L'AMPK est un senseur cellulaire des réserves énergétiques de l’organisme. Les spermatozoïdes, mobilisent beaucoup d’énergie pour leur mobilité et la fécondation de l’ovocyte. L’objectif de ce travail était de caractériser et décrire des éléments clés de la voie de signalisation de l'AMPK, de comprendre leur implication dans les spermatozoïdes de coq et d’étudier comment leurs modulateurs peuvent impacter les fonctions des gamètes conservés in vitro. Nous avons montré une augmentation de la mobilité et de la réaction acrosomique dans les spermatozoïdes exposés à l'AICAR et à la metformine, des activateur de l’AMPK, y compris après avoir été congelés. Ces activateurs ont partiellement restauré les activités des enzymes antioxydantes (SOD, GPx, GR): et diminué les ROS et la LPO dans les spermatozoïdes décongelés. Nous avons établi la présence des CaMKKs (α et β) et de CaMKI dans les spermatozoïdes et leur rôle lié au calcium extracellulaire (via les canaux calcique SOCs) dans la voie de régulation de l'AMPK et dans la mobilité et la réaction acrosomique des spermatozoïdes. En conclusion, ce travail confirme le rôle de différents acteurs de signalisation liés au métabolisme énergétique et aux flux calciques dans les fonctions des spermatozoïdes. / AMPK is a cellular sensor of body energy reserves. Spermatozoa mobilize a lot of energy for their motility and the fertilization of the oocyte. The objective of this work was to characterize and describe key elements of the signaling pathway of AMPK, understand their involvement in chicken spermatozoa and study how their modulators may impact the functions of in vitro preserved gametes. We showed an increase in mobility and acrosome reaction in spermatozoa exposed to AICAR and metformin, activators of AMPK, including after freezing. These activators have partially restored the activities of antioxidant enzymes (SOD, GPx, GR): and decreased ROS and LPO in thawed spermatozoa. We have established the presence of CaMKKs (α and β) and CaMKI in sperm and their role related to extracellular calcium (via calcium channels SOCs) in the control channel of AMPK and in motility and acrosome reaction of spermatozoa. In conclusion, this work confirms the role of different signaling actors related to energy metabolism and calcium fluxes in spermatozoa functions.

<p>Multifunctional calcium/calmodulin dependent protein kinases (CaMKs) are key regulators of spine structural plasticity and long-term potentiation (LTP) in neurons. CaMKs have promiscuous and overlapping substrate recognition motifs, and are distinguished in their regulatory role based on differences in the spatiotemporal dynamics of activity. While the function and activity of CaMKII in synaptic plasticity has been extensively studied, that of CaMKI, another major class of CaMK required for LTP, still remain elusive. </p><p>Here, we develop a Förster’s Resonance Energy Transfer (FRET) based sensor to measure the spatiotemporal activity dynamics of CaMK1. We monitored CaMKI activity using 2-photon fluorescence lifetime imaging, while inducing LTP in single dendritic spines of rat (Rattus Norvegicus, strain Sprague Dawley) hippocampal CA1 pyramidal neurons using 2-photon glutamate uncaging. Using RNA-interference and pharmacological means, we also characterize the role of CaMKI during spine structural plasticity. </p><p>We found that CaMKI was rapidly and transiently activated with a rise time of ~0.3 s and decay time of ~1 s in response to each uncaging pulse. Activity of CaMKI spread out of the spine. Phosphorylation of CaMKI by CaMKK was required for this spreading and for the initial phase of structural LTP. Combined with previous data showing that CaMKII is restricted to the stimulated spine and required for long-term maintenance of structural LTP, these results suggest that CaMK diversity allows the same incoming signal – calcium – to independently regulate distinct phases of LTP by activating different CaMKs with distinct spatiotemporal dynamics.</p> / Dissertation