title: Ceramide-mediated depression in cardiomyocyte contractility through PKC activation and modulation of myofilament protein phosphorylation.
abstract: Although ceramide accumulation in the heart is considered a major factor in promoting apoptosis and cardiac disorders, including heart failure, lipotoxicity and ischemia-reperfusion injury, little is known about ceramide's role in mediating changes in contractility. In the present study, we measured the functional consequences of acute exposure of isolated field-stimulated adult rat cardiomyocytes to C6-ceramide. Exogenous ceramide treatment depressed the peak amplitude and the maximal velocity of shortening without altering intracellular calcium levels or kinetics. The inactive ceramide analog C6-dihydroceramide had no effect on myocyte shortening or [Ca(2+)]i transients. Experiments testing a potential role for C6-ceramide-mediated effects on activation of protein kinase C (PKC) demonstrated evidence for signaling through the calcium-independent isoform, PKCε. We employed 2-dimensional electrophoresis and anti-phospho-peptide antibodies to test whether treatment of the cardiomyocytes with C6-ceramide altered myocyte shortening via PKC-dependent phosphorylation of myofilament proteins. Compared to controls, myocytes treated with ceramide exhibited increased phosphorylation of myosin binding protein-C (cMyBP-C), specifically at Ser273 and Ser302, and troponin I (cTnI) at sites apart from Ser23/24, which could be attenuated with PKC inhibition. We conclude that the altered myofilament response to calcium resulting from multiple sites of PKC-dependent phosphorylation contributes to contractile dysfunction that is associated with cardiac diseases in which elevations in ceramides are present.
authors.affiliation: Department of Physiology and Biophysics and Center for Cardiovascular Research, College of Medicine, University of Illinois, Chicago, IL, 60612, USA.
authors.forename: Jillian N
authors.initials: JN
authors.lastname: Simon
authors.forename: Shamim A K
authors.initials: SA
authors.lastname: Chowdhury
authors.forename: Chad M
authors.initials: CM
authors.lastname: Warren
authors.forename: Sakthivel
authors.initials: S
authors.lastname: Sadayappan
authors.forename: David F
authors.initials: DF
authors.lastname: Wieczorek
authors.forename: R John
authors.initials: RJ
authors.lastname: Solaro
authors.forename: Beata M
authors.initials: BM
authors.lastname: Wolska
mesh_terms: D000818:Animals; D002518:Ceramides / Q000502:physiology*; D008297:Male; D032383:Myocytes, Cardiac / Q000502:physiology*; D009210:Myofibrils / Q000378:metabolism*; D010766:Phosphorylation; D011493:Protein Kinase C / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction
chemical_list: D002518:Ceramides; C101954:N-caproylsphingosine; D011493:Protein Kinase C