NEUROtransmitter TRANSporters: from single molecules to human pathologies

Project Information

NeuroTrans

Grant agreement ID: 860954

DOI

10.3030/860954

Project closed

EC signature date 5 February 2020

Start date 1 February 2020

End date 31 July 2024

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 3 994 422,12

EU contribution

€ 3 994 422,12

Coordinated by

MEDIZINISCHE UNIVERSITAET WIEN
Austria

Periodic Reporting for period 2 - NeuroTrans (NEUROtransmitter TRANSporters: from single molecules to human pathologies)

Reporting period: 2022-02-01 to 2024-07-31

Summary of the context and overall objectives of the project

Neurons use electrical signals called action potentials to propagate information along axons and dendrites. In 1936 Otto Loewi received the Nobel Prize in Medicine for the discovery that small molecules (neurotransmitters) are used for inter-neuronal communication. Neuronal signalling requires efficient removal of the released neurotransmitters at synapses, typically achieved through re-uptake by dedicated transporters, the neurotransmitter transporters. Several diseases are associated with improper neurotransmitter clearance (Parkinson’s disease, seizures, anxiety, depression, or schizophrenia). Recreational drugs like cocaine or ecstasy interfere with transport processes and lead to hallucinations, euphoric stimulation, addiction.
The vision of the ETN NeuroTrans was to (i) gain an improved understanding on how neurotransmitter transporter dysfunction contributes to neuropsychiatric diseases and how psychoactive substances interfere with normal transporter function and (ii) to establish a robust framework for comprehending the molecular origin of diseases causing mutations.

The project’s ultimate objective was to develop a solid model that can predict changes in transporter function from fundamental principles and has defined the following scientific objectives:
(i) To obtain kinetic, structural, and mechanics insight into the processes of substrate transport.
(ii) To obtain improved electrophysiological, kinetic and thermodynamic data of substrate binding and transport.
(iii) To identify the molecular perturbations associated with neuropsychiatric disease.
(iv) To identify the mode of action of novel psychoactive substances.
(v) To develop or improve instruments and protocols for the quantification of neurotransmitter transporter function.

NeuroTrans has established a highly interdisciplinary doctoral training program by forming an interdisciplinary and intersectorial team of world-leading European researchers. Training included most important subdisciplines in quantitative biology, including molecular modelling, computer simulations, biophysics, biochemistry, neurobiology, molecular and structural biology and had a strong industry oriented focus, ensuring that the ESRs can become part of Europe’s future generation of innovative leaders.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

The NeuroTrans consortium used a very broad spectrum of methods and techniques to investigate neurotransmitter transporters, including the human transporters for dopamine (DAT), serotonin (SERT) and the gamma amino acid (GABA) transporters GAT1 and BGT-1, all essential for functioning of the human brain, as well as bacterial homologs thereof.
NeuroTrans has solved the structures of four neurotransmitter transporters in complex with ligands. Together with computational approaches these results revealed the structures of the transporters, their stoichiometry, and showed how substrates or inhibitors engage with the transporters. This is essential information to understand how transporters recognize substrates and how inhibitors block transporters.
Transporters need to flex, to change conformation and to cycle between an outward-facing and an inward-facing conformation to translocate substrate across biological membranes. Substrates of the studied neurotransmitter transporters bind to the outward-facing transporter and are later released on the intracellular side. We used several biophysical methods to investigate the dynamics of the transporters to investigate how they flex to achieve transport.
We have experimentally tested a large number of novel psychoactive substances (NPS). NPS are typically illegal and untested street drugs. Our work contributes to assess the level of hazard of these compounds, and to inform legislation.
Importantly, transport, as any other process, requires energy input. We combined computational free energy calculations with experiments that quantify binding affinities and driving forces. This knowledge is like a magic key that allows us to understand, and thus predict, how substances bind, and in which way the transporter changes conformation. We can use this knowledge to predict with increased certainty how other substances would interact with the same transporters, and are thus able to accelerate the assessment of the activity of e.g. NPS.
As for any other protein coded in the human genome, transporter mutants exist. We investigated many naturally occurring mutations of the dopamine transporter that are associated with psychological disorders. Our research showed how these mutations affect transporter function. Importantly, or results also point towards potential strategies, which could in the future lead to the development of medications that might specifically help patients after a careful selection through personalized medicine approaches.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

The NeuroTrans research programme will have major generalizable scientific impact that will be of high relevance to academia, pharmaceutical industry and policy makers. Its results are likely to be applicable not only to other classes of transporters, but to membrane proteins in general.
The strong translational aspects of NeuroTrans were established through the development of enabling techniques in biophysics and molecular biology together with industrial partners. Improved instruments to quantify transporter function and measure kinetics, dynamics and thermodynamic parameters, allowing for exploitation and commercialisation were launched by the industry beneficiaries Nanion and NanoTemper.
NeuroTrans characterized many novel psychoactive substances (NPS), which will create the basis for new legislation and thus is helping to ban these illegal and dangerous substances from the illegal street market in Europe. Importantly, and beyond expectation, we have identified substances that have a similar pharmacological profile as MDMA, but with improved safety properties because of higher metabolic stability. This is important and good news, because MDMA has been approved in Australia as an adjuvant for assisting psychotherapy of Post-Traumatic Stress Disorder (PTSD). MDMA has been shown to be very effective in improving the clinical situation of military soldiers after severe traumas from war situations, but it was not approved by the FDA for patient treatment on the basis of safety concerns. The MDMA analogs we discovered might show the way forward to find substances with improved safety that could become eligible for patient treatment.

Schematic image describing of the transport function of the dopamine transport