In an article in the September issue of Nature Chemical Biology, researchers report the use of a high-resolution imaging technique to visualize heart cell receptor clusters for the first time. The receptors that control heart rate are known to cluster into distinct signalling zones. The density of receptors in these signalling zones defines the basis of the stimulatory signal.
The heart rate is controlled by beta-adrenergic receptors located on the surface of heart cells. Adrenergic receptors belong to a class of receptor called G protein-coupled receptors, which are common in many cell types and participate in many important biological functions. Although much is known about the structures and properties of this class of receptor, little is known about the receptors' actual cellular location and distribution during cell-signalling events.
Now, Pezacki and coworkers have used a state-of-the-art microscopy technique called near-field scanning optical microscopy (NSOM) to visualize cell-surface beta-adrenergic receptors of heart cells. Because NSOM has higher resolution than conventional light microscopy, it is possible to visualize individual molecules located on the cell surface. The authors showed that between 15% and 20% of the receptors located on the cell surface were clustered into distinct groups or signalling islands. Using a combination of NSOM and fluorescence microscopy, the authors were able to estimate the density of receptors clustered in the signalling zones. Receptor stimulation produced no change in receptor density, which suggests that the receptors are prearranged into signalling islands.
This work clearly demonstrates the power of NSOM as an imaging technique. Its application to other signalling receptors could provide valuable insights into the signalling events that occur in both healthy and diseased cells.
John Paul Pezacki (Steacie Institute for Molecular Sciences and Chemical Biology, National Research Council Canada, Ottawa, Canada)
Additional contact for comment on paper:
Krzysztof Palczewski (University of Washington, Seattle, WA, USA)
Abstract available online.
(C) Nature Chemical Biology press release.
Message posted by: Trevor M. D'Souza