Community Research and Development Information Service - CORDIS

Final Report Summary - SIGMA1R (Structural Basis of Sigma-1 Receptor Ligand Interactions)

The sigma-1 receptor is an endoplasmic reticulum (ER) integral membrane protein receptor is implicated in neurodegeneration, drug addiction, pain, amnesia, depression, Alzeimer’s disease, stroke, retinal neural degeneration, HIV infection, and cancer. In addition to its endogenous ligands, N,N- dimethyltryptamine (DMT) and the ER chaperone BIP, the sigma receptor binds a wide range of exogenous ligands and therapeutic compounds. Recent studies demonstrated potent antiapoptotic actions of Sigma-1, blocking neurodegeneration caused by beta-amyloid or ischemia. Other studies have shown sigma-1 antagonists capable of inhibiting tumor-cell proliferation. Despite numerous drug interactions, very little structural information about the sigma-1 receptor is available, partly because it does not share sequence homology with any other mammalian protein.

The main goals of the project is to solve the 3D structure of Sigma-1 by solution state NMR and characterise its ligand interactions at an atomic level and their regulation by cholesterol and ion binding. With a novel mammalian cell expression and isotopic labelling strategy and in- vivo assays we intended to further validate our work in-vivo with the aim of feeding our findings into the understanding of the Sigma-1 function in the cell and its modulation by drug binding.

We have been able to express and purify natively the full length Sigma-1 receptor (S1R) in detergent micelles with different isotopic labelling schemes. The integrity of the protein has been assessed looking at its secondary structure and activity. We have found that, in the conditions of the study, S1R is able to bind drugs with high affinity, interact with BiP (an ER HSP70 family chaperone), and has chaperone activity.

Biophysical characterization of the protein has showed that S1R coexist in a mixture of oligomeric states in solution, all capable of binding drugs. Binding to BiP has also been characterized using biophysical techniques, as well as the chaperone activity under different conditions.

A high resolution crystal structure of the antagonist bound form of S1R has become available during the course of this project. This has helped mapping the residues that we have identified by NMR to be affected by drug binding (both agonists and antagonists) with atomic detail. We have also got chemical shift and backbone dynamics information of the free and bound forms.

Additionally, we have performed in-vivo studies of fluorescently tagged S1R looking at the cellular distribution of the protein and its oligomeric state, as well as the interactions of S1R with BiP inside the ER.

The results obtained in this project have enabled us to define the changes in structure and dynamics between the free and bound forms and map them into the structure, gaining insight in the allosteric mechanisms of S1R. Furthermore, we have been able to link different interactions of S1R with its chaperone activity, related to the cell stress response.

The main outcome of the project consists on the identification of the changes occurring upon agonist and antagonist binding of S1R, and how they modulate the activity of the protein and its interactions with other binding partners. This information is crucial for the effective design of therapeutic drugs against the neurological diseases where S1R is involved, particularly since there are currently different small molecules targeting S1R in clinical trials for the treatment of neurodegeneration and neuropathic pain.

Related information

Reported by

United Kingdom
Follow us on: RSS Facebook Twitter YouTube Managed by the EU Publications Office Top