Abstract
The shortening of sarcomeres that co-ordinates the pump function of the heart is stimulated by electrically-mediated increases in [Ca2+]. This process of excitation-contraction coupling (ECC) is subject to modulation by neurohormonal mediators that tune the output of the heart to meet the needs of the organism. Endothelin-1 (ET-1) is a potent modulator of cardiac function with effects on contraction amplitude, chronotropy and automaticity. The actions of ET-1 are evident during normal adaptive physiological responses and increased under pathophysiological conditions, such as following myocardial infarction and during heart failure, where ET-1 levels are elevated. In myocytes, ET-1 acts through ETA- or ETB-G protein-coupled receptors (GPCRs). Although well studied in atrial myocytes, the influence and mechanisms of action of ET-1 upon ECC in ventricular myocytes are not fully resolved. We show in rat ventricular myocytes that ET-1 elicits a biphasic effect on fractional shortening (initial transient negative and sustained positive inotropy) and increases the peak amplitude of systolic Ca2+ transients in adult rat ventricular myocytes. The negative inotropic phase was ETB receptor-dependent, whereas the positive inotropic response and increase in peak amplitude of systolic Ca2+ transients required ETA receptor engagement. Both effects of ET-1 required phospholipase C (PLC)-activity, although distinct signalling pathways downstream of PLC elicited the effects of each ET receptor. The negative inotropic response involved inositol 1,4,5-trisphosphate (InsP3) signalling and protein kinase C epsilon (PKCε). The positive inotropic action and the enhancement in Ca2+ transient amplitude induced by ET-1 were independent of InsP3 signalling, but suppressed by PKCε. Serine 302 in cardiac myosin binding protein-C was identified as a PKCε substrate that when phosphorylated contributed to the suppression of contraction and Ca2+ transients by PKCε following ET-1 stimulation. Thus, our data provide a new role and mechanism of action for InsP3 and PKCε in mediating the negative inotropic response and in restraining the positive inotropy and enhancement in Ca2+ transients following ET-1 stimulation.
Original language | English |
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Pages (from-to) | 1-18 |
Number of pages | 18 |
Journal | Journal of Molecular and Cellular Cardiology |
Volume | 117 |
DOIs | |
Publication status | Published - Apr 2018 |
Externally published | Yes |
Keywords
- Animals
- Calcium/metabolism
- Calcium Signaling/drug effects
- Cardiotonic Agents/pharmacology
- Carrier Proteins/metabolism
- Cytosol/metabolism
- Endothelin-1/pharmacology
- Excitation Contraction Coupling/drug effects
- Heart Ventricles/cytology
- Inositol 1,4,5-Trisphosphate Receptors/metabolism
- Male
- Myocardial Contraction/drug effects
- Myocytes, Cardiac/drug effects
- Phosphorylation/drug effects
- Protein Kinase C-epsilon/antagonists & inhibitors
- Rats, Wistar
- Receptors, Endothelin/metabolism
- Sarcoplasmic Reticulum/drug effects
- Type C Phospholipases/metabolism