NPS

Neuropeptide S (NPS) is a 20-amino-acid neuropeptide that functions as the endogenous ligand for the G protein-coupled receptor NPSR1, coupling to both calcium mobilization (via IP3 and ryanodine receptor-mediated ER release followed by store-operated calcium entry) and cAMP signaling pathways to regulate arousal, anxiety, and memory (PMID:25714705, PMID:28267583). Biased agonism studies demonstrate that NPS-driven locomotor stimulation depends on the cAMP pathway, whereas anxiolytic and memory-consolidating effects are mediated through the calcium mobilization pathway (PMID:28267583). In the hippocampal CA1 region, NPS is internalized into NPSR-expressing neurons via receptor-ligand complex endocytosis and modulates glutamatergic synaptic plasticity (PMID:22278093). NPS-producing neurons in the brainstem are Atoh1-derived, Foxp2-expressing cells concentrated in the parabrachial nucleus, with additional populations in the nucleus incertus, anterior hypothalamus, and lateral habenula (PMID:36036349).

1. 2010 High

   Establishing that all major behavioral and neuroendocrine effects of NPS — hyperlocomotion, anxiolysis, and corticosterone release — require NPSR1, confirming it as the sole functional receptor for NPS in vivo.

   Evidence NPSR1 knockout mice with ICV NPS injection and behavioral/neuroendocrine phenotyping

   PMID:20171785

   Open questions at the time

   • Downstream intracellular signaling pathways mediating each behavioral effect were not dissected
   • Whether compensatory mechanisms exist in knockout animals was not addressed
2. 2012 High

   Demonstrating that NPS enters neurons through receptor-mediated internalization and modulates hippocampal glutamatergic synaptic plasticity, providing a cellular mechanism for NPS effects on memory and cognition.

   Evidence Fluorophore-conjugated NPS tracking in brain slices and cell culture; single-neuron imaging; intranasal delivery with behavioral and proteomic readouts in mice

   PMID:22278093

   Open questions at the time

   • The specific glutamatergic proteins regulated and the signaling cascade from receptor internalization to plasticity changes were not fully resolved
   • Whether internalization is required for synaptic modulation or is merely a desensitization event was not distinguished
3. 2012 Medium

   Extending NPS function beyond the CNS by showing it drives monocyte chemotaxis via NPSR, establishing a peripheral immunomodulatory role.

   Evidence In vitro chemotaxis assay with human monocytes; pharmacological blockade with multiple selective NPSR antagonists

   PMID:23142110

   Open questions at the time

   • In vivo immune relevance and physiological NPS concentrations at immune cell sites are unknown
   • Downstream signaling pathway in monocytes was not characterized
4. 2015 High

   Resolving the intracellular calcium signaling cascade downstream of NPSR1, showing sequential IP3 receptor and ryanodine receptor-mediated ER calcium release followed by store-operated calcium entry.

   Evidence Single-cell calcium imaging with pharmacological dissection in primary hippocampal neurons expressing human NPSR1

   PMID:25714705

   Open questions at the time

   • The G protein subtype coupling NPSR1 to IP3 generation was not identified
   • Whether the same calcium signaling cascade operates in non-hippocampal NPS target neurons was not tested
5. 2017 High

   Dissecting biased agonism at NPSR1 revealed that cAMP signaling drives locomotor stimulation while calcium mobilization mediates anxiolysis and memory consolidation, separating therapeutic from side-effect pathways.

   Evidence Structure-activity relationship of truncated NPS analogs in calcium and cAMP assays; behavioral validation in rodents

   PMID:28267583

   Open questions at the time

   • The molecular determinants on NPSR1 that confer pathway-selective coupling were not identified
   • Whether biased agonism translates to human physiology is untested
6. 2022 Medium

   Mapping the developmental origin and molecular identity of NPS-producing neurons revealed they are Atoh1-derived, Foxp2-expressing parabrachial cells, distinct from other known PB populations, and identified novel NPS populations in the nucleus incertus, anterior hypothalamus, and lateral habenula.

   Evidence In situ hybridization, immunofluorescence, and Cre-reporter labeling in mice

   PMID:36036349

   Open questions at the time

   • Functional contributions of each anatomically distinct NPS neuron population to behavior remain undefined
   • Circuit-level connectivity of NPS neurons to NPSR1-expressing target areas was not mapped

• The structural basis of NPS–NPSR1 interaction, the G protein subtype coupling specificity, and the circuit-level logic by which discrete NPS neuron populations drive distinct behavioral outputs remain unresolved.
• No crystal or cryo-EM structure of the NPS–NPSR1 complex exists
• Selective ablation or activation of individual NPS neuron populations has not been performed
• Endogenous release dynamics of NPS under physiological conditions are not characterized