The Lethocerus indicus, more commonly known as the Thai water bug, may be popular as a fried delicacy in Thailand, but researchers say the humble insect has a lot to teach about human muscles, particularly that of the heart's.
In fact, for a study published in the journal Science Advances, Kenneth Taylor and colleagues turned to the Thai water bug to learn more about how the heart muscles work and why sometimes they fail, gaining a better understanding of cardiomyopathy, a disease that affects the heart muscle.
Why The Thai Water Bug?
Earlier works saw that the muscles the insect uses for flight beats rhythmically with mammalian hearts. Mutations that lead to heart disease have been identified before but they are hard to study in mammals. Given the discovery of the filament, mutations altering myosin function can be explored further. Myosin mutations are problematic because even the slightest one can have a cumulative effect on how heart muscles contract.
Using an electron microscope, the researchers captured the first-ever 3D image of a tiny strand or filament of a crucial muscle the Thai water bug uses in flying. This muscle is made of a protein known as myosin, which is responsible for providing the needed power for it to contract. For the first time, individual molecules in the muscle filament were shown in a relaxed state, which is important when the muscle is re-extending.
"The image answers a whole lot of questions about myosin filaments that scientists have been wondering about for decades," said Taylor.
Thanks to the new image they captured, the researchers are now able to observe how molecular motors function, seeing how they are arranged to keep actin filaments from re-extending muscles. Additionally, they were able to get a look at myosin rods appearing "like a bamboo forest."
Muscle Function And Heart Disease
Muscles have two filament types: myosin and actin. They mostly differ in that myosin filaments have two parts: a very long rod and a molecular motor. Numerous, the rods form the backbone of the muscle filament. During contraction, molecular motors grab on to the muscles' actin filaments, resulting in muscle shortening. This process is accompanied by a certain force, and myosin rods have to be strong enough to withstand it.
Understanding muscle filaments better, particularly the myosin ones, is important in addressing cardiomyopathy because a third of mutations in myosin filaments that lead to the disease occur within the rods. According to Taylor, many cardiomyopathy mutations may be understood by thinking of them as problems in muscle relaxation.
Hoping their work leads to novel cardiomyopathy treatments in the future, the researchers are now working to boost resolution in the filament images to get a better look at amino acids individually and get a better grasp of how they interact with each other.
The study received funding support from the American Heart Association and the National Institutes of Health, and also included research work from Robert Edwards, Michael Reedy, Dianne Taylor and Zhongjun Hu.
Photo: Day Donaldson | Flickr
