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. 2019 Jan 28;8:e43146. doi: 10.7554/eLife.43146

Figure 3. Multiple locations of FGF21-FGFR1c-βKlotho ternary complex in human adipocyte cells.

A composite image from several tomograms, with the cell surface membrane in blue, isosurface renderings of coated vesicle and endosomal membranes in cyan, isosurface renderings of a multivesicular body (MVB) and other vesicle membranes in violet and pink, clathrin in magenta, actin and microtubules in red and green (substituted with helical reconstructions from Figure 4), hexameric rings (substituted with subtomogram averages from Figure 4; putative p97 AAA+ ATPAse) in emerald, and AuNPs in yellow. Tomograms collected following treatment with AuNP-FGF21 for 1 h at 4°C show (1) a lamellopodium decorated with clusters of AuNP pairs, (2) filopodia surrounding clusters of AuNP pairs, (3) clusters of AuNP pairs on the cell surface, (4) AuNP pairs clustered in a coated pit, and (5) a clathrin-coated vesicle. Hexameric rings (putative p97 AAA+ ATPAse) are abundant in the vicinity of clathrin. A tomogram following treatment with AuNP-FGF21 for 1 h at 37°C shows an endosome associated with actin filaments (6) and a tomogram following treatment with AuNP-FGF21 overnight at 37°C shows a microtubule between an MVB and another vesicle (7). The arrows indicate a possible order of events, not an actual sequence; regions numbered 1–7 were taken from different tomograms.

Figure 3.

Figure 3—figure supplement 1. Activation and internalization cycle.

Figure 3—figure supplement 1.

Composite image of slices from several tomograms. Tomograms collected following treatment with AuNP-FGF21 for 1 h at 4°C, show (a) a lamellopodium decorated with clusters of AuNP pairs, (b) AuNP pairs clustered (right panel) on top of an invaginated membrane (middle panel) above a clathrin pit (left panel), and (c) a clathrin-coated vesicle; left panel showing AuNP pairs inside the vesicle, and right panel showing the clathrin cage. (d) Tomogram after 1 h treatment at 37°C, shows an endosome, tightly associated with actin filaments, with AuNP pairs inside, and (e) a vesicle presumably dividing, although merging cannot be ruled out. (f) Tomogram following overnight treatment at 37°C, shows a microtubule between a MVB, with unpaired AuNP inside (right panel) and other vesicle, with no AuNPs inside (putative late endosome). (For a complete mapping of AuNPs see Figure 4). AuNPs indicated by yellow arrows.