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. 2019 Nov 20;8:e48718. doi: 10.7554/eLife.48718

Figure 3. DCC and Nrp1 are in close proximity to ribosomes in axonal growth cones in a cue-dependent manner.

(A) Expansion imaging shows partial co-localization of DCC and (B) Nrp1 with ribosomal proteins (Scale bars, 5 μm). (C) Representative proximity ligation assay signal in axonal growth cones between DCC and RPL5/uL18, RPS4X/eS4 or IgG control (Scale bars, 5 μm). (D) Representative proximity ligation assay signal in axonal growth cones between Nrp1 and RPS3A/eS1, RPS23/uS12 or IgG control (Scale bars, 5 μm). (E) Representative PLA signal in axonal growth cones between EphB2 and RPL5/uL18 (left) and quantification of PLA signal in axonal growth cones compared to DCC-RPL5/uL18 or Nrp1-RPS23/uS12 (right) (Mann-Whitney test; three biological replicates; bars indicate mean, error bars indicate SEM, ***p<0.0001; Scale bars, 5 μm). (F) EM image of an unstimulated axonal growth cone showing ribosomes aligned in a row (red arrows) under plasma membrane (PM). Inset shows the growth cone at lower magnification; the red box indicates the area shown in higher magnification. The section glances through the extreme surface of growth cone, where it attaches to the culture dish, giving rise to areas that lack subcellular structure. (G) Distribution frequency of the inter-ribosome distance in nm of ribosomes in axonal growth cones (n = 20) or in RGC soma (n = 5). All distances larger than 100 nm were pooled together. (H, I, J, K) Quantification of PLA signal in cue-stimulated axonal growth cones relative to control (unpaired two-tailed t-test; bars indicate mean, error bars indicate SEM; ***p<0.0001; *p=0.0423; for n.s. in J p=0.3522; for n.s. in K, p=0.885). (L) Relative PLA quantification of DCC and RPL5/uL18 compared to control after Dynasore pre-treatment (50 μM for 20 min), Netrin-1, or Netrin-1 + Dynasore (one-way ANOVA with Bonferroni’s multiple comparisons test; bars indicate mean, error bars indicate SEM; p=0.001027 for Control vs. Netrin-1, p=0.000402 for Netrin-1 vs Netrin-1 + Dynasore, p=0.590377 for Control vs. Dynasore, p=0.384848 for Control vs Netrin + Dynasore). For all PLA experiments, numbers in bars indicate total number of growth cones quantified from at least three independent experiments.

Figure 3—source data 1. Spreadsheet containing PLA counts and relative comparisons from each axonal growth cone in Figure 3E, all inter-ribosome distances and distribution shown in Figure 3G, and all normalized PLA count values for each axonal growth cone in Figure 3H–L.

Figure 3.

Figure 3—figure supplement 1. DCC and Nrp1 are in close proximity to ribosomes in axonal growth cones in a cue-dependent manner.

Figure 3—figure supplement 1.

(A) Pearson’s Correlation coefficients of DCC-RPL5/uL18 and Nrp1-RPS3A/eS1 from expanded axonal growth cones (data obtained from four biological replicates, bars indicate mean, error bars indicate SEM). (B) PLA images showing DCC and RPL10A/uL1 are in close proximity in axonal growth cones, whereas DCC and IgG control generates little to no PLA signal. Scale bars, 5 μm. (C–E) EM images of an unstimulated axonal growth cone (C), a growth cone lamellipodium (D) and a retinal ganglion cell body (E). Ribosomes can be seen aligned in rows (red arrows) or isolated (white arrow) under the plasma membrane and as polysomes (blue arrows) in the cell body. (F) PLA signal between DCC and hnRNPA2B1 does not decrease after a 2 min Netrin-1 stimulation in axonal growth cones (Mann-Whitney test; bars indicate mean, error bars indicate SEM; p=0.2886; representative PLA images are shown). (G) Sema3A stimulation at protein-synthesis independent concentration does not decrease puromycin levels in axonal growth cones (Mann-Whitney test; bars indicate mean, error bars indicate SEM; p=0.2487; representative images are shown) or (H) PLA signal between Nrp1 and RPS3A/eS1 (Mann-Whitney test; bars indicate mean, error bars indicate SEM; p=0.2555). For all Expansion microscopy, PLA and QIF experiments, numbers in bars indicate amount of growth cones quantified collected from at least three independent experiments.
Figure 3—figure supplement 1—source data 1. Spreadsheet containing all Pearson’s correlation values for each expanded growth cone in Figure 3—figure supplement 1A, all normalized PLA count values for each axonal growth cone in Figure 3—figure supplement 1F and H, and all normalized puromycin intensity values for each axonal growth cone in Figure 3—figure supplement 1G.