Carbon metabolism intermediates are known to be fundamental precursors in the biosynthesis of carbohydrates and lipids, whose metabolism is being increasingly acknowledged as a relevant lifespan regulator. Therefore, to understand the importance of these compounds in the context of aging, it is necessary to deepen the relations among the pathways involved in the production of metabolic precursors and how fluxes of single key metabolites impact on cellular survival. In order to reach this goal, we employ the budding yeast Saccharomyces cerevisiae, a model organism successfully used to study evolutionarily conserved molecular mechanisms. In particular, the interest is in chronological aging, defined as the aging process of quiescent yeast cells during the stationary phase, that is, after all carbon sources are consumed. Currently, this model is extensively used as a paradigm for the aging process of mammalian post-mitotic cells such as neurons and myocytes. In this context, a particularly interesting metabolite is acetyl-CoA, the activated form of acetate due to a thioester bond with coenzyme A. Acetyl-CoA is indeed important for many cellular events, depending on its cellular localization. For instance, mitochondrial acetyl-CoA, generated from the uptake of pyruvate in the mitochondria, enters the TCA cycle and fosters both biosynthesis and energy metabolism. The other great distinct pool, represented by the nucleocytoplasmic acetyl-CoA, provides instead the fundamental bricks for the biosynthesis of lipid macromolecules, including fatty acids, which in turn, if processed by β-oxidation, can provide again acetyl-CoA. In addition, the available nucleocytosolic pool is also used as a source of acetyl groups to modulate, through post-translational modifications, enzyme activities and chromatin state, therefore the functional state of a cell. Proceeding through steps, three key points become relevant in the context of acetyl-CoA and aging: 1) the regulation of the flux of acetyl-CoA precursors among compartments; 2) the control of metabolism through (de)acetylation; 3) the role of fatty acid metabolism, intimately linked to acetyl-CoA. These key points were investigated generating ad hoc mutants through gene deletion, analysing different metabolic and functional aspects and using peculiar nutritional approaches. Overall, results gave insights on the role of acetyl-CoA, highlighting that the importance of this metabolite is not restricted to a particular growth phase or metabolism but has a broader value. A correct production and distribution of acetyl-CoA among compartments, supported by the administration of nutritionally relevant molecules, guarantees an efficient modulation of metabolism with the contribute of post-translational modifications, increasing longevity. Also, mitochondria emerged as extremely sensitive on how acetyl-CoA is managed during aging, therefore as sensors to monitor the cellular state through time. In conclusion, the obtained data underline the complexity of acetyl-CoA metabolism during aging, and how the management of this key metabolite is strictly related to cellular survival.

I composti intermedi generati dal metabolismo del carbonio sono precursori fondamentali per la biosintesi di lipidi e carboidrati, la cui importanza nella regolazione della longevità è sempre più rilevante. Per comprendere il ruolo di tali composti nel contesto dell’invecchiamento diventa necessario indagare le relazioni tra i pathway che generano i precursori metabolici e come i flussi dei singoli metaboliti impattano sulla sopravvivenza cellulare. Per affrontare questa tematica, il mio progetto di dottorato sfrutta il lievito gemmante Saccharomyces cerevisiae, organismo modello ampiamente affermato per lo studio di meccanismi molecolari evolutivamente conservati. In particolare, si è studiato l’invecchiamento cronologico, ossia quello a cui vanno incontro cellule di lievito quiescenti in fase stazionaria e che rappresenta un efficace modello per lo studio dell’invecchiamento di cellule di mammifero post-mitotiche quali neuroni e miociti. In questo contesto, un metabolita di fondamentale interesse è l’acetil-CoA, ossia la forma attivata dell’acetato tramite un legame tioestere con il coenzima A. L’acetil-CoA rappresenta un importante snodo per il metabolismo, anche in relazione alla sua localizzazione. Ad esempio, l’acetil-CoA mitocondriale, generato per decarbossilazione ossidativa del piruvato nel mitocondrio, entra nel TCA per foraggiare il metabolismo biosintetico e quello energetico. L’altro grande pool di acetil-CoA è quello nucleocitosolico, rilevante nel metabolismo lipidico: l’acetil-CoA può essere infatti utilizzato per convogliare unità di carbonio alla biosintesi di macromolecole lipidiche, inclusi acidi grassi i quali in seguito, tramite β-ossidazione nei perossisomi, possono fornire nuovamente acetil-CoA. Inoltre, lo stesso pool nucleocitosolico è anche usato come donatore di gruppi acetili, per regolare tramite l’acetilazione attività enzimatiche e stato della cromatina, quindi lo stato funzionale della cellula. Procedendo, tre punti diventano rilevanti: 1) la regolazione del flusso dei precursori dell'acetil-CoA tra compartimenti cellulari; 2) il controllo del metabolismo attraverso il meccanismo di (de)acetilazione; 3) il ruolo degli acidi grassi, intimamente connessi con l’acetil-CoA. Questi punti sono stati indagati generando mutanti ad hoc tramite la delezione di geni, esaminando diversi aspetti sia metabolici che funzionali e adoperando approcci nutrizionali mirati. Complessivamente, i risultati hanno permesso chiarire come il ruolo dell’acetil-CoA non sia rilegato ad una specifica fase di crescita o ad un particolare metabolismo ma abbia un valore più ampio. La sua corretta produzione e distribuzione tra i compartimenti cellulari, favorita anche dalla somministrazione di molecole di interesse nutrizionale, garantisce una modulazione efficace del metabolismo anche attraverso modificazioni post-traduzionali, incrementando la longevità cellulare. Infine, i mitocondri sono emersi come organelli estremamente sensibili alla gestione di acetil-CoA, quindi come sensori per monitorare lo stato cellulare nel tempo. In conclusione, i dati ottenuti sottolineano la complessità del metabolismo dell’acetil-CoA durante l’invecchiamento, e come la gestione di questo metabolita chiave sia strettamente legata alla sopravvivenza cellulare.

(2017). Acetyl-CoA Metabolism and Aging: Risks and Resources. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2017).

Acetyl-CoA Metabolism and Aging: Risks and Resources

PELLEGRINO COPPOLA, DAMIANO
2017

Abstract

Carbon metabolism intermediates are known to be fundamental precursors in the biosynthesis of carbohydrates and lipids, whose metabolism is being increasingly acknowledged as a relevant lifespan regulator. Therefore, to understand the importance of these compounds in the context of aging, it is necessary to deepen the relations among the pathways involved in the production of metabolic precursors and how fluxes of single key metabolites impact on cellular survival. In order to reach this goal, we employ the budding yeast Saccharomyces cerevisiae, a model organism successfully used to study evolutionarily conserved molecular mechanisms. In particular, the interest is in chronological aging, defined as the aging process of quiescent yeast cells during the stationary phase, that is, after all carbon sources are consumed. Currently, this model is extensively used as a paradigm for the aging process of mammalian post-mitotic cells such as neurons and myocytes. In this context, a particularly interesting metabolite is acetyl-CoA, the activated form of acetate due to a thioester bond with coenzyme A. Acetyl-CoA is indeed important for many cellular events, depending on its cellular localization. For instance, mitochondrial acetyl-CoA, generated from the uptake of pyruvate in the mitochondria, enters the TCA cycle and fosters both biosynthesis and energy metabolism. The other great distinct pool, represented by the nucleocytoplasmic acetyl-CoA, provides instead the fundamental bricks for the biosynthesis of lipid macromolecules, including fatty acids, which in turn, if processed by β-oxidation, can provide again acetyl-CoA. In addition, the available nucleocytosolic pool is also used as a source of acetyl groups to modulate, through post-translational modifications, enzyme activities and chromatin state, therefore the functional state of a cell. Proceeding through steps, three key points become relevant in the context of acetyl-CoA and aging: 1) the regulation of the flux of acetyl-CoA precursors among compartments; 2) the control of metabolism through (de)acetylation; 3) the role of fatty acid metabolism, intimately linked to acetyl-CoA. These key points were investigated generating ad hoc mutants through gene deletion, analysing different metabolic and functional aspects and using peculiar nutritional approaches. Overall, results gave insights on the role of acetyl-CoA, highlighting that the importance of this metabolite is not restricted to a particular growth phase or metabolism but has a broader value. A correct production and distribution of acetyl-CoA among compartments, supported by the administration of nutritionally relevant molecules, guarantees an efficient modulation of metabolism with the contribute of post-translational modifications, increasing longevity. Also, mitochondria emerged as extremely sensitive on how acetyl-CoA is managed during aging, therefore as sensors to monitor the cellular state through time. In conclusion, the obtained data underline the complexity of acetyl-CoA metabolism during aging, and how the management of this key metabolite is strictly related to cellular survival.
ORLANDI, IVAN
yeast,; aging,; acetyl-CoA,; metabolism,; mitochondria
yeast,; aging,; acetyl-CoA,; metabolism,; mitochondria
BIO/10 - BIOCHIMICA
English
26-apr-2017
SCIENZE DELLA VITA - 81R
29
2015/2016
open
(2017). Acetyl-CoA Metabolism and Aging: Risks and Resources. (Tesi di dottorato, Università degli Studi di Milano-Bicocca, 2017).
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/10281/158274
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