The simple ‘thump-thump, thump-thump’ rhythm of a heartbeat can be quite deceiving. With each heartbeat or cardiac cycle, the heart pumps in blood and then pushes it back out.
One half of the heart receives the deoxygenated (venous) blood used by our body and then sends it to our pulmonary system (lungs etc.) to again be enriched with oxygen. The other half of the heart receives freshly oxygenated (arterial) blood from the pulmonary system and pumps it into circulation throughout our body.
The cycle repeats throughout our lives. It is estimated that the heart beats some 35 million times in a year and more than two and a half billion times in an average lifetime without ever pausing to rest.
Each heartbeat must be precisely calibrated. One small deviation can bring sudden death.
So how does the heart pull this off?
An international team of researchers, writing in a study that was published in the inaugural issue of the journal Science Advances, have identified a specific protein called myosin-binding protein C (cMyBP-C) that they found plays a pivotal role in keeping the heart beating in reliable time.
The scientists discovered that the position of this protein within the heart’s muscle cells allows the heart’s muscle fibers to work together in perfect synchronization, which is vital to ensure the heart operates properly.
If the tiny protein should break down, the researchers found that the heart can malfunction in way that can lead to sudden death causing arrhythmias, or irregular heartbeat.
On the other hand, the researchers said their finding also suggests that making adjustments to the cMyBP-C protein could help resolve a number of heart problems and may someday be used to treat people with potentially deadly heart conditions.
Two of the study’s lead researchers, David Warshaw, Ph.D., Michael Previs, Ph.D., both molecular physiologists from the University of Vermont’s Cardiovascular Research Institute, used powerful microscopes to look inside a part of heart muscle tissue called the sarcomere.
The sarcomere, which is about one fiftieth the diameter of a human hair, expands and contracts with every heartbeat. For the heart to beat properly, trillions of these sarcomeres must contract and expand simultaneously.
“To pump blood efficiently, they all have to be doing it at the same time,” Warshaw said.
Two proteins called myosin and actin help the sarcomere expand and contract. Myosin acts like a motor that pushes or pulls the rope-like actin. In turn, actin pulls in the sarcomere and then releases it out so it can refill with blood.
Since the myosin protein is always trying to snatch and move the actin, it needs some kind of control mechanism to make sure that it’s grabbing and moving actin at the precise time when the sarcomere needs to contract.
The cMyBP-C protein, located at the center of the sarcomere, regulates the two proteins by balancing the myosin — slowing or speeding its interaction with actin as needed — to maintain the precise timing of the sarcomere’s expansion/contraction.
The researchers were able to make their findings by examining the normal heart muscle of animals. Now, the plan to find out what goes wrong with cMyBP-C protein in a diseased heart.
Once all of the research is complete, scientists then would be able to develop cMyBP-C-based pharmaceutical treatments to help repair unhealthy hearts.
Heart Beating (National Institute of Genetics, Japan)