Neurochemical Research

, Volume 33, Issue 8, pp 1459–1465 | Cite as

Post-translational Regulation of l-Glutamic Acid Decarboxylase in the Brain

Original Paper


Gamma-aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the central nervous system. GABA is converted from glutamic acid by the action of glutamic acid decarboxylase (GAD). There are two forms of GAD in the brain, GAD65 and GAD67, referring to a molecular weight of 65 and 67 kDa, respectively. Perturbations in GABAergic neurotransmission have been linked to a number of neurological disorders. Since GAD is the rate-limiting enzyme in controlling GABA synthesis, it is important to understand how GAD is regulated in the brain. It is known that GAD function can be regulated at the transcriptional/translational and post-translational levels. This review focuses briefly on the recent advances in revealing the post-translational regulation of GAD function including protein phosphorylation, palmitoylation and activity-dependent cleavage. The results from these studies have improved our understanding of the regulation of GAD function in the brain.


Post-translational modification GAD65 GAD67 Phosphorylation Truncated GAD Calpain Palmitoylation 



Cysteine string protein


Glutamic acid decarboxylase


Huntingtin interacting protein 14


Heat shock protein 70


Insulin-dependent diabetes mellitus


Palmitoyl acyltransferase


Protein palmitoyl thioesterase


Stiff person syndrome


Synaptic vesicles


Vesicular GABA transporter



This work was supported by the National Institutes of Health (NS37851 to J-Y Wu).


  1. 1.
    Bu DF, Erlander MG, Hitz BC et al (1992) Two human glutamate decarboxylases, 65-kDa GAD and 67-kDa GAD, are each encoded by a single gene. Proc Natl Acad Sci USA 89:2115–2119PubMedCrossRefGoogle Scholar
  2. 2.
    Tian N, Petersen C, Kash S et al (1999) The role of the synthetic enzyme GAD65 in the control of neuronal gamma-aminobutyric acid release. Proc Natl Acad Sci USA 96:12911–12916PubMedCrossRefGoogle Scholar
  3. 3.
    Kaufman DL, Houser CR, Tobin A (1991) Two forms of the aminobutyric acid synthetic enzyme glutamate decarboxylase have distinct intraneuronal distribution and cofactor interaction. J Neurochem 56:720–723PubMedCrossRefGoogle Scholar
  4. 4.
    Owens D, Kriegstein A (2002) Is there more to GABA than synaptic inhibition? Nat Rev Neurosci 3:715–727PubMedCrossRefGoogle Scholar
  5. 5.
    Fenalti G, Law RH, Buckle AM et al (2007) GABA production by glutamic acid decarboxylase is regulated by a dynamic catalytic loop. Nat Struct Mol Biol 14:280–286PubMedCrossRefGoogle Scholar
  6. 6.
    Asada H, Kawamura Y, Maruyama K et al (1997) Cleft palate and decreased brain gamma-aminobutyric acid in mice lacking the 67-kDa isoform of glutamic acid decarboxylase. Proc Natl Acad Sci USA 94:6496–6499PubMedCrossRefGoogle Scholar
  7. 7.
    Asada H, Kawamura Y, Maruyama K et al (1996) Mice lacking the 65 kDa isoform of glutamic acid decarboxylase (GAD65) maintain normal levels of GAD67 and GABA in their brains but are susceptible to seizures. Biochem Biophys Res Commun 229:891–895PubMedCrossRefGoogle Scholar
  8. 8.
    Hsu CC, Davis KM, Jin H et al (2000) Association of l-glutamic acid decarboxylase to the 70-kDa heat shock protein as a potential anchoring mechanism to synaptic vesicles. J Biol Chem 275:20822–20828PubMedCrossRefGoogle Scholar
  9. 9.
    Jin H, Wu H, Osterhaus G et al (2003) Demonstration of functional coupling between gamma-aminobutyric acid (GABA) synthesis and vesicular GABA transport into synaptic vesicles. Proc Natl Acad Sci USA 100:4293–4298PubMedCrossRefGoogle Scholar
  10. 10.
    Tian N, Petersen C, Kash S et al (1999) The role of the synthetic enzyme GAD65 in the control of neuronal gamma-aminobutyric acid release. Proc Natl Acad Sci USA 96:12911–12916PubMedCrossRefGoogle Scholar
  11. 11.
    Luo J, Kaplitt MG, Fitzsimons HL et al (2002) Subthalamic GAD gene therapy in a Parkinson’s disease rat model. Science 298:425–429PubMedCrossRefGoogle Scholar
  12. 12.
    Deng YP, Albin RL, Penney JB et al (2004) Differential loss of striatal projection systems in Huntington’s disease: a quantitative immunohistochemical study. J Chem Neuroanat 27:143–164PubMedCrossRefGoogle Scholar
  13. 13.
    Soghomonian JJ, Laprade N (1997) Glutamate decarboxylase (GAD67 and GAD65) gene expression is increased in a subpopulation of neurons in the putamen of Parkinsonian monkeys. Synapse 27:122–132PubMedCrossRefGoogle Scholar
  14. 14.
    Solimena M, De Camilli P (1991) Autoimmunity to glutamic acid decarboxylase (GAD) in Stiff-Man syndrome and insulin-dependent diabetes mellitus. Trends Neurosci 14:452–457PubMedCrossRefGoogle Scholar
  15. 15.
    Chattopadhyay S, Ito M, Cooper JD et al (2002) An autoantibody inhibitory to glutamic acid decarboxylase in the neurodegenerative disorder Batten disease. Hum Mol Gen 11:1421–1431PubMedCrossRefGoogle Scholar
  16. 16.
    Stephenson DT, Li Q, Simmons C et al (2005) Expression of GAD65 and GAD67 immunoreactivity in MPTP-treated monkeys with or without l-DOPA administration. Neurobiol Dis 20:347–359PubMedCrossRefGoogle Scholar
  17. 17.
    Freichel C, Potschka H, Ebert U et al (2006) Acute changes in the neuronal expression of GABA and glutamate decarboxylase isoforms in the rat piriform cortex following status epilepticus. Neuroscience 141:2177–2194PubMedCrossRefGoogle Scholar
  18. 18.
    Guidotti A, Auta J, Davis JM et al (2000) Decrease in reelin and glutamic acid decarboxylase67 (GAD67) expression in schizophrenia and bipolar disorder: a postmortem brain study. Arch Gen Psychiatry 57:1061–1069PubMedCrossRefGoogle Scholar
  19. 19.
    Impagnatiello F, Guidotti AR, Pesold C et al (1998) A decrease of reelin expression as a putative vulnerability factor in schizophrenia. Proc Natl Acad Sci USA 95:15718–15723PubMedCrossRefGoogle Scholar
  20. 20.
    Bao J, Wai Yiu C, Jang-Yen W (1995) Brain l-glutamate decarboxylase: inhibition by phosphorylation and activation by dephosphorylation. J Biol Chem 270:6464–6467PubMedCrossRefGoogle Scholar
  21. 21.
    Hsu CC, Thomas C, Chen W et al (1999) Role of synaptic vesicle proton gradient and protein phosphorylation on ATP-mediated activation of membrane-associated brain glutamate decarboxylase. J Biol Chem 274:24366–24371PubMedCrossRefGoogle Scholar
  22. 22.
    Wei JN, Davis KM, Wu H et al (2004) Protein phosphorylation of human brain glutamic acid decarboxylase (GAD)65 and GAD67 and its physiological implications. Biochemistry 43:6182–6189PubMedCrossRefGoogle Scholar
  23. 23.
    Battaini F, Pascale A (2005) Protein kinase C signal transduction regulation in physiological and pathological aging. Ann NY Acad Sci 1057:177–192PubMedCrossRefGoogle Scholar
  24. 24.
    Khasar SG, Lin YH, Martin A et al (1999) A novel nociceptor signaling pathway revealed in protein kinase C epsilon mutant mice. Neuron 24:253–260PubMedCrossRefGoogle Scholar
  25. 25.
    Saitoh N, Hori T,Takahashi T (2001) Activation of the epsilon isoform of protein kinase C in the mammalian nerve terminal. Proc Natl Acad Sci USA 98:14017–14021PubMedCrossRefGoogle Scholar
  26. 26.
    Pastorino L, Colciaghi F, Gardoni F et al (2000) (+)-MCPG induces PKCepsilon translocation in cortical synaptosomes through a PLD-coupled mGluR. Eur J Neurosci 12:1310–1318PubMedCrossRefGoogle Scholar
  27. 27.
    Choi DS, Wang D, Yu GQ et al (2006) PKCepsilon increases endothelin converting enzyme activity and reduces amyloid plaque pathology in transgenic mice. Proc Natl Acad Sci USA 103:8215–8220PubMedCrossRefGoogle Scholar
  28. 28.
    Prekeris R, Mayhew MW, Cooper JB et al (1996) Identification and localization of an actin-binding motif that is unique to the epsilon isoform of protein kinase C and participates in the regulation of synaptic function. J Cell Biol 132:77–90PubMedCrossRefGoogle Scholar
  29. 29.
    Namchuk M, Lindsay L, Turck CW et al (1997) Phosphorylation of serine residues 3, 6, 10, and 13 distinguishes membrane anchored from soluble glutamic acid decarboxylase 65 and is restricted to glutamic acid decarboxylase 65alpha. J Biol Chem 272:1548–1557PubMedCrossRefGoogle Scholar
  30. 30.
    Dietrich LE, Ungermann C (2004) On the mechanism of protein palmitoylation. EMBO Rep 5:1053–1057PubMedCrossRefGoogle Scholar
  31. 31.
    Greaves J, Chamberlain L (2007) Palmitoylation-dependent protein sorting. J Cell Biol 176:249–254PubMedCrossRefGoogle Scholar
  32. 32.
    Huang K, Yanai A, Kang R et al (2004) Huntingtin-interacting protein HIP14 is a palmitoyl transferase involved in palmitoylation and trafficking of multiple neuronal proteins. Neuron 44:977–986PubMedCrossRefGoogle Scholar
  33. 33.
    el-Husseini Ael D, Bredt D (2002) Protein palmitoylation: a regulator of neuronal development and function. Nat Rev Neurosci 3:791–802CrossRefGoogle Scholar
  34. 34.
    Kanaani J, Diacovo MJ, El-Husseini Ael D et al (2004) Palmitoylation controls trafficking of GAD65 from Golgi membranes to axon-specific endosomes and a Rab5a-dependent pathway to presynaptic clusters. J Cell Sci 117:2001–2013PubMedCrossRefGoogle Scholar
  35. 35.
    Kanaani J, El-Husseini Ael D, Aguilera-Moreno A et al (2002) A combination of three distinct trafficking signals mediates axonal targeting and presynaptic clustering of GAD65. J Cell Biol 158:1229–1238PubMedCrossRefGoogle Scholar
  36. 36.
    Smotrys JE, Linder ME (2004) Palmitoylation of intracellular signaling proteins: regulation and function. Annu Rev Biochem 73:559–587PubMedCrossRefGoogle Scholar
  37. 37.
    Bond RW, Wyborski RJ, Gottlieb D (1990) Developmentally regulated expression of an exon containing a stop codon in the gene for glutamic acid decarboxylase. Proc Natl Acad Sci USA 87:8771–8775PubMedCrossRefGoogle Scholar
  38. 38.
    Szabo G, Katarova Z,Greenspan R (1994) Distinct protein forms are produced from alternatively spliced bicistronic glutamic acid decarboxylase mRNAs during development. Mol Cell Biol 14:7535–7545PubMedGoogle Scholar
  39. 39.
    Connaughton VP, Dyer KD, Nadi NS et al (2001) The expression of GAD67 isoforms in zebrafish retinal tissue changes over the light/dark cycle. J Neurocytol 30:303–312PubMedCrossRefGoogle Scholar
  40. 40.
    Buss K, Drewke C, Lohmann S et al (2001) Properties and interaction of heterologously expressed glutamate decarboxylase isoenzymes GAD(65 kDa) and GAD(67 kDa) from human brain with ginkgotoxin and its 5′-phosphate. J Med Chem 44:3166–3174PubMedCrossRefGoogle Scholar
  41. 41.
    Wei J, Jin Y, Wu H et al (2003) Identification and functional analysis of truncated human glutamic acid decarboxylase 65. J Biomed Sci 10:617–624PubMedCrossRefGoogle Scholar
  42. 42.
    Christgau S, Aanstoot HJ, Schierbeck H et al (1992) Membrane anchoring of the autoantigen GAD65 to microvesicles in pancreatic beta-cells by palmitoylation in the NH2-terminal domain. J Cell Biol 118:309–320PubMedCrossRefGoogle Scholar
  43. 43.
    Wei J, Lin CH, Wu H et al (2006) Activity-dependent cleavage of brain glutamic acid decarboxylase 65 by calpain. J Neurochem 98:1688–1695PubMedCrossRefGoogle Scholar
  44. 44.
    Goll DE, Thompson VF, Li H et al (2003) The calpain system. Physiol Rev 83:731–801PubMedGoogle Scholar
  45. 45.
    Wu HY, Lynch D (2006) Calpain and synaptic function. Mol Neurobiol 33:215–236PubMedCrossRefGoogle Scholar
  46. 46.
    Branca D (2004) Calpain-related diseases. Biochem Biophys Res Commun 322:1098–1104PubMedCrossRefGoogle Scholar
  47. 47.
    Nixon R (2003) The calpains in aging and aging-related diseases. Aging Res Rev 2:407–418CrossRefGoogle Scholar
  48. 48.
    Lee MS, Kwon YT, Li M et al (2000) Neurotoxicity induces cleavage of p35 to p25 by calpain. Nature 405:360–364PubMedCrossRefGoogle Scholar
  49. 49.
    Raynaud F, Marcilhac A (2006) Implication of calpain in neuronal apoptosis. A possible regulation of Alzheimer’s disease. FEBS J 273:3437–3443PubMedCrossRefGoogle Scholar
  50. 50.
    Crocker SJ, Smith PD, Jackson-Lewis V et al (2003) Inhibition of calpains prevents neuronal and behavioral deficits in an MPTP mouse model of Parkinson’s disease. J Neurosci 23:4081–4091PubMedGoogle Scholar
  51. 51.
    Baekkeskov S, Aanstoot HJ, Christgau S et al (1990) Identification of the 64 K autoantigen in insulin-dependent diabetes as the GABA-synthesizing enzyme glutamic acid decarboxylase. Nature 347:151–156PubMedCrossRefGoogle Scholar
  52. 52.
    Lohmann T, Hawa M, Leslie RD et al (2000) Immune reactivity to glutamic acid decarboxylase 65 in stiffman syndrome and type 1 diabetes mellitus. Lancet 356:31–35PubMedCrossRefGoogle Scholar
  53. 53.
    Raju R, Foote J, Banga JP et al (2005) Analysis of GAD65 autoantibodies in Stiff-Person syndrome patients. J Immunol 175:7755–7762PubMedGoogle Scholar
  54. 54.
    Kim J, Namchuk M, Bugawan T et al (1994) Higher autoantibody levels and recognition of a linear NH2-terminal epitope in the autoantigen GAD65, distinguish stiff-man syndrome from insulin-dependent diabetes mellitus. J Exp Med 180:595–606PubMedCrossRefGoogle Scholar
  55. 55.
    Lich JD, Elliott JF,Blum J (2000) Cytoplasmic processing is a prerequisite for presentation of an endogenous antigen by major histocompatibility complex class II proteins. J Exp Med 191:1513–1524PubMedCrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC 2008

Authors and Affiliations

  1. 1.Department of Basic Science, Charles E. Schmidt College of Biomedical ScienceFlorida Atlantic UniversityBoca RatonUSA

Personalised recommendations