Journal: bioRxiv
Article Title: Cryo-electron tomography pipeline for plasma membranes
doi: 10.1101/2024.06.27.600657
Figure Lengend Snippet: a, TIRF microscopy of a HEK293 cell expressing FerriTag (FRB-mCherry-FTH1, magenta, and FTL) and Hip1R-GFP-FKBP (green) shown before rapamycin addition (left) and 30-60 seconds after rapamycin addition (right). b, Cryo-fluorescence microscopy of HEK293 isolated plasma membrane on a grid expressing FerriTag (FRB-mCherry-FTH1, magenta, and FTL) and Hip1R-GFP-FKBP (green) with combined colors on the right. c (left), CryoEM montaged map of the same grid square. c(middle), Reflection image acquired on the cryo fluorescence microscope and used to register the images. c(right), Registered fluorescence and EM images combined. Orange dots = membrane outline, arrows = position of d acquisition. d, Tomogram of Hip1R/FerriTag labelling and an example of a prominent clathrin structure (right). Empty FerriTag structures are clearly visible as 12 nm circles (arrow). e, Selected tomogram from HEK293 cells with labeled FerriTag on GFP-FKBP-LCa shown and an example of a well-defined clathrin structure (right). For d and e , a cartoon at the top right depicts the location of the membrane (gray), clathrin (green), and FerriTag (purple). f, A histo-gram of the FerriTag distance from clathrin coated membrane (shown at 0-600 nm and 0-80 nm) for clathrin light chain (GFP-FKBP-LCa) and Hip1R (Hip1R-GFP-FKBP). Molecular models of Ferritin (PDB-1fha), mCherry (PDB-2h5q), FRB/FKBP (PDB-3fap), and GFP (PDB-5wwk) and EM density of the clathrin cage (emdb-21608) at scale with the zoomed-in histogram in combination with cartoons of Hip1R, actin, and membrane are shown as putative models explaining the data to the left. The dashed orange line guides the eye from the data peaks to the center of the FerriTag model. g, An example of FerriTag Hip1R labeling and surrounding a clathrin structure. Segmentation of membrane (gray), clathrin (green), FerriTag (purple) and actin (blue) are shown to the right. h, Close-up examples showing Hip1R density adjacent to FerriTag. Cartoons of membrane (light gray), clathrin (green), Hip1R (dark gray), FerriTag (purple), and actin (blue) are shown to the right to aid image interpretation. Tomogram images in d,e are minimum intensity projections (mIPs) of 21 Gaussian-smoothed XY slices. Tomogram images in g,h are mIPs of 10 Gaussian-smoothed slices. Scale bars are a, 20 μm, 8 μm inset full-width; b,c, 10 μm; d,e, 200 nm, 50 nm inset; g, 100 nm; h, 30 nm.
Article Snippet: To generate inducible cells expressing Dynamin1(K44A)-GFP, parental Flp-In T-Rex HEK293 cells (Thermo Fisher, R78007) were co-transfected with a 1:5 mass ratio of pcDNA/TO/Dyn1-K44A-GFP and the Flp recombinase expression plasmid, pOG44 (Thermo Fisher, V600520 ) using Lipofectamine 3000 (Invitrogen, L3000-015) following manufacturer’s instructions.
Techniques: Microscopy, Expressing, Fluorescence, Isolation, Membrane, Labeling