Scientists identify key protein behind heart's 'metronome'


Scientists identify key protein behind heart's 'metronome'

An important feature of a healthy heart is its ability to maintain a steady beat. Even a slight faltering in the heart's rhythm can cause sudden death. Now, a new study identifies a key protein that helps maintain the heart's "metronome."

Over an average lifetime, the heart beats 2.5 billion times.

The average life expectancy of a human being today is about 71 years, or 2.5 billion heart beats, each precisely calibrated to maintain an astonishing, unwavering level of consistency.

Unfortunately, however, this is not the case for everyone and millions of people worldwide die every year because of problems arising from irregular heartbeat or arrhythmia.

Now, scientists have discovered how a key protein helps to maintain the mechanism behind the heart's "metronome" and hope their finding will lead to new life-saving treatments.

They found that myosin-binding protein C - known as C protein - plays a crucial role in synchronizing the contractions of heart muscle fibers.

The researchers - including W. Jonathan Lederer, professor of physiology at the University of Maryland School of Medicine in Baltimore - report their findings in the journal Science Advances.

First study to identify the key role of C protein in maintaining heart rhythm

Prof. Lederer says it appears that C protein plays a very important role in maintaining heart rhythm and they are very excited by the finding.

"We envision a lot of research that we can do with this new knowledge," he adds, "We will continue to investigate this in all kinds of ways."

The discovery of C protein's role is like finding a missing piece of a jigsaw. The other pieces were found years ago - they reveal, for example, that calcium is a trigger for the heartbeat and activates proteins that cause sarcomeres - the fibrous proteins that make up heart muscle cells - to contract.

But the new study shows that calcium is not spread evenly along the sarcomere fiber. On a beat-to-beat basis, calcium molecules are released from the ends of each sarcomere and yet the contractions are uniform. This is puzzling because you might think this can only happen if the calcium molecules are evenly spread along the fiber.

This is where C protein comes in, say the researchers. They knew from previous studies that C protein is present in all heart muscle cells, but theirs is the first to show what it does.

C protein enables synchronous sarcomere contraction by correcting for calcium

To study the physiology of C protein, the team measured calcium release and how the muscle fibers reacted mechanically to it in mice.

They found that C protein appears to exquisitely sensitize certain locations on the sarcomere to calcium, causing it to contract just as much along its length as at the ends, despite the unevenness of calcium concentration along the fiber.

In other words, C protein enables synchronous contraction in the sarcomere by correcting for the non-uniformity of calcium along its length.

The researchers conclude their study shows the presence and position of C protein in the sarcomere is critically important for normal heart function, and any disturbance in that arrangement will likely contribute to heart problems.

The team believes modifying C protein could be a way to treat arrhythmia. Prof. Lederer comments:

I think this could be very big. This protein is definitely a drug target."

The National Institutes of Health funded the study.

In January 2015, Medical-Diag.com reported an intriguing study where researchers suggested Beethoven may have suffered from irregular heartbeat because they could hear "musical arrhythmias" in some of the great composer's pieces.

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Section Issues On Medicine: Cardiology