Mnb suppresses ADBE but promotes CME. (A) Schematic of stimulation protocols activating CME (top) and CIE (bottom). (B) Representative images of NMJ loaded with FM1-43 using the CME or CIE protocol as indicated (pseudo-colored). Arrowheads highlight the punctate membrane labeling indicative of bulk endocytosis. (C) Relative FM1-43 loading intensity normalized to control NMJ (CME: control, n = 26; mnb¹, n = 14; mnb OE, n = 10; mnb¹; mnb OE, n = 15; CIE: control, n = 12; mnb¹, n = 14; mnb OE, n = 11; mnb¹; mnb OE, n = 10). (D) Normalized internalized membrane area seen following FM1-43 loading using the CIE protocol (control, n = 12; mnb¹, n = 14; mnb OE, n = 11; mnb¹; mnb OE, n = 10). (E) Representative images of control NMJ loaded with fluorescent dextran during different stimulation conditions. Quantification of dextran index was determined by counting the number of boutons with dextran uptake (red) and normalizing to the total bouton number (highlighted by HRP, green). Fold change was normalized to unstimulated (unstim) control (−CPZ: unstimulated: n = 12; 1 Hz, n = 13; 10 Hz, n = 13; KCl, n = 13; 10 Hz 30 s, n = 6. +CPZ: unstimulated: n = 6; 1 Hz, n = 6; 10 Hz, n = 14; KCl, n = 5; 10 Hz 30 s, n = 6). (F) Mnb suppresses ADBE assayed by dextran uptake following 10 Hz stimulation for 10 min (control, n = 11; mnb¹, n = 12; mnb OE, n = 12; mnb¹; mnb OE, n = 9). (G) Acute inhibition of Mnb by proINDY enhances dextran uptake. NMJs were preincubated with DMSO (n = 14) or proINDY (n = 11) and stimulated at 10 Hz for 10 min. Scale bar = 2 µm in B and E–G). *, P < 0.05 compared with control or as indicated. n values indicate the number of NMJs assayed. All values represent mean ± SEM.