biostudies-literatureSturman DANHLBI NIH HHSNINDS NIH HHSL45-7https://www.ebi.ac.uk/biostudies/studies/S-EPMC1386803biostudies-literatureUnknown90(6)The acidity of mammalian secretory vesicles drives concentration and processing of their contents. Here, pH-sensitive green fluorescent protein (GFP) variants show that the > or =30-fold (H+) difference between secretory vesicles (pH < or = 5.7) and the cytoplasm (pH = 7.2) in mammalian cells is not present in peptidergic and small synaptic vesicles of the Drosophila neuromuscular junction. First, we find that fluorescence from Topaz-tagged atrial natriuretic factor, a peptidergic vesicle pH indicator, is only modestly affected by collapsing the H+ gradient in type III synaptic boutons. Quantitation shows that peptidergic vesicles are nearly neutral (pH = 6.74 +/- 0.05), even when temperature is elevated. Furthermore, small synaptic vesicles in glutamatergic synaptic boutons, studied with Biophysical journalNearly neutral secretory vesicles in Drosophila nerve terminals.PMC1386803NS32385R01 NS032385R01 HL080632Shakiryanova DHewes RSLevitan ESSturman DADeitcher DLfalseNearly neutral secretory vesicles in Drosophila nerve terminals.The acidity of mammalian secretory vesicles drives concentration and processing of their contents. Here, pH-sensitive green fluorescent protein (GFP) variants show that the > or =30-fold (H+) difference between secretory vesicles (pH < or = 5.7) and the cytoplasm (pH = 7.2) in mammalian cells is not present in peptidergic and small synaptic vesicles of the Drosophila neuromuscular junction. First, we find that fluorescence from Topaz-tagged atrial natriuretic factor, a peptidergic vesicle pH indicator, is only modestly affected by collapsing the H+ gradient in type III synaptic boutons. Quantitation shows that peptidergic vesicles are nearly neutral (pH = 6.74 +/- 0.05), even when temperature is elevated. Furthermore, small synaptic vesicles in glutamatergic synaptic boutons, studied with 2006-01-01T00:00:00Z2006 Mar2025-04-04T13:41:42.779Z2019-03-27T01:26:03ZS-EPMC13868031642828210.1529/biophysj.106.080978