Unbiased Thiol-Labeling and Top-Down Proteomic Analyses Implicate Multiple Proteins in the Late Steps of Regulated Secretion

Regulated exocytosis enables temporal and spatial control over the secretion of biologically active compounds; however, the mechanism by which Ca modulates different stages of exocytosis is still poorly understood. For an unbiased, top-down proteomic approach, select thiol- reactive reagents were us...

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Bibliographic Details
Published in:Proteomes 2019-09, Vol.7 (4), p.34
Main Authors: Furber, Kendra L, Backlund, Peter S, Yergey, Alfred L, Coorssen, Jens R
Format: Article
Language:English
Subjects:
2-dimensional gel electrophoresis
Bioactive compounds
Biological activity
Calcium
Cholesterol
Efficiency
Exocytosis
Gel electrophoresis
Lipids
Mass spectroscopy
Membrane fusion
Membranes
Peptides
Proteins
rab gtpase
Reagents
Secretion
secretory vesicle
Secretory vesicles
thiol-reactivity
Vesicle fusion
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Summary:Regulated exocytosis enables temporal and spatial control over the secretion of biologically active compounds; however, the mechanism by which Ca modulates different stages of exocytosis is still poorly understood. For an unbiased, top-down proteomic approach, select thiol- reactive reagents were used to investigate this process in release-ready native secretory vesicles. We previously characterized a biphasic effect of these reagents on Ca -triggered exocytosis: low doses potentiated Ca sensitivity, whereas high doses inhibited Ca sensitivity and extent of vesicle fusion. Capitalizing on this novel potentiating effect, we have now identified fluorescent thiol- reactive reagents producing the same effects: Lucifer yellow iodoacetamide, monobromobimane, and dibromobimane. Top-down proteomic analyses of fluorescently labeled proteins from total and cholesterol-enriched vesicle membrane fractions using two-dimensional gel electrophoresis coupled with mass spectrometry identified several candidate targets, some of which have been previously linked to the late steps of regulated exocytosis and some of which are novel. Initial validation studies indicate that Rab proteins are involved in the modulation of Ca sensitivity, and thus the efficiency of membrane fusion, which may, in part, be linked to their previously identified upstream roles in vesicle docking.
ISSN:2227-7382
2227-7382
DOI:10.3390/proteomes7040034