TY - JOUR
T1 - Study of structure-function relationships in human glutamate dehydrogenases reveals novel molecular mechanisms for the regulation of the nerve tissue-specific (GLUD2) isoenzyme
AU - Plaitakis, Andreas
AU - Spanaki, Cleanthe
AU - Mastorodemos, Vasilis
AU - Zaganas, Ioannis
N1 - Funding Information:
This work was supported by the Association for Research and Treatment of Neurological Disorders of Crete «Eύ Zήν», a training grant (EPEAEK-Neurosciences) from the Ministry of Education of Greece (to V.M.) and the “Maria Manasaki” award by the University of Crete (to I.Z.). We are grateful to Dr. Micheal Karpusas for performing the structural modeling of the mutations. We also thank Dr. Athanasios Alegakis, Giorgos Vrentzos and Irene Skoula for their help.
PY - 2003
Y1 - 2003
N2 - In mammalian brain, glutamate dehydrogenase (GDH) is located predominantly in astrocytes, where is thought to play a role in transmitter glutamate's metabolism. Human GDH exists in GLUD1 (housekeeping) and GLUD2 (nerve tissue-specific) isoforms, which share all but 15 out of their 505 amino acids. The GLUD1 GDH is potently inhibited by GTP, whereas the GLUD2 enzyme is resistant to this compound. On the other hand, the GLUD2 isoform assumes in the absence of GTP a conformational state associated with little catalytic activity, but it remains amenable to full activation by ADP and/or L-leucine. Site-directed mutagenesis of the GLUD1 gene at sites that differ from the corresponding residues of the GLUD2 gene showed that replacement of Gly456 by Ala made the enzyme resistant to GTP (IC50=2.8±0.15μM) compared to the wild-type GDH (IC50=0.19±0.01μM). In addition, substitution of Ser for Arg443 virtually abolished basal activity and rendered the enzyme dependent on ADP for its function. These properties may permit the neural enzyme to be recruited under conditions of low energy charge (high ADP:ATP ratio), similar to those that prevail in synaptic astrocytes during intense glutamatergic transmission. Hence, substitution of Ser for Arg443 and Ala for Gly456 are the main evolutionary changes that led to the adaptation of the GLUD2 GDH to the unique metabolic needs of the nerve tissue.
AB - In mammalian brain, glutamate dehydrogenase (GDH) is located predominantly in astrocytes, where is thought to play a role in transmitter glutamate's metabolism. Human GDH exists in GLUD1 (housekeeping) and GLUD2 (nerve tissue-specific) isoforms, which share all but 15 out of their 505 amino acids. The GLUD1 GDH is potently inhibited by GTP, whereas the GLUD2 enzyme is resistant to this compound. On the other hand, the GLUD2 isoform assumes in the absence of GTP a conformational state associated with little catalytic activity, but it remains amenable to full activation by ADP and/or L-leucine. Site-directed mutagenesis of the GLUD1 gene at sites that differ from the corresponding residues of the GLUD2 gene showed that replacement of Gly456 by Ala made the enzyme resistant to GTP (IC50=2.8±0.15μM) compared to the wild-type GDH (IC50=0.19±0.01μM). In addition, substitution of Ser for Arg443 virtually abolished basal activity and rendered the enzyme dependent on ADP for its function. These properties may permit the neural enzyme to be recruited under conditions of low energy charge (high ADP:ATP ratio), similar to those that prevail in synaptic astrocytes during intense glutamatergic transmission. Hence, substitution of Ser for Arg443 and Ala for Gly456 are the main evolutionary changes that led to the adaptation of the GLUD2 GDH to the unique metabolic needs of the nerve tissue.
KW - Glutamate dehydrogenase
KW - Mutagenesis
KW - Regulation
UR - http://www.scopus.com/inward/record.url?scp=0038403827&partnerID=8YFLogxK
U2 - 10.1016/S0197-0186(03)00028-7
DO - 10.1016/S0197-0186(03)00028-7
M3 - Article
C2 - 12742085
AN - SCOPUS:0038403827
SN - 0197-0186
VL - 43
SP - 401
EP - 410
JO - Neurochemistry International
JF - Neurochemistry International
IS - 4-5
ER -