Scientists obtain clearer view of how eye lens proteins are sorted

Nov 03, 2009

New research reveals how proteins that are critical for the transparency of the eye lens are properly sorted and localized in membrane bilayers. The study, published by Cell Press in the November 3rd issue of Biophysical Journal, analyzes how interactions between lipid and protein molecules can selectively concentrate proteins in certain regions of the cell membrane.

All cells are surrounded by a dynamic semi-permeable structure called the plasma membrane. Cell plasma membranes are made of a thin bilayer of lipids interspersed with a diverse complement of proteins. Research has shown that the lipids and proteins are not randomly distributed across the plasma membrane. Instead, functional microdomains or "rafts" are enriched for certain lipids and proteins. Although raft sequestration of many classes of lipids and proteins has been extensively studied, mechanisms for sorting proteins that span the membrane to form channels are not as well understood.

Dr. Thomas J.McIntosh from the Department of Cell Biology at Duke University Medical Center and his colleagues were interested in examining whether the plasma membrane distribution of the major channel proteins depends on how they are sorted between raft and non-raft microdomains. "We already knew that lens cell plasma membranes contain high concentrations of the raft lipids cholesterol and sphingomyelin, and that rafts form in lens membranes," says Dr. McIntosh. "In addition, we knew that lens channel proteins, connexins and aquaporin, are preferentially located in different regions of lens cell plasma membranes."

Using both detergent extraction and confocal microscopy to analyze reconstituted membranes, the researchers discovered that lens connexins were primarily located in non-raft domains. In contrast, the microdomain location of aquaporin depended on its aggregation status, which was controlled by the protein: lipid ration in the membrane. Specifically, under conditions where aquaporin molecules are known to cluster together (homo-oligomerize), aquaporin was enriched in non-raft domains.

"Our observation that sequestration of aquaporin into raft microdomains was markedly increased under conditions where homo-oligomerization was observed supports the theory that clustering might modify microdomain sorting," offers Dr. McIntosh. "Taken together, our data suggest that protein-lipid interactions, as modified by aquaporin homo-oligomerization, can be a key factor in the sorting of proteins in cell membranes."

Source: Cell Press (news : web)

Explore further: Bacterial immune system has a better memory than expected

add to favorites email to friend print save as pdf

Related Stories

Chemists get grip on slippery lipids

Aug 30, 2007

The ability of the body's cells to correctly receive and convey signals is crucial to good health. Lipids, or fats, play a critical role in this regulation by providing spaces for proteins to gather and network. They are ...

How neuronal activity leads to Alzheimer's protein cleavage

Oct 20, 2008

Amyloid precursor protein (APP), whose cleavage product, amyloid-b (Ab), builds up into fibrous plaques in the brains of Alzheimer's disease patients, jumps from one specialized membrane microdomain to another to be cleaved, ...

Recommended for you

Researchers develop new model of cellular movement

2 hours ago

(Phys.org) —Cell movement plays an important role in a host of biological functions from embryonic development to repairing wounded tissue. It also enables cancer cells to break free from their sites of ...

For resetting circadian rhythms, neural cooperation is key

22 hours ago

Fruit flies are pretty predictable when it comes to scheduling their days, with peaks of activity at dawn and dusk and rest times in between. Now, researchers reporting in the Cell Press journal Cell Reports on April 17th h ...

Rapid and accurate mRNA detection in plant tissues

23 hours ago

Gene expression is the process whereby the genetic information of DNA is used to manufacture functional products, such as proteins, which have numerous different functions in living organisms. Messenger RNA (mRNA) serves ...

User comments : 0

More news stories

Researchers develop new model of cellular movement

(Phys.org) —Cell movement plays an important role in a host of biological functions from embryonic development to repairing wounded tissue. It also enables cancer cells to break free from their sites of ...

Scientists tether lionfish to Cayman reefs

Research done by U.S. scientists in the Cayman Islands suggests that native predators can be trained to gobble up invasive lionfish that colonize regional reefs and voraciously prey on juvenile marine creatures.