In a study published in the Journal Of Clinical Investigation, scientists reported the discovery of the role of a family of proteins called Popeye. According to researchers these proteins have an important role in determining how exactly the heart is responding to stress. This new study can represent a first towards developing new therapies for cardiac arrhythmias.
This new family of proteins (also known as Popdc) was discovered ten years ago when it was observed that they are present in high quantities in muscular fibers, reason for why they were named Popeye. Until now, the exact functions of this proteins was unknown, but this study reveals their function and that is to increase and to sustain the heart rhythm when are they are stimulated by adrenaline (hormone that is released in stressful periods). For this study, researchers used mice that presented Popdc protein deficiency.
Physiologically, the response of heart’s dominant peacemaker to adrenaline is to increase beat rhythm thus making the heart beat faster in order to ensure a proper amount of oxygen needed in stressful circumstances. In mice with low levels of Popdc proteins the heart rhythm began to decline as a response to adrenaline secretion.
This response – decreased heart rhythm when stressed is commonly encountered in the elderly and could indicate a sign of sinus node disease, a condition which is properly treated by implantation of an artificial pacemaker. Scientists have concluded their results could represent the first step in finding new treatment options for patients suffering from sinus node disease as well as others arrhythmias such as atrial fibrillation or sudden cardiac death.
Researchers also observed that Popdc proteins are located on the pacemaker cells of the heart, in the outer membrane. Pacemaker cells are responsible for cardiac automatism (the propriety of the heart to self-stimulate and to beat with a certain rate). When adrenalin is secreted, Popdc proteins increase their production of cAMP, a signalling molecule which has the capacity to modify the electrical proprieties of the cell membrane, making the heart beat faster. It is now believed that this is the actual way in which the heart rate is influenced by adrenaline secretion.
Scientists pointed out this study shows only the mechanism by which the heart adapts to stress, but the exact mechanism according to which adrenaline acts on cardiac cells is not fully understood. Maybe in the future they will be able to elucidate this mechanism and to discover new treatment options for cardiac arrhythmias induced by stress.