Spectrin proteins spring into action to restore nucleus

June 20, 2017 by Samantha Jamison
Credit: Carnegie Mellon University College of Engineering

When you lift weights, carry heavy boxes, or engage in physical activity, the cells in your body stretch and deform to accommodate your movements. But how do your cells recover, or return to their original state, once you set down the weights, unpack those heavy boxes, or complete your workout?

Carnegie Mellon University's Associate Professor of Chemical Engineering Kris Dahl and Chemical Engineering Ph.D. student Travis Armiger discovered that the cell's nucleus recovers from major deformations (e.g. muscle cells or bone cells that stretch during exercise) in part because of a spring-like, mechanical element that exists in the nucleus. This mechanical element, called a spectrin protein, helps transform the nucleus back into its original shape after the cell endures a period of high stress.

Before Dahl and Armiger completed their study, most scientists understood that spectrin proteins increased the elasticity of erythrocytes (), regulated membrane stability in the cytoskeleton of nucleated cells, and helped repair damage to the cell's DNA.

In general, most scientists hypothesize that spectrin proteins help maintain the structure of the cell's nucleus, but they have not hypothesized how spectrin proteins might affect the mechanics of the cell's nucleus.  Through their study, Dahl and Armiger confirm that spectrin proteins do in fact contribute to the resiliency of the cell's nucleus.

Carnegie Mellon University's Associate Professor of Chemical Engineering Kris Dahl explains her lab's discovery of the protein spectrin, which allows cell nuclei to deform and bounce back without being damaged. Credit: Carnegie Mellon University College of Engineering

"What's understood about nuclear mechanics is that there's a stiff nucleoskeleton primarily composed of lamina proteins … which as a whole, are able to deform and squeeze through spaces [in the body]," says Armiger.

"What we've shown is that there are other proteins present in the nucleoskeleton called spectrin proteins that act like springs … and help pull the nucleus back to its original shape [after deformation]."

The nucleus contains most of the cell's genetic material in thread-like strands called chromosomes. These chromosomes also encompass portions of the human genome, or the complete set of genetic information that ultimately builds an organism, allowing it to grow and develop over time.

The genome is surrounded by a flexible shell called the nucleoskeleton, which sits along the inside of the nuclear-membrane, protecting the nucleus from permanent damage or deformation. As cells squeeze through small pathways in the body, the nucleus tends to deform. But the existence of lamina (stiff proteins that compose the nucleoskeleton), allow the nucleus to deform without rupturing. If the lamina prevent the nucleus from rupturing, then what exactly helps the nucleus return to its original shape?

Carnegie Mellon University's graduate student Travis Armiger demonstrates how spectrin proteins allow a cell nucleus to deform and bounce back. Credit: Carnegie Mellon University College of Engineering

"Lamin filaments are able to bend and come back [to their original shape]," says Dahl. "However, they form a network structure, and when they're in a network structure, they don't deform that easily, even though the nucleus does deform. So it [the nucleus] will crinkle, but it does need a spring to be able to pop back into its nuclear shape." 

The discovery of the spring-like spectrin protein is important because scientists can now understand how the cell's recovers after major bouts of deformation. The existence of spectrin explains how an individual's muscle cells contract after lifting weights or how their cardiovascular cells respond to increased blood pressure. Scientists may also link spectrin to different muscular dystrophy diseases such as Emery-Dreifuss muscular dystrophy.

"We find this [discovery] interesting because these discoveries come from the most interesting directions," said Dahl. "We were investigating a usually found in blood . Our studies were performed in a cancer cell line. And the implications are for . This happens in science all of the time: by allowing yourself to think outside the box and follow through with rigorous study, you can make the greatest discoveries."

Dahl and Armiger's research was published in volume 49 of Elsevier's Journal of Biomechanics.

Explore further: Molecular structure of the cell nucleoskeleton revealed for the first time

More information: Travis J. Armiger et al, Nuclear mechanical resilience but not stiffness is modulated by ?II-spectrin, Journal of Biomechanics (2016). DOI: 10.1016/j.jbiomech.2016.10.034

Related Stories

Researchers discover new cell structures

June 28, 2006

Carnegie Mellon University researchers Kris Noel Dahl and Mohammad F. Islam have made a new breakthrough for children suffering from an extremely rare disease that accelerates the aging process by about seven times the normal ...

How cell nuclei squeeze into tight spaces

August 22, 2016

As cells move throughout our bodies, they often have to squeeze through tight nooks and crannies in their environment, reliably springing back to their original shape. The structures involved in this process are still a mystery, ...

Study reveals how HIV enters cell nucleus

June 21, 2016

Loyola University Chicago scientists have solved a mystery that has long baffled HIV researchers: How does HIV manage to enter the nucleus of immune system cells?

Putting the squeeze on a cell's nucleus

June 16, 2015

Nuclear membranes protect genes—life's most precious cargo—but little is known about why they function in different tissue types. For instance, nuclei in brain cells tend to be soft and pliable while those in bone cells ...

Ghost Protein Leaves Fresh Tracks in the Cell

October 30, 2006

Spectrin and ankyrin are two essential proteins acting like bricks and mortar to shape and fortify cell membranes. But distinguishing which protein is the brick and which is the mortar has turned out to be difficult. New ...

Recommended for you

New discovery challenges long-held evolutionary theory

October 19, 2017

Monash scientists involved in one of the world's longest evolution experiments have debunked an established theory with a study that provides a 'high-resolution' view of the molecular details of adaptation.

Water striders illustrate evolutionary processes

October 19, 2017

How do new species arise and diversify in nature? Natural selection offers an explanation, but the genetic and environmental conditions behind this mechanism are still poorly understood. A team led by Abderrahman Khila at ...

Gene editing in the brain gets a major upgrade

October 19, 2017

Genome editing technologies have revolutionized biomedical science, providing a fast and easy way to modify genes. However, the technique allowing scientists to carryout the most precise edits, doesn't work in cells that ...

Gut bacteria from wild mice boost health in lab mice

October 19, 2017

Laboratory mice that are given the gut bacteria of wild mice can survive a deadly flu virus infection and fight colorectal cancer dramatically better than laboratory mice with their own gut bacteria, researchers report October ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.