Mass Spectrometry Approaches Empowering ...

Access through your organization

Check access to the full text by signing in through your organization.

Access through your organization

Section snippets

I. Introduction: A Century of Neuropeptide/Hormone Discovery: Where Are We and Where Are We Going?

Recognition of endogenous peptides as a novel class of bioactive molecules has led to ground-breaking discoveries in physiology, endocrinology, neuroscience, and ultimately, medicine in a historically short period of time – about a century. Acting as neurotransmitters, neuromodulators, and hormones, endogenous peptides regulate complex systemic functions and numerous behaviors in animals ranging from hydra to humans.

One of the first potent peptides discovered, β-alanyl-l-histidine, was

A. Neuropeptide Biosynthesis and Processing

Neuropeptides are synthesized, stored, and released by neurons of the central and peripheral nervous system, as well as by neuroendocrine cells throughout the body (see Fig. 1). The key features that distinguish these native peptides from other classes of regulatory molecules are their biosynthesis, mechanism of secretion, and bioactivity at low concentrations. Neuropeptides are enzymatically cleaved from larger precursor proteins (called prohormones) that are translated from the protein-coding

III. Methods of Neuropeptide Discovery and Characterization

Historically, sequencing via Edman degradation (Edman, 1950) was the earliest effective method for elucidating the primary sequence of peptides. Developed in 1950, the method identifies a protein/peptide sequence by sequentially removing the N-terminal amino acid. Although it is robust and easy to perform, Edman sequencing is slow, requires a high degree of peptide purification, and is best-suited to peptides without N-terminal PTMs. The limitations of Edman sequencing are easily overcome by

IV. From Discovery to Function

Historically, neuropeptides and peptide hormones were discovered using biologic activity-based screening of extracts of brain or endocrine tissue, followed by rounds of purification where the active fractions were tracked until a pure substance could be isolated. Insulin, substance P, oxytocin, and many others were purified from complex extracts via heroic efforts in processing mountains of organs until a sole fraction retaining the activity was isolated (Du Vigneaud et al., 1953; Burgus et

V. Unusual Routes to Peptide Formation and Function

Generally, to be classified as a cell-cell signaling molecule, a peptide must satisfy several criteria: i) be synthesized via the secretory pathway and released upon stimulation; ii) show specificity toward receptors on target cells and elicit downstream chemical changes upon binding; and iii) be regulated in the temporal and/or spatial domain (Malandrino and Smith, 2018). However, there have been increased reports of peptides that perform a signaling role but do not follow the above-stated

A. Chemical Basis of Peptide Therapeutics

Peptide and protein therapeutics have experienced significant advances in their clinical utility over the last several decades, with over 200 Food and Drug Administration (FDA) approvals in the United States (Fosgerau and Hoffmann, 2015; Usmani et al., 2017). Monoclonal antibodies and soluble portions of receptors make up an increasing share of the therapeutic drug market (Elgundi et al., 2017; Urquhart, 2019). In addition to antibodies and receptor fragments, hormone-like peptides are

VII. Conclusions

Despite its relatively short history, MS-based neuropeptide discovery and characterization has been applied to the exploration of neuropeptide mechanisms of human disease processes and provided novel neuropeptide targets for drug development. Monitoring neuropeptides as biomarkers of pathology or drug responses has become instrumental in the expansion of translational research. It is already well established that neuropeptide-based therapies offer significant advantages over existing

Authorship Contributions

Wrote or contributed to the writing of the manuscript: Anapindi, Checco, Romanova, Sweedler.

This work was supported by the National Institutes of Health National Institute on Drug Abuse [Grant P30-DA018310] to J.V.S. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

No author has an actual or perceived conflict of interest with the contents of this article.