Study of the TSPO Translocator Protein: A Key Marker in Neuroimaging

Full description

Membrane proteins play a central role in many cellular functions and represent 60% of therapeutic targets. Yet, they comprise only 3% of the structures in the Protein Data Bank (PDB). Their study remains a major challenge due to the difficulties associated with producing them in a native state.

We are studying the TSPO translocator protein, a small mitochondrial membrane protein present in the nervous system. Although its exact role is still debated, TSPO is a key target in neuroimaging, particularly used in positron emission tomography (PET scans) as a marker of brain inflammation in trauma, cancers, and neurodegenerative diseases (Alzheimer’s, Parkinson’s).

Currently, the only high-resolution structure of mammalian TSPOs (mTSPO, from mouse) available (NMR, PDB:2MGY) is controversial: produced in the bacterium E. coli, the protein is unfolded and stabilized by a ligand, which stiffens its structure.

Our goal is to study the structure/function relationship of mTSPO, both with and without ligand (apo form), by producing it under conditions close to its native state in S. cerevisiae yeast. Obtaining this structure is crucial for understanding the binding mechanisms and stability of ligands, which will allow the development of new molecules for imaging and therapy.

The internship aims to produce native apo-mTSPO. This protocol, already qualitatively tested (see Fig. 1) on the ProtEx expression platform (I2BC, Saclay), will be optimized to purify mTSPO in different environments, particularly using the detergent DDM, known to promote crystallization. The addition of a fluorescent fusion protein (GFP) will facilitate tracking these steps.

The second objective will be to characterize the structure of mTSPO produced using biophysical and strucural techniques: optical spectroscopy (absorbance, fluorescence, circular dichroism), light scattering (MALS), and small-angle X-ray and neutron scattering (SAXS at the SOLEIL synchrotron in St-Aubin, and SANS at the ILL neutron source in Grenoble). The results will be compared to its function by measuring its affinity for ligands using microscale thermophoresis (MST).

Profile sought: Student in biophysics, biochemistry, or physical chemistry, with a strong interest in structural biology. A possibility of pursuing a PhD is available.

The internship will take place at the Laboratoire Léon-Brillouin (LLB, CEA, CNRS, Univ. Paris-Saclay), in collaboration with Dr. José Luis Vázquez-Ibar (I2BC, Univ. Paris-Saclay).

Contact: Dr. Sophie COMBET (CNRS Research Director); 01 69 08 67 20;

References:

1. Saade C, Pozza A, Bonnete F, Finet S, Lutz-Bueno V, Tully MD, Varela PF, Lacapere JJ, Combet S. Enhanced structure/function of mTSPO translocator in lipid :surfactant mixed micelles. Biochimie 224, 3, 2024.

2. Combet S, Bonneté F, Finet S, Pozza A, Saade C, Martel A, Koutsioubas A, Lacapère JJ. Effect of amphiphilic environment on the solution structure of mouse TSPO translocator protein. Biochimie 205, 61-72, 2023.
Laboratoire Léon Brillouin (LLB) – CEA SACLAY – 91191 GIF-SUR-YVETTE CEDEX (FRANCE) Tél. : 01 69 08 67 20 – e-mail :

Location

CEA Saclay, (91) Essonne, France

Internship conditions

• Internship duration: 6 months
• Level of study: Bac+5
• Training: Master 2
• Continuation in PhD thesis: Yes
• Application deadline: 3 février 2025

Useful methods and technics:
Production of a membrane protein (using a known protocol). Structural characterization through optical spectroscopy (circular dichroism, fluorescence), light scattering (MALS), and small-angle X-ray and neutron scattering (SAXS/SANS) on large-scale facilities (SOLEIL, ILL). Functional characterization using microscale thermophoresis (MST). Data analysis involving modeling and interactive simulations.

Supervisor

Sophie COMBET
Phone: +33 1 69 08 67 20
Email :