Featured Research

from universities, journals, and other organizations

'Modus Operandi' Of Heart Muscle Protein Discovered

Date:
April 14, 2008
Source:
University of Pennsylvania School of Medicine
Summary:
Researchers have discovered that a protein called leiomodin promotes the assembly of an important heart muscle protein called actin. What's more, Lmod directs the assembly of actin to form the pumping unit of the heart.

Researchers at the University of Pennsylvania School of Medicine have discovered that a protein called leiomodin (Lmod) promotes the assembly of an important heart muscle protein called actin. What's more, Lmod directs the assembly of actin to form the pumping unit of the heart. The findings appear in this week's issue of Science.

"Very little was known about Lmod when we began this study," says lead author Roberto Dominguez, PhD, Associate Professor of Physiology.

"It appeared that this protein was present in muscle cells but this had not been demonstrated directly and nobody knew what it did," explains Dominguez. "We compared the amino acid sequence of Lmod with the sequence of another protein called tropomodulin [Tmod] that was already known to bind actin filaments in muscle cells. We found that one part of Lmod was very similar to Tmod, but Lmod was a bigger protein than Tmod and contained unique features that made us suspect that it could assemble the actin filaments of the heart muscle. This is exactly what we found."

The results answer a question that scientists studying the heart have long asked: What controls the assembly of the pumping unit of the heart?

Actin is the most abundant protein in most animal cells and forms long polymers, or filaments, that make up the cell skeleton. In the cells that make up muscles and the heart, interactions of actin filaments with motor proteins produce the contractions that pump blood through the body.

Actin spontaneously forms polymers in test tubes, but living cells use nucleator proteins to control the time and place where actin filaments forms. "For a long time, physiologists have wondered what serves as the nucleator protein in cardiac muscle cells," says co-author Professor Thomas Pollard, PhD, of Yale University. "It was very satisfying after all these years to discover that Lmod can serve as the nucleator protein to initiate the forming of actin polymers in heart muscle cells."

Lmod also directs actin filaments to the sarcomere, the part of the heart that controls contractions or pumping. When Lmod was knocked down in cardiac muscle cells by an RNA silencing technique, the sarcomeres became completely disorganized and could not direct muscles to contract.

Proper localization of Lmod in heart cells is critical, because even moderately elevated levels promote the formation of abnormal actin bundles in the nuclei of cardiac muscle cells where actin does not belong. A similar disorganization of actin bundles is characteristic of a disease of skeletal muscle weakness called intranuclear rod myopathy. Although this disease is caused by a mutation in a skeletal muscle-specific actin gene, the similarity in appearance suggests that mutations in Lmod could cause the same type of disease in cardiac muscle cells.

The Penn team is currently studying how the heart regulates the level of Lmod and how Lmod might be relevant to cardiac muscle disease. In addition, the team is attempting to crystallize Lmod in order to study its structure directly.

Malgorzata Boczkowska of Penn and David Chereau of Boston Biomedical Institute are co-first authors of this study. Other key contributors are Pekka Lappalainen and Aneta Skwarbek-Maruszewska of the University of Helsinki; Ikuko Fujiwara of Yale; David B. Hayes of Boston Biomedical Institute; and Grzegorz Rebowski of Penn. The study was supported by grants from the National Heart Lung and Blood Institute and the National Institute of General Medical Sciences.


Story Source:

The above story is based on materials provided by University of Pennsylvania School of Medicine. Note: Materials may be edited for content and length.


Cite This Page:

University of Pennsylvania School of Medicine. "'Modus Operandi' Of Heart Muscle Protein Discovered." ScienceDaily. ScienceDaily, 14 April 2008. <www.sciencedaily.com/releases/2008/04/080410153613.htm>.
University of Pennsylvania School of Medicine. (2008, April 14). 'Modus Operandi' Of Heart Muscle Protein Discovered. ScienceDaily. Retrieved July 26, 2014 from www.sciencedaily.com/releases/2008/04/080410153613.htm
University of Pennsylvania School of Medicine. "'Modus Operandi' Of Heart Muscle Protein Discovered." ScienceDaily. www.sciencedaily.com/releases/2008/04/080410153613.htm (accessed July 26, 2014).

Share This




More Health & Medicine News

Saturday, July 26, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Beatings and Addiction: Pakistan Drug 'clinic' Tortures Patients

Beatings and Addiction: Pakistan Drug 'clinic' Tortures Patients

AFP (July 24, 2014) A so-called drugs rehab 'clinic' is closed down in Pakistan after police find scores of ‘patients’ chained up alleging serial abuse. Duration 03:05 Video provided by AFP
Powered by NewsLook.com
Too Few Teens Receiving HPV Vaccination, CDC Says

Too Few Teens Receiving HPV Vaccination, CDC Says

Newsy (July 24, 2014) The Centers for Disease Control and Prevention is blaming doctors for the low number of children being vaccinated for HPV. Video provided by Newsy
Powered by NewsLook.com
New Painkiller Designed To Discourage Abuse: Will It Work?

New Painkiller Designed To Discourage Abuse: Will It Work?

Newsy (July 24, 2014) The FDA approved Targiniq ER on Wednesday, a painkiller designed to keep users from abusing it. Like any new medication, however, it has doubters. Video provided by Newsy
Powered by NewsLook.com
Doctor At Forefront Of Fighting Ebola Outbreak Gets Ebola

Doctor At Forefront Of Fighting Ebola Outbreak Gets Ebola

Newsy (July 24, 2014) Sheik Umar Khan has treated many of the people infected in the Ebola outbreak, and now he's become one of them. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins