We developed a method for labeling individual recombinant biotinylated neurexin and neuroligin molecules using monomeric streptavidin (mSA) conjugated to photostable Atto dyes. These small monomeric ligands (3 nm) do not induce cross-linking as divalent antibodies or streptavidin tetramers do, and provide excellent penetration into synaptic junctions (20 nm).
mSA can be combined with GFP nanobodies in an orthogonal labeling strategy that allows unprecedented dual-color visualization of NRX/NLG trans-synaptic contacts. We report a differential dynamics and nanoscale organization of the two NRX1 post-synaptic counter-receptors NLG1 and LRRTM2, compatible with divergent physiological roles (Chamma et al., Nat Comm, 2016).
This versatile technique is applicable to virtually any membrane molecule and compatible with a wide range of super-resolution microscopy techniques, including uPAINT (Universal Point Accumulation In Nanoscopic Topography), STORM (Stochastic Optical Reconstruction Microscopy), and STED (STimulated Emission Depletion).