27 June 2005: Protein synthesis under the spotlight

US chemists have developed a technique for investigating protein synthesis using light-responsive ’caged compounds’. The technique enables the study of protein synthesis in small, defined regions of a cell at specific times, and its developers predict it will be useful for investigating nerve cell metabolism.

Caged compounds are often used to study cellular processes. They comprise a bioactive molecule, such as a neurotransmitter, that is linked via a covalent bond to a light-sensitive compound known as a chromophore, which prevents the bioactive molecule from working. Shining ultraviolet (UV) light onto the caged compound cleaves the bond, releasing the bioactive molecule. 

Most research has concentrated on creating caged compounds with bioactive molecules that stimulate cellular processes. But researchers studying protein synthesis at the Universityof Georgia, Athens, and the California Institute of Technology (Caltech), Pasadena, have created a caged compound that incorporates a biological inhibitor.

They selected a caged compound comprising the antibiotic anisomycin, which inhibits protein synthesis by blocking the formation of peptide bonds, and a chromophore known as Bhc-Aniso. 

The chemists tested the compound in ovary cells, nerve cells and a cell line known as HEK293, all of which had been engineered to express green fluorescent protein (GFP). 

Brief flashes of UV light - designed to activate the protein-synthesis inhibitor - were sufficient to inhibit GFP-generated fluorescence in all the cells, the researchers report. Inhibition occurred almost instantaneously and was limited to within 100?m of the centre of the UV light beam.

’Ultimately, we want to understand the role local protein synthesis plays in biological systems such as neurons,’ explained co-lead researcher Erin Schuman at Caltech. ’When and where in the neuron is protein synthesis used to bring about changes? How does protein synthesis regulate synaptic strength and axonal outgrowth? These are questions we’d like to answer.’ Jon Evans