Mass Spectrometry Measurements of Neuropeptides: From Identification to Quantitation

Abstract

Neuropeptides (NPs), a unique class of neuronal signaling molecules, participate in a variety of physiological processes and diseases. Quantitative measurements of NPs provide valuable information regarding how these molecules are differentially regulated in a multitude of neurological, metabolic, and mental disorders. Mass spectrometry (MS) has evolved to become a powerful technique for measuring trace levels of NPs in complex biological tissues and individual cells using both targeted and exploratory approaches. There are inherent challenges to measuring NPs, including their wide endogenous concentration range, transport and postmortem degradation, complex sample matrices, and statistical processing of MS data required for accurate NP quantitation. This review highlights techniques developed to address these challenges and presents an overview of quantitative MS-based measurement approaches for NPs, including the incorporation of separation methods for high-throughput analysis, MS imaging for spatial measurements, and methods for NP quantitation in single neurons. Expected final online publication date for the Annual Review of Analytical Chemistry Volume 15 is June 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Assessment and Comparison of Database Search Engines for Peptidomic Applications

“…The decreasing frequency of peptide identification with shorter sequences (e.g., 5–9 residues) can partly be attributed to the fact that smaller peptides are more likely to be singly charged, reducing fragmentation as compared to multiply charged peptides, especially if basic residues such as arginine or lysine are present, resulting in low ion series production for confident peptide assignments . Furthermore, while some short peptides, such as enkephalins, are known to exert potent biological effects, various forms of peptide processing are often observed in peptidomics, where the extended forms of these peptides are observed along with peptide fragments of more abundant structural proteins, thereby potentially skewing the peptide length distribution toward longer peptides in the range of 10–20 residues. , …”

“…29 Furthermore, while some short peptides, such as enkephalins, are known to exert potent biological effects, various forms of peptide processing are often observed in peptidomics, where the extended forms of these peptides are observed along with peptide fragments of more abundant structural proteins, thereby potentially skewing the peptide length distribution toward longer peptides in the range of 10−20 residues. 30,31…”

Human iN neuronal model of schizophrenia displays dysregulation of chromogranin B and related neuropeptide transmitter signatures

“…Peptide neurotransmitters, known as neuropeptides, comprise the largest portion of transmitters in the nervous system [ 11 – 15 ]. Active neuropeptides are derived from proneuropeptide precursors by proteolytic processing [ 11 , 12 ].…”

Data-Driven Deciphering of Latent Lesions in Heterogeneous Tissue Using Function-Directed t-SNE of Mass Spectrometry Imaging Data

“…Mass spectrometry imaging (MSI) has been a prominent analytical technique for linking molecular histology with functional activities, thus enabling both high-throughput mapping of molecules and biochemical characterization of tissue morphology. − MSI has been reported for mapping metabolites, , lipids, − neuropeptides, , glycans, and local protein extracts in highly heterogeneous tissue for their functional analysis. The potential advantage of MSI-based molecular histology is the ability to complement established histological and histochemical approaches by uncovering molecular differences that were previously unknown.…”