Cell membranes: Synthetics save time and cut costs

Jul 03, 2013
Cell membranes: Synthetics save time and cut costs
Proteins for drug screening can now be isolated using a cell-free approach developed at A*STAR. Credit: iStockphoto/Thinkstock

Screening for critical drug targets known as G-protein-coupled receptors (GPCRs) is now possible without the need to extract these proteins from their native cells. Extraction requires the use of stabilizing lipids, which damage the structural integrity and functionality of GPCRs. The cell-free approach was developed by Madhavan Nallani from the A*STAR Institute of Materials Research and Engineering, Singapore, along with co-workers in Singapore, Germany and Austria.

Nallani and co-workers focused on GPCRs because they are ideal that pass through cell membranes. These proteins are involved in , cell adhesion and , as well as major illnesses, including hypertension and diabetes.

The team's approach produced GPCRs directly in artificial cell-like pockets called polymersomes. "This [approach] circumvents the tedious protein isolation process and the use of lipids or detergents as stabilizing agents," says Nallani.

As a proof of concept, the researchers synthesized the GPCR dopamine receptor D2 in vitro in the presence of polymersomes and the DNA that encodes for the protein. "This cell- provides an easy way to produce proteins directly from their DNA," notes Nallani. The proteins generated by transcription and translation became incorporated into the polymer-based membranes via spontaneous self-assembly.

Characterization using fluorescently labeled antibodies that are receptor-specific showed that the self-assembled product displayed stronger fluorescence than the unmodified polymersomes, confirming the insertion of the receptor. This characterization also indicated that the membrane-incorporated portion of the receptor was properly oriented in the polymersomes.

This video is not supported by your browser at this time.
Artificial cell membranes are easy-to-handle mimics of real cell membranes that could transform drug discovery. Credit: 2013 A*STAR Institute of Materials Research and Engineering

Nallani's team further investigated the structure of the polymersome-inserted receptor using a fluorescently tagged dopamine. "Dopamine will bind only if the receptor is correctly folded and oriented," explains Nallani. After incubation, the GPCR-modified polymersomes showed higher fluorescence than the negative controls, indicating that the receptor maintained its structural integrity upon insertion into the polymersome.

The researchers assessed the potential use of the GPCR-modified polymersomes for drug screening and biosensing by synthesizing the receptor in the presence of polymersomes, which they patterned onto glass surfaces. Incubation of the resulting material with fluorescently labeled dopamine illuminated the patterns—proof of a successful GPCR addition. Exposure of these fluorescent patterns to increasing concentrations of unlabeled dopamine caused the fluorescence to decrease, showing that dopamine displaced the fluorescent ligand.

"We are developing this technology through a commercialization project from the A*STAR Exploit Technologies Pte Ltd and focusing on small-molecule and antibody screening," says Nallani. His team is planning to form a start-up company with this approach within the next few months.

Explore further: Team finds dissimilar proteins evolved similar 7-part shape

More information: May, S., et al. In vitro expressed GPCR inserted in polymersome membranes for ligand-binding studies. Angewandte Chemie International Edition 52, 749–753 (2013). onlinelibrary.wiley.com/doi/10.1002/anie.201204645/abstract

add to favorites email to friend print save as pdf

Related Stories

Finding a family for a pair of orphan receptors in the brain

May 21, 2013

Researchers at Emory University have identified a protein that stimulates a pair of "orphan receptors" found in the brain, solving a long-standing biological puzzle and possibly leading to future treatments for neurological ...

Recommended for you

Breakthrough points to new drugs from nature

Apr 16, 2014

Researchers at Griffith University's Eskitis Institute have developed a new technique for discovering natural compounds which could form the basis of novel therapeutic drugs.

World's first successful visualisation of key coenzyme

Apr 16, 2014

Japanese researchers have successfully developed the world's first imaging method for visualising the behaviour of nicotine-adenine dinucleotide derivative (NAD(P)H), a key coenzyme, inside cells. This feat ...

User comments : 0

More news stories

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...