Piecing Together the Protein Puzzle

Proteins are the key to understanding almost all of our biological functions. How they’re made, how they’re folded, where they come from, where they go, and how they’re regulated – all of these are vital components of a healthy body, and we’re only just beginning to generate a clear picture of how these processes interact. Researchers from around the world are focused on finding out more, and two groups – one from New York City and another from Heidelberg – have developed new methods of doing just that.

Researchers at Albert Einstein College of Medicine (New York, NY, USA) have devised a new fluorescence microscopy technique that, for the first time, allows the visualization of proteins as they are translated. Until now, it’s been impossible to say with certainty exactly where and when in the cell messenger RNAs are translated into proteins – an insight critical for studying the molecular basis of protein diseases like Alzheimer’s. Along with collaborators at the European Molecular Biology Laboratory (EMBL) in Heidelberg, the Albert Einstein group devised a new method that takes advantage of a crucial aspect of translation: the removal of RNA binding proteins from mRNA to allow ribosomes to attach. The researchers labeled the mRNA molecules in red and the binding proteins in green, so that complexes with both appear yellow. When ribosomes attach to these mRNAs, they displace the green-labeled binding proteins so that the “naked” mRNA only possesses the red fluorescence (see Figure 1). The technique is called TRICK, or Translating RNA Imaging by Coat protein Knockoff. Using TRICK, the EMBL researchers were able to confirm the time and place of translation of a particular Drosophila protein, oskar (1) – something never previously known.

TRICK isn’t the only new protein imaging technique on the block, though. Another group at EMBL have recently developed a novel approach to fluorescence correlation spectroscopy (FCS) that allows scientists to track the movements and meetings of individual proteins in a cell after they’ve been fused to a fluorescent marker. Though FCS technology has been around since the early 1970s, the instruments are cumbersome to operate manually and the data are difficult to interpret. The new technique automates both the measurement of protein behavior and the analysis of the resulting large amounts of data (2), leading to huge time savings – while a researcher might take a day to look at a single protein in a few cells, the automated approach can look at tens of proteins in thousands of cells in the same timeframe. This ability to treat FCS as a high-throughput method, says principal investigator Jan Ellenberg, “is key to studying biological networks that typically consist of tens to hundreds of components.” The group’s next step? To assemble a “Google map” of all the proteins in a living cell.

Despite leaps and bounds in microscopic technologies over recent years, much of what occurs inside a single cell remains a mystery to us. With new methods like these that give us the ability to look at the life of a protein, from its translation to its journey around the cell, we can gain new insights into human health and disease at every level.