Fig. 7

Synaptic macropinocytosis-mediated downregulation of Tkv receptors. a Stimulation of neuromuscular junction (NMJ) macropinocytosis by recombinant Gbb. Sample confocal images of NMJ 6/7 boutons in the indicated genotypes labeled with anti-HRP (green) following pulse of TMR-Dex (70 kDa, 2 mg/ml, red) in both absence (− Gbb) and presence (+ Gbb) of Gbb (50 ng/ml, 5 min). b Quantification of TMR-Dex-positive macropinosomes (>0.2 μm diameter) per NMJ bouton. c Representative transmission electron microscopic images of control or Gbb-stimulated NMJ 6/7 boutons overexpressing bone morphogenetic protein receptor (BMPR) Tkv (C155-GAL4/+; UAS-Myc-tkv/+). d Macropinocytosis stimulation from postsynaptic Gbb driven by Mhc-GS-GAL4/UAS-gbb in early third instar (RU486 [3 mg/ml], 2 min), aged for 8 h to the late third instar. Sample images of NMJ 6/7 boutons from Mhc-GS-GAL4/+ (control) and Mhc-GS-GAL4/UAS-gbb labeled with anti-HRP (green) following pulse of TMR-Dex (2 mg/ml, 5 min, red). e Quantification of TMR-Dex-positive macropinosomes/NMJ bouton. f Single confocal sections of NMJ 6/7 boutons of the indicated genotypes stained with anti-HRP (green) and anti-Myc (red) under permeant conditions. g Quantification of BMPR intensities. Bar graphs indicate mean ± s.e.m. The number of NMJ branches analyzed for each genotype is indicated inside bars. Statistical analyses were performed by one-way analysis of variance with Tukey–Kramer post hoc test for b and g (Myc-Tkv) or by Student’s t test for e and g (Flag-Wit). Comparisons are made against Gbb-stimulated wild type (b), Mhc-GS-GAL4/+ (e), C155-GAL4/+; UAS-Myc-tkv/+ (g), or C155-GAL4/+; UAS-Flag-wit/+ (g, shaded) NMJs (*P < 0.001; **P < 0.01). Scale bars: a, d, f, 5 μm; c, 100 nm