A Restrictive Cardiomyopathy Mutation in an Invariant Proline at the Myosin Head/Rod Junction Enhances Head Flexibility and Function, Yielding Muscle Defects in Drosophila.
An "invariant proline" separates the myosin S1 head from its S2 tail and is proposed to be critical for orienting S1 during its interaction with actin, a process that leads to muscle contraction. Mutation of the invariant proline to leucine (P838L) caused dominant restrictive cardiomyopathy in a pediatric patient (Karam et al., Congenit. Heart Dis. 3:138-43, 2008). Here, we use Drosophila melanogaster to model this mutation and dissect its effects on the biochemical and biophysical properties of myosin, as well as on the structure and physiology of skeletal and cardiac muscles. P838L mutant myosin isolated from indirect flight muscles of transgenic Drosophila showed elevated ATPase and actin sliding velocity in vitro. Furthermore, the mutant heads exhibited increased rotational flexibility, and there was an increase in the average angle between the two heads. Indirect flight muscle myofibril assembly was minimally affected in mutant homozygotes, and isolated fibers displayed normal mechanical properties. However, myofibrils degraded during aging, correlating with reduced flight abilities. In contrast, hearts from homozygotes and heterozygotes showed normal morphology, myofibrillar arrays, and contractile parameters. When P838L was placed in trans to Mhc(5), an allele known to cause cardiac restriction in flies, it did not yield the constricted phenotype. Overall, our studies suggest that increased rotational flexibility of myosin S1 enhances myosin ATPase and actin sliding. Moreover, instability of P838L myofibrils leads to decreased function during aging of Drosophila skeletal muscle, but not cardiac muscle, despite the strong evolutionary conservation of the P838 residue.
Biology Department, Molecular Biology Institute, Heart Institute, San Diego State University, San Diego, CA 92182-4614, USA.
Madhulika
M
Achal
Biology Department, Molecular Biology Institute, Heart Institute, San Diego State University, San Diego, CA 92182-4614, USA.
Adriana S
AS
Trujillo
Biology Department, Molecular Biology Institute, Heart Institute, San Diego State University, San Diego, CA 92182-4614, USA.
Girish C
GC
Melkani
Department of Biological Sciences, University of Massachusetts, Lowell, MA 01854, USA.
Gerrie P
GP
Farman
Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA.
Karen
K
Ocorr
Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD 21205, USA.
Meera C
MC
Viswanathan
Department of Bioengineering, University of California, San Diego, La Jolla, CA 92093, USA.
Gaurav
G
Kaushik
Department of Biological Sciences and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180-3590, USA.
Christopher S
CS
Newhard
Department of Biological Sciences and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180-3590, USA.
Bernadette M
BM
Glasheen
Biology Department, Molecular Biology Institute, Heart Institute, San Diego State University, San Diego, CA 92182-4614, USA.
Anju
A
Melkani
Biology Department, Molecular Biology Institute, Heart Institute, San Diego State University, San Diego, CA 92182-4614, USA.
Jennifer A
JA
Suggs
Department of Biological Sciences, University of Massachusetts, Lowell, MA 01854, USA.
Jeffrey R
JR
Moore
Department of Biological Sciences and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, NY 12180-3590, USA.
Douglas M
DM
Swank
Development, Aging and Regeneration Program, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA 92037, USA.
Rolf
R
Bodmer
Department of Medicine, Division of Cardiology, Johns Hopkins University, Baltimore, MD 21205, USA.
Anthony
A
Cammarato
Biology Department, Molecular Biology Institute, Heart Institute, San Diego State University, San Diego, CA 92182-4614, USA. Electronic address: sbernstein@mail.sdsu.edu.
Sanford I
SI
Bernstein
D000199:Actins / Q000235:genetics; D000818:Animals; D002313:Cardiomyopathy, Restrictive / Q000235:genetics*; D004331:Drosophila melanogaster / Q000235:genetics* / Q000378:metabolism; D005426:Flight, Animal / Q000502:physiology; D009119:Muscle Contraction / Q000235:genetics; D018482:Muscle, Skeletal / Q000378:metabolism; D009154:Mutation / Q000235:genetics*; D009206:Myocardium / Q000378:metabolism; D009210:Myofibrils / Q000235:genetics; D018995:Myosin Heavy Chains / Q000235:genetics; D015879:Myosin Subfragments / Q000235:genetics*; D009218:Myosins / Q000235:genetics; D010641:Phenotype; D011392:Proline / Q000235:genetics*
D000199:Actins; D015879:Myosin Subfragments; D011392:Proline; D018995:Myosin Heavy Chains; D009218:Myosins
Drosophila melanogaster; contraction; electron microscopy; motility; myofibril