1
|
Plaitakis A, Sidiropoulou K, Kotzamani D, Litso I, Zaganas I, Spanaki C. Evolution of Glutamate Metabolism via GLUD2 Enhances Lactate-Dependent Synaptic Plasticity and Complex Cognition. Int J Mol Sci 2024; 25:5297. [PMID: 38791334 PMCID: PMC11120665 DOI: 10.3390/ijms25105297] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 05/07/2024] [Accepted: 05/09/2024] [Indexed: 05/26/2024] Open
Abstract
Human evolution is characterized by rapid brain enlargement and the emergence of unique cognitive abilities. Besides its distinctive cytoarchitectural organization and extensive inter-neuronal connectivity, the human brain is also defined by high rates of synaptic, mainly glutamatergic, transmission, and energy utilization. While these adaptations' origins remain elusive, evolutionary changes occurred in synaptic glutamate metabolism in the common ancestor of humans and apes via the emergence of GLUD2, a gene encoding the human glutamate dehydrogenase 2 (hGDH2) isoenzyme. Driven by positive selection, hGDH2 became adapted to function upon intense excitatory firing, a process central to the long-term strengthening of synaptic connections. It also gained expression in brain astrocytes and cortical pyramidal neurons, including the CA1-CA3 hippocampal cells, neurons crucial to cognition. In mice transgenic for GLUD2, theta-burst-evoked long-term potentiation (LTP) is markedly enhanced in hippocampal CA3-CA1 synapses, with patch-clamp recordings from CA1 pyramidal neurons revealing increased sNMDA receptor currents. D-lactate blocked LTP enhancement, implying that glutamate metabolism via hGDH2 potentiates L-lactate-dependent glia-neuron interaction, a process essential to memory consolidation. The transgenic (Tg) mice exhibited increased dendritic spine density/synaptogenesis in the hippocampus and improved complex cognitive functions. Hence, enhancement of neuron-glia communication, via GLUD2 evolution, likely contributed to human cognitive advancement by potentiating synaptic plasticity and inter-neuronal connectivity.
Collapse
Affiliation(s)
- Andreas Plaitakis
- Department of Neurology, School of Health Sciences, Faculty of Medicine, University of Crete, Voutes, 71003 Heraklion, Crete, Greece; (D.K.); (I.L.); (I.Z.)
| | - Kyriaki Sidiropoulou
- Department of Biology, University of Crete, Voutes, 71003 Heraklion, Crete, Greece;
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology Hellas (IMBB-FORTH), 70013 Heraklion, Crete, Greece
| | - Dimitra Kotzamani
- Department of Neurology, School of Health Sciences, Faculty of Medicine, University of Crete, Voutes, 71003 Heraklion, Crete, Greece; (D.K.); (I.L.); (I.Z.)
| | - Ionela Litso
- Department of Neurology, School of Health Sciences, Faculty of Medicine, University of Crete, Voutes, 71003 Heraklion, Crete, Greece; (D.K.); (I.L.); (I.Z.)
| | - Ioannis Zaganas
- Department of Neurology, School of Health Sciences, Faculty of Medicine, University of Crete, Voutes, 71003 Heraklion, Crete, Greece; (D.K.); (I.L.); (I.Z.)
- Neurology Department, PaGNI University General Hospital of Heraklion, 71500 Heraklion, Crete, Greece
| | - Cleanthe Spanaki
- Department of Neurology, School of Health Sciences, Faculty of Medicine, University of Crete, Voutes, 71003 Heraklion, Crete, Greece; (D.K.); (I.L.); (I.Z.)
- Neurology Department, PaGNI University General Hospital of Heraklion, 71500 Heraklion, Crete, Greece
| |
Collapse
|
2
|
Litso I, Plaitakis A, Fadouloglou VE, Providaki M, Kokkinidis M, Zaganas I. Structural Evolution of Primate Glutamate Dehydrogenase 2 as Revealed by In Silico Predictions and Experimentally Determined Structures. Biomolecules 2023; 14:22. [PMID: 38254622 PMCID: PMC10812971 DOI: 10.3390/biom14010022] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 11/29/2023] [Accepted: 12/04/2023] [Indexed: 01/24/2024] Open
Abstract
Glutamate dehydrogenase (GDH) interconverts glutamate to a-ketoglutarate and ammonia, interconnecting amino acid and carbohydrate metabolism. In humans, two functional GDH genes, GLUD1 and GLUD2, encode for hGDH1 and hGDH2, respectively. GLUD2 evolved from retrotransposition of the GLUD1 gene in the common ancestor of modern apes. These two isoenzymes are involved in the pathophysiology of human metabolic, neoplastic, and neurodegenerative disorders. The 3D structures of hGDH1 and hGDH2 have been experimentally determined; however, no information is available about the path of GDH2 structure changes during primate evolution. Here, we compare the structures predicted by the AlphaFold Colab method for the GDH2 enzyme of modern apes and their extinct primate ancestors. Also, we analyze the individual effect of amino acid substitutions emerging during primate evolution. Our most important finding is that the predicted structure of GDH2 in the common ancestor of apes was the steppingstone for the structural evolution of primate GDH2s. Two changes with a strong functional impact occurring at the first evolutionary step, Arg443Ser and Gly456Ala, had a destabilizing and stabilizing effect, respectively, making this step the most important one. Subsequently, GDH2 underwent additional modifications that fine-tuned its enzymatic properties to adapt to the functional needs of modern-day primate tissues.
Collapse
Affiliation(s)
- Ionela Litso
- Neurology/Neurogenetics Laboratory, School of Medicine, University of Crete, Voutes, 71003 Heraklion, Greece; (I.L.); (A.P.)
| | - Andreas Plaitakis
- Neurology/Neurogenetics Laboratory, School of Medicine, University of Crete, Voutes, 71003 Heraklion, Greece; (I.L.); (A.P.)
| | - Vasiliki E. Fadouloglou
- Department of Molecular Biology and Genetics, Faculty of Health Sciences, Democritus University of Thrace, 68100 Alexandroupolis, Greece;
| | - Mary Providaki
- Institute of Molecular Biology and Biotechnology, Foundation of Research and Technology-Hellas, 70013 Heraklion, Greece; (M.P.); (M.K.)
| | - Michael Kokkinidis
- Institute of Molecular Biology and Biotechnology, Foundation of Research and Technology-Hellas, 70013 Heraklion, Greece; (M.P.); (M.K.)
- Department of Biology, University of Crete, Vasilika Vouton, 71409 Heraklion, Greece
| | - Ioannis Zaganas
- Neurology/Neurogenetics Laboratory, School of Medicine, University of Crete, Voutes, 71003 Heraklion, Greece; (I.L.); (A.P.)
| |
Collapse
|
3
|
The Odyssey of a Young Gene: Structure–Function Studies in Human Glutamate Dehydrogenases Reveal Evolutionary-Acquired Complex Allosteric Regulation Mechanisms. Neurochem Res 2014; 39:471-86. [DOI: 10.1007/s11064-014-1251-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2013] [Revised: 01/24/2014] [Accepted: 01/29/2014] [Indexed: 01/13/2023]
|
4
|
The human GLUD2 glutamate dehydrogenase: localization and functional aspects. Neurochem Int 2009; 55:52-63. [PMID: 19428807 DOI: 10.1016/j.neuint.2009.03.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Revised: 03/02/2009] [Accepted: 03/04/2009] [Indexed: 10/21/2022]
Abstract
In all mammals, glutamate dehydrogenase (GDH), an enzyme central to the metabolism of glutamate, is encoded by a single gene (GLUD1 in humans) which is expressed widely (housekeeping). Humans and other primates also possess a second gene, GLUD2, which encodes a highly homologous GDH isoenzyme (hGDH2) expressed predominantly in retina, brain and testis. There is evidence that GLUD1 was retro-posed <23 million years ago to the X chromosome, where it gave rise to GLUD2 through random mutations and natural selection. These mutations provided the novel enzyme with unique properties thought to facilitate its function in the particular milieu of the nervous system. hGDH2, having been dissociated from GTP control (through the Gly456Ala change), is mainly regulated by rising levels of ADP/l-leucine. To achieve full-range regulation by these activators, hGDH2 needs to set its basal activity at low levels (<10% of full capacity), a property largely conferred by the evolutionary Arg443Ser change. Studies of structure/function relationships have identified residues in the regulatory domain of hGDH2 that modify basal catalytic activity and regulation. In addition, enzyme concentration and buffer ionic strength can influence basal enzyme activity. While mature hGDH1 and hGDH2 isoproteins are highly homologous, their predicted leader peptide sequences show a greater degree of divergence. Study of the subcellular sites targeted by hGDH2 in three different cultured cell lines using a GLUD2/EGFP construct revealed that hGDH2 localizes mainly to mitochondria and to a lesser extent to the endoplasmic reticulum of these cells. The implications of these findings for the potential role of this enzyme in the biology of the nervous system in health and disease are discussed.
Collapse
|