Research

Neuronal G-Protein Coupled Receptors

Our main interest are neuronal G-protein Coupled Receptors or GPCRs.

These sensory proteins are important targets of therapeutic and abused drugs, and are usually studied by pharmacology or electrophysiology, but I think that we cannot fully understand their function without taking into account their cellular environment, accessible by the methods of cell biology. Following these premises, we have indeed discovered an unexpectedly close relationship between neuropharmacology and neuronal cell biology.

Specifically, we are now aware that axonal GPCR function is highly constrained by the specificities of mature axons (Figure 1). Thus, our actual projects are targeted to decipher this closely intertwined relationship between GPCR activation and functional axonal structure.

Figure 1

Fig 1 : Cultured rat hippocampal neuron expressing CB1 cannabinoid receptors tagged with Green Fluorescent Protein (GFP in green). Surface-localized CB1Rs are labeled in blue while the endocytic protein clathrine is labeled in red. Microphotography by Christophe Leterrier.

The brain receptor of cannabinoids

Our main model GPCR is the CB1 cannabinoid receptor, one of the most abundant brain GPCRs and the brain target of Δ9-THC, the psychoactive component of marijuana. After having discovered a new axonal targeting model for CB1Rs (Figure 2) and having reported the cell-autonomous effects of cannabinoid receptor activation on neurite growth, the team is strongly motivated to investigate the physiological and possible pathophysiological roles of these effects.

Figure 2

Fig 2 : After synthesis, receptors are first delivered to the somatodendritic plasma membrane. From here they are endocytosed due to their constitutive activation and enter a specific transcytotic route (orange). Receptor arriving through this indirect route outnumber directly delivered CB1Rs (blue)

Cannabinoids contract neurons

We have recently identified the contraction of the neuronal actomyosin cytoskeleton as a mechanism conveying a wide-ranging inhibitory role for cannabinoids in neuronal expansion and growth (Roland et al., eLife, 2014).

This mechanism acts downstream of cannabinoid receptor CB1R, the major brain target of endocannabinoids and marijuana, atypically coupled to G12/G13 proteins and the Rho-associated kinase ROCK.

Such modulation of the neural actomyosin cytoskeleton has not yet been reported downstream of neurotransmitter GPCRs. Therefore our results open previously unexpected perspectives in the study and comprehension of brain function.

Fig 3 : Axonal growth-cone, expressing CB1 cannabinoid receptors (blue) and two markers of the cytoskeleton: microtubules are labeled in green and filamentous actin is labeled in red. Microphotography by Alexandre B. Roland

Our tools

Established techniques in the team range from molecular constructions (such as GFP-tagged proteins) through imaging-based measurements of GPCR signaling and traffic in standard cell lines (such as HEK293, CHO), in cultured hippocampal neurons and in utero electroporated organotypic brain slices.

We have also validated recently a novel paradigm of functional brain imaging, in collaboration with Dr Mickael Tanter, Institut Langevin, ESPCI-ParisTech.

This method, called ultrafast Functional Ultrason or fUS, through achieving parallel measurement of functional parameters with sensitivity, spatiotemporal resolution and operating simplicity unmatched by current imaging modalities, will open access to previously unexplored aspects of brain function.

Taking advantage of the specific research environment of ESPCI-ParisTech, one of the leading French "Grandes Ecoles", our specialty is the development and systematic use of quantitative imaging approaches to unravel neuronal function at the cellular level. My initial training in neuroanatomy in the laboratory of M. Palkovits (Semmelweis University, Budapest) enables and strongly motivates me to verify the in vivo relevance of the in vitro results by using transgenic Drosophila and mouse models.

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See also...

Team

Zsolt LENKEÏ, Research Director at INSERM, is head of the Dynamique et Structure Neuronale. Researcher and Lecturer Zsolt LENKEÏ Research (...) 

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Publications

Out-of-focus background subtraction for fast structured illumination super-resolution microscopy of optically thick samples. Vermeulen P, Zhan H, (...) 

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Practical information

Unit Director
Thomas Preat
thomas.preat (arobase) espci.fr

Administrator chief
Stéphanie Ledoux
stephanie.ledoux (arobase) espci.fr

Administrator
Tu-Khanh Nguyen
tu-khanh.nguyen (arobase) espci.fr

Phone : +33 (0) 1 40 79 43 02

To contact us