Scientists identify key protein behind heart's 'metronome'

Date: Feb-23-2015An 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 News Today 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.

Written by Catharine Paddock PhD

Courtesy: Medical News Today Note: Any medical information available in this news section is not intended as a substitute for informed medical advice and you should not take any action before consulting with a health care professional.