Advances in Mass Spectrometric Tools for Probing Neuropeptides

Abstract

Neuropeptides are important mediators in the functionality of the brain and other neurological organs. Because neuropeptides exist in a wide range of concentrations, appropriate characterization methods are needed to provide dynamic, chemical, and spatial information. Mass spectrometry and compatible tools have been a popular choice in analyzing neuropeptides. There have been several advances and challenges, both of which are the focus of this review. Discussions range from sample collection to bioinformatic tools, although avenues such as quantitation and imaging are included. Further development of the presented methods for neuropeptidomic mass spectrometric analysis is inevitable, which will lead to a further understanding of the complex interplay of neuropeptides and other signaling molecules in the nervous system.

Label-free Quantification of Proteins in Single Embryonic Cells with Neural Fate in the Cleavage-Stage Frog (Xenopus laevis) Embryo using Capillary Electrophoresis Electrospray Ionization High-Resolution Mass Spectrometry (CE-ESI-HRMS)

“…To this end, we demonstrated the detection/ quantification of a considerable number of proteins from ϳ20 ng protein digests from single blastomeres, approaching the total protein content of larger mammalian cells. Microscale sample preparation can help collect peptides and proteins with high sensitivity, using, for example, patch-clamp electrophysiological tools (62) and microanalysis probes (17,63). For smaller mammalian cells containing fewer amounts of proteins, addition of carrier proteins may be beneficial to minimize adsorptive losses for low-abundance proteins.…”

Single-cell mass spectrometry with multi-solvent extraction identifies metabolic differences between left and right blastomeres in the 8-cell frog (Xenopus) embryo

“…Other single-cell MS strategies incorporate a separation step to reduce chemical complexity and matrix effects prior to ionization and detection of small molecules. For example, peptides were characterized in neurons using microsampling with liquid chromatography 38 , metabolites from stimulated single heart cells were electrophoretically separated in lab-on-a-chip devices, 39 and capillary electrophoresis (CE) with ESI-HRMS was used to detect metabolites in isolated molluskan and mammalian single neurons 40–42 . We recently adapted CE-ESI-HRMS to single Xenopus blastomeres and quantified dorsal–ventral and animal–vegetal metabolic cell heterogeneity in the 16-cell embryo.…”

Single‐Cell Mass Spectrometry for Discovery Proteomics: Quantifying Translational Cell Heterogeneity in the 16‐Cell Frog (Xenopus) Embryo

“…[6] Continuous developments in HRMS sensitivity enabled untargeted (discovery) proteomics on progressively smaller populations of cells [1c, 7] with representative successes including the identification of 2000 proteins from 2000-4000 cells from single Langerhans islands, [8] 167 proteins from 500 breast cancer cells, [1a] 109 proteins from 100 HeLa cells, [9] and most recently, % 12 000 proteins in % 50 fertilized [10] and as ingle unfertilized egg of the South African clawed frog (Xenopus laevis). [11] Using advanced microsampling and discovery HRMS, [1c, 12] neuropeptides were characterized in single molluscan [13] and arthropod neurons [12] as well as cells in the mammalian pituitary gland and Langerhans islets.…”