Dynamique de la Signalisation Intracellulaire et Cibles Thérapeutiques

Intracellular signals determine the properties of a cell within an organism, and participates in the intregration of extracellular cues leading to an appropriate cellular response. Our approach focuses on the dynamic aspects of this integration process, in particular with the use of real-time biosensor imaging. We use this experimental framework to monitor adaptations in physiopathological conditions and analyze the effects of pharmacological compounds. This will ultimately lead to novel therapeutic strategies.

Trans-differentiation of vascular smooth muscle cells in atherosclerosis

A short splice variant of adenylyl cyclase perturbs cAMP signaling.

Vascular smooth muscle cells submitted to chronic inflammation - such as that involved in athrosclerotic plaque formation or post-angiopalsty restenosis - show a prominent reduction in their cAMP production, leading to increased cell motility and proliferation. We showed that this transdifferentiation depends on the de-novo expression of a short splice variants of adenylyl cyclase 8, which lacks the first 5 transmembrane segments. These short forms of AC8 exert a dominant-negative effect by dimerizing with the other full-length functional adenylyl cyclases, retaining them in the endoplasmic reticulum and thus reducing global cAMP production within the cell.

We are now exploring how to inhibit this deleterious process in the prospect of preventing vascular diseases.

More on the short AC8 isoforms

Biosensor imaging to analyze the dysfunctions in cAMP signaling

Live-imaging of cAMP in primary cultures of control vascular smooth muscle cells (top) and the same cell type after chronic interleukine treatment (bottom). Forskolin was used to increase cAMP production. In control cells, this leads to a maximal response, whereas transdifferentiated cells show a limited cAMP production.

Référence: Vallin et al, 2018.

Dopamine and other neuromodulators in the striatum

A number of neuromodulators, a complex integrating scheme

Medium-sized spiny neurons in the striatum express either D1 or D2 dopamine receptors, coupled in opposite way to the cAMP signaling pathway. Other receptors...

Dynamics of D1 and D2 responses

Dopamine has a similar efficacy on D1 and D2 receptors

Biosensor imaging in striatal brain slices was used to monitor the cAMP response to dopamine, simultaneously in neurons expressing either D1 or D2 dopamine receptors. These receptors, coupled to adenylyl cyclase in opposite ways, trigger symmetric changes in intracellular cAMP.

In contrast to what is commonly accepted in the literature, our experiments show that dopamine has almost the same efficacy on D1 and D2 receptors. Differences in the integration scheme (depending on DARPP-32) are the actual causes of D1/D2 functional difference in responsiveness.

Phosphodiesterases

The main phosphodiesterases expressed in the striatum are PDE1B, PDE2A and PDE10A. They share the feature of degrading both cAMP and cGMP.

Using biosensor imaging, we showed that PDE10A is responsible for controlling baseline cAMP levels, and is efficient on low cAMP concentrations.

We also showed that PDE2A can be efficiently activated by cGMP, and PDE2 controls the higher levels of concentration of both cAMP and cGMP.

We are currently exploring the functional role played by PDE1A.

cAMP signaling during neuronal migration

Newly formed neurons

This project developed through a collaboration with Isabelle Caillé aims at analyzing the transient cAMP signals that occurr in the cytosol of neurons during their migration from the sub-ventricular zone toward the olfactory bulb.

Alterations in cAMP signaling in Alzheimer's disease

Neurons and vessels undergo a coicident degeneration during Alzheimer's disease.