Corporate Banner
Satellite Banner
Genomics
Scientific Community
 
Become a Member | Sign in
Home>News>This Article
  News
Return

Researchers Get Close-Up View of Water Pores Needed in the Eye's Lens

Published: Tuesday, August 06, 2013
Last Updated: Tuesday, August 06, 2013
Bookmark and Share
NIH-funded study of aquaporins could hold clues to cataract.

Researchers have achieved dynamic, atomic-scale views of a protein needed to maintain the transparency of the lens in the human eye.

The work, funded in part by the National Institutes of Health, could lead to new insights and drugs for treating cataract and a variety of other health conditions.

Aquaporin proteins form water channels between cells and are found in many tissues, but aquaporin zero (AQP0) is found only in the mammalian lens, which focuses light onto the retina, at the back of the eye.

The lens is primarily made up of unique cells called lens fibers that contain little else besides water and proteins called crystallins.

Tight packing of these fibers and of the crystallin proteins within them helps create a uniform medium that allows light to pass through the lens, almost as if it were glass.

Abnormal development or age-related changes in the lens can lead to cataract - a clouding of the lens that causes vision loss.

Besides age, other risk factors for cataract include smoking, diabetes, and genetic factors. Mutations in the AQP0 gene can cause congenital cataract and may increase the risk of age-related cataract.

"The AQP0 channel is believed to play a vital role in maintaining the transparency of the lens and in regulating water volume in the lens fibers, so understanding the molecular details of how water flows through the channel could lead to a better understanding of cataract," said Dr. Houmam Araj, who oversees programs on lens, cataract and oculomotor systems at NIH's National Eye Institute (NEI), which helped fund the research.

Closing of AQP0 channels is regulated by a calcium-sensitive protein called calmodulin, but the precise mechanism has been unclear.

Some models have suggested that calmodulin simply acts as a plug to fill the open channel. The new study, published in Nature Structural and Molecular Biology, reveals a more nuanced process in which calmodulin essentially grasps the open channel and forces it to close.

The research was a collaboration between investigators at the University of California, Irvine, and the Janelia Farm Research Campus in Ashburn, Va., a part of the Howard Hughes Medical Institute (HHMI).

Drs. James Hall and Douglas Tobias led the effort at UC Irvine. Dr. Tamir Gonen led the effort at Janelia Farm.

In prior studies, Dr. Gonen had examined the atomic structure of the AQP0 protein by X-ray crystallography, which involves crystallizing a protein and bombarding it with X-rays. But X-ray crystallography does not work well for large groups of proteins or for proteins in motion.

So in the new study, the researchers first used electron microscopy to view AQP0 and calmodulin bound together. Then they combined their microscopy and crystallography data to generate computerized models of how the two proteins interact and to identify the most critical amino acids (the building blocks for proteins) within AQP0.

To test their models, they neutralized those amino acids one by one in the actual AQP0 channel.

The AQP0 channel is made up of four identical barrel-shaped units, bundled together side by side. The researchers found that in the presence of calcium, calmodulin binds to one unit and then another, as if grabbing a pair of reins.

This makes the channel twist slightly, which causes just a few amino acids within each unit to slide into the channel's core and block the flow of water.

"Calmodulin essentially throws a molecular switch that moves in and out of the water pore, like the gate valve of a plumbing fixture," Dr. Hall said.

This new view of AQP0 could help lead to new approaches for treating cataract, Dr. Hall said. Cataracts are the most common cause of blindness worldwide.

In the United States, they affect about 1 in 6 people over age 40 and half over age 80. Congenital cataracts (present from birth) affect about 1 in 5,000 American children.

Cataracts can be successfully treated with surgery, in which the cloudy lens is removed and replaced with an artificial plastic lens. But the new findings "may be a step toward learning how to prevent or delay cataracts," said Dr. Hall.

The new findings also provide inroads to understanding how calmodulin interacts with a variety of protein channels, and thus could open doors to new drugs for other common health conditions.

In addition to aquaporins, our bodies rely on a vast menagerie of channels, many of which are regulated by calmodulin.

For example, calmodulin helps control the gating of ion channels, which allow the passage of ions (charged particles) in and out of our cells and are essential for nerve cell firing, muscle contraction, and the rhythmic beating of the heart. This study provides the first structural model of calmodulin bound to any complete protein channel.

Drs. Daniel Clemens and Steve Reichow were co-first authors on the study. NIH support for the study came from NEI (grants EY005661, EY018768), the National Institute of General Medical Sciences (NIGMS grant GM079233), a joint program on "Making Sense of Voltage Sensors" co-funded by NIGMS and the National Institute of Neurological Disorders and Stroke (grant GM086685), and the National Library of Medicine (grant LM007443).

Additional support came from HHMI, the National Science Foundation, and the German Academy of Sciences.


Further Information
Access to this exclusive content is for Technology Networks Premium members only.

Join Technology Networks Premium for free access to:

  • Exclusive articles
  • Presentations from international conferences
  • Over 2,500+ scientific posters on ePosters
  • More than 3,800+ scientific videos on LabTube
  • 35 community eNewsletters


Sign In



Forgotten your details? Click Here
If you are not a member you can join here

*Please note: By logging into TechnologyNetworks.com you agree to accept the use of cookies. To find out more about the cookies we use and how to delete them, see our privacy policy.

Related Content

Cellular Factors that Shape the 3D Landscape of the Genome Identified
Researchers have identified 50 cellular factors required for the proper 3D positioning of genes by using novel large-scale imaging technology.
Tuesday, August 18, 2015
Nuclear Process in the Brain That May Affect Disease Uncovered
Scientists have shown that the passage of molecules through the nucleus of a star-shaped brain cell, called an astrocyte, may play a critical role in health and disease.
Tuesday, August 18, 2015
Tell-tale Biomarker Detects Early Breast Cancer in NIH-funded Study
The study published online in the issue of Nature Communications.
Thursday, August 13, 2015
Scientists Adopt New Strategy to Find Huntington’s Disease Therapies
Large, international NIH-supported study uses precision medicine to tackle neurological disorders.
Tuesday, August 11, 2015
Study Shows Promise of Precision Medicine for Most Common Type of Lymphoma
The study appeared online July 20, 2015, in Nature Medicine.
Tuesday, July 21, 2015
NIH Study Identifies Gene Variant Linked to Compulsive Drinking
Mice carrying the Met68BDNF gene variant would consume excessive amounts of alcohol.
Tuesday, July 21, 2015
In Blinding Eye Disease, Trash-Collecting Cells Go Awry, Accelerate Damage
NIH research points to microglia as potential therapeutic target in retinitis pigmentosa.
Friday, July 03, 2015
Potential Therapeutic for Blinding Eye Disease
NIH research points to microglia as potential therapeutic target in retinitis pigmentosa.
Thursday, July 02, 2015
NCI-MATCH Trial will Link Targeted Cancer Drugs to Gene Abnormalities
Precision medicine trial will open to patient enrollment in July.
Tuesday, June 09, 2015
A New Role for Zebrafish: Larger Scale Gene Function Studies
A relatively new method of targeting specific DNA sequences in zebrafish could dramatically accelerate the discovery of gene function and the identification of disease genes in humans.
Monday, June 08, 2015
NIH Researchers Pilot Predictive Medicine by Studying Healthy People’s DNA
New study sequence the genomes of healthy participants to find “putative,” or presumed, mutations.
Friday, June 05, 2015
Linking Targeted Cancer Drugs to Gene Abnormalities
Investigators at the NIH have announced a series of clinical trials that will study drugs or drug combinations that target specific genetic mutations.
Wednesday, June 03, 2015
Scientists Create Mice with a Major Genetic Cause of ALS and FTD
NIH-funded study provides new platform for testing treatments for several neurodegenerative disorders.
Friday, May 22, 2015
Mice With a Major Genetic Cause of ALS and FTD Created
NIH-funded study provides new platform for testing treatments for several neurodegenerative disorders.
Thursday, May 21, 2015
New Insights into How DNA Differences Influence Gene Activity, Disease Susceptibility
NIH-funded pilot study provides a new resource about variants across the human genome.
Friday, May 08, 2015
Scientific News
Poor Survival Rates in Leukemia Linked to Persistent Genetic Mutations
For patients with an often-deadly form of leukemia, new research suggests that lingering cancer-related mutations – detected after initial treatment with chemotherapy – are associated with an increased risk of relapse and poor survival.
Searching Big Data Faster
Theoretical analysis could expand applications of accelerated searching in biology, other fields.
Growing Hepatitis C in the Lab
Recent discovery allows study of naturally occurring forms of hepatitis C virus (HCV) in the lab.
Inciting an Immune Attack on Cancer Cells
A new minimally invasive vaccine that combines cancer cells and immune-enhancing factors could be used clinically to launch a destructive attack on tumors.
Reprogramming Cancer Cells
Researchers on Mayo Clinic’s Florida campus have discovered a way to potentially reprogram cancer cells back to normalcy.
Genetic Overlapping in Multiple Autoimmune Diseases May Suggest Common Therapies
CHOP genomics expert leads analysis of genetic architecture, with eye on repurposing existing drugs.
Surprising Mechanism Behind Antibiotic-Resistant Bacteria Uncovered
Now, scientists at TSRI have discovered that the important human pathogen Staphylococcus aureus, develops resistance to this drug by “switching on” a previously uncharacterized set of genes.
How DNA ‘Proofreader’ Proteins Pick and Edit Their Reading Material
Researchers from North Carolina State University and the University of North Carolina at Chapel Hill have discovered how two important proofreader proteins know where to look for errors during DNA replication and how they work together to signal the body’s repair mechanism.
Fat in the Family?
Study could lead to therapeutics that boost metabolism.
Tissue Bank Pays Dividends for Brain Cancer Research
Checking what’s in the bank – the Brisbane Breast Bank, that is – has paid dividends for UQ cancer researchers.
Skyscraper Banner

Skyscraper Banner
Go to LabTube
Go to eposters
 
Access to the latest scientific news
Exclusive articles
Upload and share your posters on ePosters
Latest presentations and webinars
View a library of 1,800+ scientific and medical posters
2,500+ scientific and medical posters
A library of 2,500+ scientific videos on LabTube
3,800+ scientific videos
Close
Premium CrownJOIN TECHNOLOGY NETWORKS PREMIUM FREE!