On the difficulties of characterizing weak protein interactions that are critical for neurotransmitter release. Issue 11 (2nd September 2022)

• Record Type: Journal Article
• Authors: Rizo, Josep; David, Guillaume; Fealey, Michael E.; Jaczynska, Klaudia
• Other Names: Rizo Josep guestEditor.
• Is Part Of: FEBS open bio. Volume 12:Issue 11(2022)
• Page Start: 1912
• Page End: 1938
• Publication Date: 2022-09-02
• Subjects: complexin -- membrane fusion -- neurotransmitter release -- SNAREs -- synaptotagmin -- weak protein interactions; Molecular biology -- Periodicals; Cytology -- Periodicals; Life sciences -- Periodicals; Biological Science Disciplines -- Periodicals; Molecular Biology -- Periodicals; Cell Biology -- Periodicals; Cytology; Life sciences; Molecular biology; Periodicals; 572.805
• DOI: 10.1002/2211-5463.13473
• Languages: English
• ISSNs: 2211-5463

Abstract

Abstract : The mechanism of neurotransmitter release has been extensively characterized, showing that vesicle fusion is mediated by the SNARE complex formed by syntaxin‐1, SNAP‐25 and synaptobrevin. This complex is disassembled by N ‐ethylmaleimide sensitive factor (NSF) and SNAPs to recycle the SNAREs, whereas Munc18‐1 and Munc13s organize SNARE complex assembly in an NSF‐SNAP‐resistant manner. Synaptotagmin‐1 acts as the Ca 2+ sensor that triggers exocytosis in a tight interplay with the SNAREs and complexins. Here, we review technical aspects associated with investigation of protein interactions underlying these steps, which is hindered because the release machinery is assembled between two membranes and is highly dynamic. Moreover, weak interactions, which are difficult to characterize, play key roles in neurotransmitter release, for instance by lowering energy barriers that need to be overcome in this highly regulated process. We illustrate the crucial role that structural biology has played in uncovering mechanisms underlying neurotransmitter release, but also discuss the importance of considering the limitations of the techniques used, including lessons learned from research in our lab and others. In particular, we emphasize: (a) the promiscuity of some protein sequences, including membrane‐binding regions that can mediate irrelevant interactions with proteins in the absence of their native targets; (b) the need to ensure that weak interactions observed in crystal structures are biologically relevant; and (c) the limitations of isothermal titration calorimetry to analyze weak interactions. Finally, we stress that even studies that required re‐interpretation often helped to move the field forward by improving our understanding of the system and providing testable hypotheses. Abstract : The variety of synaptotagmin‐1‐SNARE interactions that have been described illustrates the challenges involved in determining the protein interactions that control the different steps leading to Ca 2+ ‐triggered synaptic vesicle fusion.