Journal: Cellular and Molecular Life Sciences: CMLS

Article Title: Serotonin functions as a bidirectional guidance molecule regulating growth cone motility

doi: 10.1007/s00018-020-03628-2

Figure Lengend Snippet: 5-HT1b and 5-HT2a receptors are expressed in growth cones and filopodia. a–j Sensory neuron growth cones immunostained for serotonin receptors, 5-HT1b (green in a, red in g), 5-HT2a (green, d and h) as well as filamentous actin to highlight the extent of the growth cone (Phalloidin, red; b and e). The receptors 5-HT1b and 5HT2a were observed as a widespread punctate distribution throughout the growth cone (g–h). Punctate expression was evident in filopodia (j) with isolated 5-HT1b (green, *), 5-HT2a (red, #) as well as colocalised (arrowheads) puncta on filopodial shafts. There was prominent colocalization of 5-HT2a and 5-HT1b receptors in peripheral areas (i, arrow). Scale bars are 5 μm (a–i) and 1 μm (j). k Turning responses to serotonin were sensitive to chlorpromazine. Attractive turning of growth cones to 5HT-Lo (n = 7, p = <0.0001) and repulsion to 5HT-Hi (n = 8, p = 0.003) were significantly different when cultures were treated with chlorpromazine. l Axon extension was not significantly different in any experimental treatments (ns, p > 0.05). (Mann–Whitney u-test)

Article Snippet: Immunocytochemistry DRG sensory neurons were fixed with paraformaldehyde (PFA) (4%, Sigma-Aldrich) in phosphate buffered saline (PBS) overnight at 4 °C, washed in PBS (3 × 10 min), for some experiments, cells were permeabilised for 1 h with blocking solution (PBS containing 0.4% Triton X-100; 5% goat serum, Sigma-Aldrich & Gibco) and immunostained with a rabbit antibody to serotonin receptors 5-HT1b (1:500; Abcam) or 5-HT2a (1:500; Alomone Labs) in blocking solution overnight at 4 °C.

Techniques: Expressing, Isolation, MANN-WHITNEY

Journal: Cellular and Molecular Life Sciences: CMLS

Article Title: Serotonin functions as a bidirectional guidance molecule regulating growth cone motility

doi: 10.1007/s00018-020-03628-2

Figure Lengend Snippet: 5HT-Lo elicits growth cone attraction through the 5-HT2a receptor. a Growth cone attraction was measured in the presence of 5HT-Lo gradients (p = <0.0001) and TCB-2 gradients (p = 0.0002). Growth cone attraction to 5HT-Lo was abolished by pharmacological application of the selective 5-HT2a receptor antagonist, ritanserin (n = 17, p = 0.0001) and the PLC inhibitor, U-73122 (n = 9, p = 0.0018). b Growth cone attraction to 5HT-Lo was not perturbed when growth cones treated with a specific 5-HT1b antagonist, GR55562 (n = 8, p = <0.0001), or the 5-HT3 antagonist ondansetron (n = 8, p = 0.0082). Depletion of ER calcium with thapsigargin (n = 19, p = 0.0003) abolished attractive turning to 5HT-Lo, while inhibition of VGCCs with nifedipine (n = 15, p = 0.0330) had no significant effect. Turning angles were compared to vehicle and 5HT-Lo and only significant differences shown in (a) and (b). Kruskal–Wallis, Dunn’s multiple comparison test. c, d Axon extension was not significantly different in any experimental treatments (ns, p > 0.05). Kruskal–Wallis, Dunn’s multiple comparison test

Article Snippet: Immunocytochemistry DRG sensory neurons were fixed with paraformaldehyde (PFA) (4%, Sigma-Aldrich) in phosphate buffered saline (PBS) overnight at 4 °C, washed in PBS (3 × 10 min), for some experiments, cells were permeabilised for 1 h with blocking solution (PBS containing 0.4% Triton X-100; 5% goat serum, Sigma-Aldrich & Gibco) and immunostained with a rabbit antibody to serotonin receptors 5-HT1b (1:500; Abcam) or 5-HT2a (1:500; Alomone Labs) in blocking solution overnight at 4 °C.

Techniques: Inhibition, Comparison

Journal: Cellular and Molecular Life Sciences: CMLS

Article Title: Serotonin functions as a bidirectional guidance molecule regulating growth cone motility

doi: 10.1007/s00018-020-03628-2

Figure Lengend Snippet: 5HT-Hi promotes growth cone repulsion through the 5-HT1b receptor. a Growth cone repulsion was measured in the presence of 5HT-Hi gradients (p = <0.0001) and CP-94253 gradients (p = 0.0018). Growth cone repulsion to 5HT-Hi was altered to levels indistinguishable from random growth (vehicle) with application of the selective antagonist to 5-HT1b, GR55562 (n = 16, p = <0.0001), by activating adenylate cyclase with forskolin (n = 8, p = 0.0003) and restoration of cAMP signals with Sp-cAMPs (n = 8, p = 0.0001). b Repulsion to 5HT-Hi was not perturbed when growth cones were treated with the 5-HT2a receptor antagonist ritanserin (n = 8, p = 0.002) or the 5-HT3 antagonist ondansetron (n = 10, p = 0.0003). Inhibition of ER calcium release with thapsigargin (n = 10, p = <0.0001) or calcium influx with nifedipine (n = 8, p = <0.0001) did not alter growth cone repulsion from 5HT-Hi. Turning angles were compared to vehicle and 5HT-Hi. c, d Axon extension was not perturbed by any pharmacological application (ns, p > 0.05). Turning angles were compared to vehicle and 5HT-Hi. (Kruskal–Wallis, Dunn’s multiple comparison test)

Article Snippet: Immunocytochemistry DRG sensory neurons were fixed with paraformaldehyde (PFA) (4%, Sigma-Aldrich) in phosphate buffered saline (PBS) overnight at 4 °C, washed in PBS (3 × 10 min), for some experiments, cells were permeabilised for 1 h with blocking solution (PBS containing 0.4% Triton X-100; 5% goat serum, Sigma-Aldrich & Gibco) and immunostained with a rabbit antibody to serotonin receptors 5-HT1b (1:500; Abcam) or 5-HT2a (1:500; Alomone Labs) in blocking solution overnight at 4 °C.

Techniques: Inhibition, Hi-C, Comparison

Journal: Cellular and Molecular Life Sciences: CMLS

Article Title: Serotonin functions as a bidirectional guidance molecule regulating growth cone motility

doi: 10.1007/s00018-020-03628-2

Figure Lengend Snippet: 5HT-Lo exposure causes asymmetric distribution of 5-HT receptors to the turning or motile side of growth cones. Schematic a showing growth cone divided into “near” and “far” regions with respect to micropipet position (located on the upper left side). b–d Growth cones immunostained after turning in response to 5HT-Lo and stained for 5-HT2a (green, b), 5-HT1b (red, c) and merged in (d). Dotted line separates the near and far regions of growth cone (near vs far). (e) Representative image of filopodia with 5-HT2a (green), 5-HT1b (red) receptor puncta. (f) There was no significant near/far bias in the number of filopodia following exposure to 5HT-Lo (n = 8, p = 0.9004), 5HT-Hi (n = 13, p = 0.5450) or BDNF (n = 10, p = 0.7907) compared to vehicle. (Data not normally distributed: Kruskal–Wallis, Dunn’s multiple comparison test). g There were significantly more (n = 36, p = 0.0033) 5-HT2a puncta in filopodia on the near side of growth cones exposed to 5HT-Lo compared to all other treatments. h There was no bias in 5-HT1b puncta in filopodia of growth cones. (Mann–Whitney U-test). (i-j) When entire growth cones were analysed, i 5HT-2a (n = 9, p = 0.0006) and j 5HT-1b (n = 9, p = 0.0028) receptor translocation was significantly biased in growth cones exposed to 5HT-Lo. All ratios were compared to vehicle (Data normally distributed: Shapiro–Wilk. One-way ANOVA, Tukey’s multiple comparison test). Scale bars are 5 μm (Fig. 7b–d) and 1 μm (Fig. 7e)

Article Snippet: Immunocytochemistry DRG sensory neurons were fixed with paraformaldehyde (PFA) (4%, Sigma-Aldrich) in phosphate buffered saline (PBS) overnight at 4 °C, washed in PBS (3 × 10 min), for some experiments, cells were permeabilised for 1 h with blocking solution (PBS containing 0.4% Triton X-100; 5% goat serum, Sigma-Aldrich & Gibco) and immunostained with a rabbit antibody to serotonin receptors 5-HT1b (1:500; Abcam) or 5-HT2a (1:500; Alomone Labs) in blocking solution overnight at 4 °C.

Techniques: Staining, Comparison, MANN-WHITNEY, Translocation Assay

Journal: Cellular and Molecular Life Sciences: CMLS

Article Title: Serotonin functions as a bidirectional guidance molecule regulating growth cone motility

doi: 10.1007/s00018-020-03628-2

Figure Lengend Snippet: 5HT-Lo exposure causes asymmetric distribution of membrane 5-HT2a receptors to the motile side of growth cones. a–h Representative growth cones exposed to vehicle and 5HT-Lo gradients (micropipette on upper left side) and stained for membrane localization of receptors 5-HT1b (green, a, e), 5-HT2a (green, c, g) and merged with actin, (red, b, d, f, h). Dotted line separates the near and far regions of the growth cone. i Increase magnification of representative image h to show the presence of 5-HT2a receptor membrane on most filopodia (*) of the growth cone (yellow *, insets). Scale bars are 5 μm. (j-k)There was no significant near/far bias in the amount of f-actin (/area) (j) and the number of filopodia (k) in growth cones exposed to vehicle and 5HT-Lo. Kruskal–Wallis, Dunn’s multiple comparison post hoc test. (l) There was no significant bias in the total percentage of filopodia containing 5HT2a and 5HT1b puncta (60%). One-way ANOVA followed by Tukey’s multiple comparison post hoc test. (m) There was no significant near/far bias in the amount of 5-HT2a and 5-HT1b puncta per filopodia. (n) Analysis of 5-HT receptor membrane localization showed translocation of 5-HT2a (n = 18, p = <0.0001) to the near side of growth cones exposed to 5HT-Lo while no significant translocation of 5-HT1b (n = 15, p = 0.346) was observed. (Mann–Whitney U-test)

Article Snippet: Immunocytochemistry DRG sensory neurons were fixed with paraformaldehyde (PFA) (4%, Sigma-Aldrich) in phosphate buffered saline (PBS) overnight at 4 °C, washed in PBS (3 × 10 min), for some experiments, cells were permeabilised for 1 h with blocking solution (PBS containing 0.4% Triton X-100; 5% goat serum, Sigma-Aldrich & Gibco) and immunostained with a rabbit antibody to serotonin receptors 5-HT1b (1:500; Abcam) or 5-HT2a (1:500; Alomone Labs) in blocking solution overnight at 4 °C.

Techniques: Membrane, Staining, Comparison, Translocation Assay, MANN-WHITNEY