# Prototoxin Effects on Nicotinic Receptor Function

> **NIH NIH R01** · ST. JOSEPH'S HOSPITAL AND MEDICAL CENTER · 2020 · $551,972

## Abstract

SUMMARY / ABSTRACT
Tobacco use, and most-prominently cigarette smoking, is the leading cause of preventable death in the USA
and across the world. Smoking behavior is driven by addiction to nicotine, which exerts its effects through
nicotinic acetylcholine receptors (nAChR). Better understanding how nAChR function and expression is
regulated is thus crucial. Prototoxins are an extensive family of proteins which serve as physiologically
important regulators of multiple nAChR subtypes. However, the basis of prototoxins' nAChR subtype
selectivities, their interaction sites, the mechanisms by which they alter nAChR function, and their roles within
nicotine dependence pathways are largely undetermined. This application addresses these critical gaps in our
knowledge. Our Preliminary Data indicate that the prototoxin lynx1 allosterically regulates multiple isoforms of
α3β4*-, α4β2*- and α5*-nAChR, which have repeatedly been linked to human smoking behavior. We have also
observed differential macroscopic and single-channel functional effects of lynx1 across nAChR isoforms, which
provide ideal readouts for use in defining the sites at which lynx1/α3β4*-nAChR interactions occur. These
findings led us to our underlying hypothesis: that allosteric prototoxin effects arise from (generally well-
conserved) interactions with non-agonist-binding nAChR α(-)- subunit interfaces, and that differential outcomes
arise from the details of interactions at each prototoxin/nAChR interface. New Preliminary data also indicate
that rostral-IPN (IPR) GABA neurons, with a well-defined role in somatic nicotine withdrawal, coexpress α3β4*-
and α4β2*-nAChR, together with high levels of both α5 subunit and lynx1 mRNA. They therefore represent an
excellent, dependence-related, native system for studying with which nAChR population(s) α5 subunits
associate, and how lynx1 modulates these same nAChR populations in the IPN. We therefore are ideally
placed to compare functional outcomes of lynx1 modulation across the same defined nAChR populations in
native neurons and in vitro models, enhancing validation and interpretation of findings across these systems.
We will pursue this opportunity by combining precise experimental data from a multidisciplinary experimental
approach with sophisticated molecular dynamics modeling. This closely integrated research plan will allow us to
establish for the first time a generalized framework to understand how prototoxin modulators produce
functional outcomes across multiple nAChR subtypes and isoforms, in both native neurons and in vitro
expression systems. It will also ensure maintenance of scientific rigor, rapidly refine our experimental designs,
and produce key biological and mechanistic insights. In addition, regionally-restricted prototoxin expression may
permit modulation of nAChR function to be restricted to particular brain regions or cell types. Prototoxin/nAChR
interactions may therefore represent promising new drug targets. By probing the...

## Key facts

- **NIH application ID:** 9878094
- **Project number:** 5R01DA043567-03
- **Recipient organization:** ST. JOSEPH'S HOSPITAL AND MEDICAL CENTER
- **Principal Investigator:** Julie M. Miwa
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $551,972
- **Award type:** 5
- **Project period:** 2018-04-01 → 2023-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9878094

## Citation

> US National Institutes of Health, RePORTER application 9878094, Prototoxin Effects on Nicotinic Receptor Function (5R01DA043567-03). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9878094. Licensed CC0.

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