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Étude fonctionnelle de l'AMP-activated protein kinase chez l'huître creuse Crassostrea gigas

Abstract : The objective of this thesis was to characterize elements implicated in the energypathway of the AMP-activated protein kinase of the Pacific oyster Crassostrea gigas. Thecharacterization of the elements was performed in the scope of understanding their involvementin energy management, particularly in response to physiological conditions requiring energy, asreproduction or environmental stress, such as hypoxia or fasting.At genomic level, the three subunits of AMPK trimer and several elements involved inAMPK signaling pathway and in carbohydrate and lipid metabolism, supposedly under AMPKcontrol, were described. Additionally, at proteomic level, several heterologous antibodiestargeting AMPKα subunit isoforms and threonine 172 phosphorylation site of AMPKα subunit,indirect witness of AMPK activity, were assayed. Two truncated α subunits in the kinase domainwere characterized essentially in muscles, suggesting their involvement in muscle function.During a hypoxic stress, a significant increase of truncated α subunits protein amount wasobserved in smooth muscle. These results suggest that, for a period of at least 6 h, thesetruncated subunits are necessary for the maintenance of aerobic metabolism in smooth muscle ofC. gigas, allowing it to fulfill its static closing valves. We suggested that in vivo accumulation oftruncated AMPKα could serve as modulator or as transdominant negative regulator of the fulllengthAMPKα activity. In the gonad, AMPK appeared to be activated through the process ofgametogenesis, in order to support the catabolic processes of gametes creation. During theanabolic phase, when oocyte reserves were created, a signal disruption was observed. Finally,during controlled experiment, a physiological approach by food deprivation and apharmacological approach using AICAR injections were performed to modulate AMPK signal.This analysis showed that neither fasting nor AICAR induced an increase of AMPKphosphorylation, as expected. Although, several changes related to AICAR injection wereobserved in oysters physiology, such as the change of the AMP:ATP ratio in fed oysters and aAICAR dose-related mortality in fasting oysters. AMPK characterization in C. gigas opens newperspectives demanding extensive functional studies to establish the key role of AMPK in energymanagement, as demonstrated in vertebrates’ species, in order to understand the oyster’s energymetabolism.
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Éric Guévélou. Étude fonctionnelle de l'AMP-activated protein kinase chez l'huître creuse Crassostrea gigas. Biologie animale. Université de Bretagne occidentale - Brest, 2012. Français. ⟨NNT : 2012BRES0031⟩. ⟨tel-00863226⟩

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