of actin filaments (4). In addition, modification of actin filaments through chemical cross-linking causes motility defects with myosin, suggesting a possible link between actin-myosin interaction and the conformational dynamics of actin (5, 6). Moreover, the myosin-induced conformational changes appear to be cooperative (7-9), e.g. Ca 2ϩ -triggered conformational changes in the skeletal muscle actin filaments are enhanced by cooperative conformational changes induced by myosin (10). In many cases, however, details of the molecular relationship between conformational changes in actin and its physiological function remain unclear.Actin is a highly conserved protein, so that Dictyostelium actin 15 shares 91% amino acid identity with rabbit skeletal muscle actin. This implies ...

show abstract

Section: Velocitysupporting

confidence: 70%

Dominant Negative Mutant Actins Identified in Flightless Drosophila Can Be Classified into Three Classes

Noguchi

Gomibuchi

Murakami

et al. 2010

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…This study also revealed reduced thin filament cooperativity; this may influence Ca 2ϩ sensitivity under some conditions, although our previous analysis of tropomyosin DCM mutations found no connection between cooperativity and phenotype (23). Studies on the kinetics of baculovirus-expressed E99K actin-activated myosin S-1-ATPase show that the K m is 4-fold greater than wild type, indicating a weakening of the weak binding interaction between actin and myosin⅐ADP⅐P i (45). This was interpreted as leading to lower force production, but we found the maximum developed pressure in ACTC E99K hearts was not different from nontransgenic mice.…”

Section: Actc E99k Mouse Model Of Hcm-we Developed Thementioning

confidence: 99%

Molecular Mechanism of the E99K Mutation in Cardiac Actin (ACTC Gene) That Causes Apical Hypertrophy in Man and Mouse

Song

Dyer

Stuckey

et al. 2011

Journal of Biological Chemistry

View full text Add to dashboard Cite

We generated a transgenic mouse model expressing the apical hypertrophic cardiomyopathy-causing mutation ACTC E99K at 50% of total heart actin and compared it with actin from patients carrying the same mutation. The actin mutation caused a higher Ca 2؉ sensitivity in reconstituted thin filaments measured by in vitro motility assay (2.3-fold for mice and 1.3-fold for humans) and in skinned papillary muscle. The mutation also abolished the change in Ca 2؉ sensitivity normally linked to troponin I phosphorylation. MyBP-C and troponin I phosphorylation levels were the same as controls in transgenic mice and human carrier heart samples. ACTC E99K mice exhibited a high death rate between 28 and 45 days (48% females and 22% males). At 21 weeks, the hearts of the male survivors had enlarged atria, increased interstitial fibrosis, and sarcomere disarray. MRI showed hypertrophy, predominantly at the apex of the heart. End-diastolic volume and end-diastolic pressure were increased, and relaxation rates were reduced compared with nontransgenic littermates. End-systolic pressures and volumes were unaltered. ECG abnormalities were present, and the contractile response to ␤-adrenergic stimulation was much reduced. Older mice (29-week-old females and 38-week-old males) developed dilated cardiomyopathy with increased end-systolic volume and continuing increased end-diastolic pressure and slower contraction and relaxation rates. ECG showed atrial flutter and frequent atrial ectopic beats at rest in some ACTC E99K mice. We propose that the ACTC E99K mutation causes higher myofibrillar Ca 2؉ sensitivity that is responsible for the sudden cardiac death, apical hypertrophy, and subsequent development of heart failure in humans and mice.

show abstract

“…Other actin mutations within myosin binding domains (e.g., A331P and A295S) are associated with HCM. One actin HCM mutation (E99K) has been evaluated in vitro by a series of biochemical assays, which demonstrated a weakened interaction with myosin and reduced force production (73). Several other actin mutations have been expressed in vitro and found to demonstrate variable defects in protein folding which correlated with impaired incorporation into the cytoskeleton of mammalian (noncardiac) cell lines (919).…”

Section: Actinmentioning

confidence: 99%

Designing Heart Performance by Gene Transfer

Davis¹,

Westfall²,

Townsend³

et al. 2008

Physiological Reviews

View full text Add to dashboard Cite

The birth of molecular cardiology can be traced to the development and implementation of high-fidelity genetic approaches for manipulating the heart. Recombinant viral vector-based technology offers a highly effective approach to genetically engineer cardiac muscle in vitro and in vivo. This review highlights discoveries made in cardiac muscle physiology through the use of targeted viral-mediated genetic modification. Here the history of cardiac gene transfer technology and the strengths and limitations of viral and nonviral vectors for gene delivery are reviewed. A comprehensive account is given of the application of gene transfer technology for studying key cardiac muscle targets including Ca2+handling, the sarcomere, the cytoskeleton, and signaling molecules and their posttranslational modifications. The primary objective of this review is to provide a thorough analysis of gene transfer studies for understanding cardiac physiology in health and disease. By comparing results obtained from gene transfer with those obtained from transgenesis and biophysical and biochemical methodologies, this review provides a global view of cardiac structure-function with an eye towards future areas of research. The data presented here serve as a basis for discovery of new therapeutic targets for remediation of acquired and inherited cardiac diseases.

show abstract

Functional Consequences of a Mutation in an Expressed Human α-Cardiac Actin at a Site Implicated in Familial Hypertrophic Cardiomyopathy

Cited by 61 publications

References 34 publications

Dominant Negative Mutant Actins Identified in Flightless Drosophila Can Be Classified into Three Classes

Dominant Negative Mutant Actins Identified in Flightless Drosophila Can Be Classified into Three Classes

Molecular Mechanism of the E99K Mutation in Cardiac Actin (ACTC Gene) That Causes Apical Hypertrophy in Man and Mouse

Designing Heart Performance by Gene Transfer

Contact Info

Product

Resources

About