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Probing the stoichiometry of membrane proteins by single-molecule localization microscopy
December 2015. Many cell-surface proteins such as ion channels, transporters and receptors are suspected of forming oligomers or even changing their oligomeric state in order to fulfill a certain task. Several membrane receptors including G protein-coupled receptors, cytokine and growth factor receptors have been proposed to oligomerize upon ligand binding, presumably a prerequisite for intracellular signal initiation.
Advances in single-molecule fluorescence imaging have brought molecular counting within the native membrane environment in direct reach. However, rigorous single-molecule studies of membrane protein organization and stoichiometry on intact cells have been rare so far due to technical challenges and methodological limitations. A team of scientists lead by Mike Heilemann from the Institute of Physical and Theoretical Chemistry has addressed these challenges through the development of a counting strategy based on single-molecule localization microscopy to super-resolve protein structures in intact cells and basic quantitative evaluation. The method is capable of reporting the oligomeric state of dense, membrane-bound protein complexes. This approach should prove very valuable for scientists striving for reliable molecular counting in cells.
The team validated the new method with membrane-bound monomeric CD86 and dimeric cytotoxic T-lymphocyte-associated protein as model proteins and confirmed their oligomeric states. They also detected oligomerization of CD80 and vesicular stomatitis virus glycoprotein and proposed coexistence of monomers and dimers for CD80 and trimeric assembly of the viral protein at the cell membrane. Further information ...
Contact:
Mike Heilemann
Institute of Physical and Theoretical Chemistry
Goethe University Frankfurt
Max von Laue Straße 9
60438 Frankfurt, Germany
Heilemann@chemie.uni-frankfurt.de
Full reference:
Franziska Fricke, Joel Beaudouin, Roland Eils & Mike Heilemann (2015) One, two or three? Probing the stoichiometry of membrane proteins by single-molecule localization microscopy. Scientific Reports 5, article no. 14072, doi:10.1038/srep14072. Link