Myotonic dystrophy protein kinase phosphorylates phospholamban and regulates calcium uptake in cardiomyocyte sarcoplasmic reticulum.
Myotonic dystrophy (DM) is caused by a CTG expansion in the 3'-untranslated region of a protein kinase gene (DMPK). Cardiovascular disease is one of the most prevalent causes of death in DM patients. Electrophysiological studies in cardiac muscles from DM patients and from DMPK(-/-) mice suggested that DMPK is critical to the modulation of cardiac contractility and to the maintenance of proper cardiac conduction activity. However, there are no data regarding the molecular signaling pathways involved in DM heart failure. Here we show that DMPK expression in cardiac myocytes is highly enriched in the sarcoplasmic reticulum (SR) where it colocalizes with the ryanodine receptor and phospholamban (PLN), a muscle-specific SR Ca(2+)-ATPase (SERCA2a) inhibitor. Coimmunoprecipitation studies showed that DMPK and PLN can physically associate. Furthermore, purified wild-type DMPK, but not a kinase-deficient mutant (K110A DMPK), phosphorylates PLN in vitro. Subsequent studies using the DMPK(-/-) mice demonstrated that PLN is hypo-phosphorylated in SR vesicles from DMPK(-/-) mice compared with wild-type mice both in vitro and in vivo. Finally, we show that Ca(2+) uptake in SR is impaired in ventricular homogenates from DMPK(-/-) mice. Together, our data suggest the existence of a novel regulatory DMPK pathway for cardiac contractility and provide a molecular mechanism for DM heart pathology.
Kaliman
Perla
P
Institute of Molecular Medicine, University of California, San Diego, California 92093, USA. p.kaliman@ub.edu
Catalucci
Daniele
D
Lam
Jason T
JT
Kondo
Richard
R
Gutiérrez
José Carlos Paz
JC
Reddy
Sita
S
Palacín
Manuel
M
Zorzano
Antonio
A
Chien
Kenneth R
KR
Ruiz-Lozano
Pilar
P
D000256:Adenoviridae / Q000378:metabolism; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D006367:HeLa Cells; D006352:Heart Ventricles / Q000473:pathology; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D017403:In Situ Hybridization; D051379:Mice; D008822:Mice, Transgenic; D008856:Microscopy, Fluorescence; D009154:Mutation; D032383:Myocytes, Cardiac / Q000378:metabolism*; D065636:Myotonin-Protein Kinase; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D019837:Ryanodine Receptor Calcium Release Channel / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D019076:Transgenes; D000099211:Phospholamban
D000911:Antibodies, Monoclonal; D002118:Calcium; D002135:Calcium-Binding Proteins; D000252:Calcium-Transporting ATPases; D018076:DNA, Complementary; D065636:Myotonin-Protein Kinase; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D019837:Ryanodine Receptor Calcium Release Channel; D053498:Sarcoplasmic Reticulum Calcium-Transporting ATPases; D000099211:Phospholamban; C585517:DMPK protein, human; C585516:DMPK protein, mouse