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Binding of antibodies in sera from Type 1 (insulin-dependent) diabetic patients to glutamate decarboxylase from rat tissues. Evidence for antigenic and non-antigenic forms of the enzyme


An islet protein of Mr 64000, identified as the γ-amino butyric acid (GABA)-synthesizing enzyme, glutamate decarboxylase, is a major target for antibodies in Type 1 (insulin-dependent) diabetes mellitus. This enzyme is also expressed in brain and in some other tissues and may exist in multiple forms. The aim of this study was to determine the ability of antibodies from diabetic patients to recognize glutamate decarboxylase from rat islets, brain and other normal rat tissues. Glutamate decarboxylase was detected at high activity levels in brain and at lower levels in islets, kidney, liver, pituitary gland, thyroid gland, adrenal gland, testis and ovary. The ability of antibodies in sera of diabetic patients to immunoprecipitate enzyme activity from detergent extracts of tissues was determined. Antibodies in sera from diabetic patients were found to bind the enzyme from islet and brain extracts, but bound less than 20% of the activity from other tissues. The ability of antibodies to immunoprecipitate the brain enzyme was significantly correlated with the presence of antibodies to the islet 64 kilodalton antigen. These studies show that the glutamate decarboxylase activity expressed in brain shares antigenic determinants with the islet 64 kilodalton antigen. Isoforms of the enzyme expressed in other nonneuronal tissues may be antigenically distinct and may lack determinants recognized by diabetes-associated antibodies.


  1. 1.

    Eisenbarth GS (1986) Type 1 diabetes. A chronic autoimmune disease. N Engl J Med 314: 1360–1368

    Google Scholar 

  2. 2.

    Baekkeskov S, Nielsen JH, Marner B, Bilde T, Ludvigsson J, Lernmark Å (1982) Autoantibodies in newly diagnosed diabetic children immunoprecipitate human pancreatic islet cell proteins. Nature (Lond) 298: 167–169

    Google Scholar 

  3. 3.

    Christie M, Landin-Olsson M, Sundkvist G, Dahlquist G, Lernmark Å, Baekkeskov S (1988) Antibodies to a Mr-64000 islet cell protein in Swedish children with newly-diagnosed Type 1 (insulin-dependent) diabetes. Diabetologia 31: 597–602

    Google Scholar 

  4. 4.

    Christie MR, Pipeleers DG, Lernmark Å, Baekkeskov S (1990) Cellular and subcellular localization of a Mr-64000 protein autoantigen in insulin-dependent diabetes. J Biol Chem 265: 376–381

    Google Scholar 

  5. 5.

    Christie MR, Vohra G, Champagne P, Daneman D, Delovitch TL (1990) Distinct antibody specificities to a 64-kD islet cell antigen in Type 1 diabetes as revealed by trypsin treatment. J Exp Med 172: 789–794

    Google Scholar 

  6. 6.

    Baekkeskov S, Aanstoot HK, Christgau S et al. (1990) Identification of the 64k antigen in insulin-dependent diabetes as the GABA-synthesizing enzyme glutamic acid decarboxylase. Nature (Lond) 347: 151–156

    Google Scholar 

  7. 7.

    Okada Y, Taniguchi H, Shimada C (1976) High concentration of GABA and high glutamate decarboxylase activity in rat pancreatic islets and human insulinoma. Science 194: 620–622

    Google Scholar 

  8. 8.

    Garry DJ, Sorenson RL, Elde RP, Maley BE, Madsen A (1986) Immunohistochemical colocalization of GABA and insulin in β-cells of rat islet. Diabetes 35: 1090–1095

    Google Scholar 

  9. 9.

    Rorsman P, Berggren P-O, Bokvist K et al. (1989) Glucose inhibition of glucagon secretion involves activation of GABA-A-receptor chloride channels. Nature (Lond) 341: 233–236

    Google Scholar 

  10. 10.

    Whelan DT, Scriver CR, Mohyuddin F (1969) Glutamic acid decarboxylase and gamma-aminobutyric acid in mammalian kidney. Nature (Lond) 224: 916–917

    Google Scholar 

  11. 11.

    Erdö SL, Kiss B (1986) Presence of GABA, glutamate decarboxylase and GABA transaminase in peripheral tissues: a collection of quantitative data. In: Erdö SL, Bowery NG (eds) GABA-ergic mechanisms in the mammalian periphery. Raven Press, New York, pp 35–56

    Google Scholar 

  12. 12.

    Erdö SL, Joo F, Wolff JR (1989) Immunohistochemical localization of glutamate decarboxylase in the rat oviduct and ovary: further evidence for non-neural GABA systems. Cell Tissue Res 255: 431–434

    Google Scholar 

  13. 13.

    Persson H, Pelto-Huikko M, Metsis M et al. (1990) Expression of the neurotransmitter-synthesizing enzyme glutamic acid decarboxylase in male germ cells. Mol Cell Biol 10: 4701–4711

    Google Scholar 

  14. 14.

    Kaufman DL, Houser CR, Tobin AJ (1991) Two forms of the γ-aminobutyric acid synthetic enzyme glutamate decarboxylase have distinct intraneuronal distributions and cofactor interactions. J Neurochem 56: 720–723

    Google Scholar 

  15. 15.

    Spink DC, Porter TG, Wu S, Martin DL (1985) Characterization of three kinetically distinct forms of glutamate decarboxylase from pig brain. Biochem J 231: 695–703

    Google Scholar 

  16. 16.

    Michelsen BK, Petersen JS, Boel E, Moldrup A, Dyrberg T, Madsen OD (1991) Cloning, characterization and autoimmune recognition of rat islet glutamic acid decarboxylase in insulindependent diabetes mellitus. Proc Natl Acac Sci 88: 8754–8758

    Google Scholar 

  17. 17.

    Christgau S, Schierbeck H, Aanstoot H-J et al. (1991) Pancreatic β cells express two autoantigenic forms of glutamic acid decarboxylase, a 64-kDa hydrophilic form and a 64-kDa amphiphilic form which can be both membrane bound and soluble. J Biol Chem 266: 21257–21264

    Google Scholar 

  18. 18.

    Christie MR, Daneman D, Champagne P, Delovitch TL (1990) Persistence of antibodies to 64000-Mr islet cell protein after onset of Type 1 diabetes. Diabetes 39: 653–656

    Google Scholar 

  19. 19.

    Brundstedt J, Nielsen JH, Lernmark Å, Hagedorn Study Group (1984) Isolation of islets from mice and rats. In: Larner J, Pohl S (eds) Methods in diabetes research. Vol I. Laboratory methods, part C. John Wiley and Sons, New York, pp 245–258

    Google Scholar 

  20. 20.

    Gornall AC, Bardawill CJ, David MM (1949) Determination of serum proteins by means of the Biuret Reaction. J Biol Chem 177: 751–756

    Google Scholar 

  21. 21.

    Chang YC, Gottlieb DI (1988) Characterization of the proteins purified with monoclonal antibodies to glutamic acid decarboxylase. J Neurochem 8: 2123–2130

    Google Scholar 

  22. 22.

    Karlsen AK, Hagopian WA, Grubin CE et al. (1991) Cloning and primary structure of a human islet isoform of glutamic acid decarboxylase from chromosome 10. Proc Natl Acad Sci 88: 8337–8341

    Google Scholar 

  23. 23.

    Roberts E, Kuriyama K (1968) Biochemical-physiological correlations in studies of the gamma amino butyric acid system. Brain Res 8: 1–35

    Google Scholar 

  24. 24.

    Reetz A, Solimena M, Matteoli M, Folli F, Takei K, de Camilli P (1991) GABA and pancreatic β-cells: colocalization of glutamic acid decarboxylase (GAD) and GABA with synaptic-like microvesicles suggests their role in GABA storage and secretion. EMBO J 10: 1275–1284

    Google Scholar 

  25. 25.

    Robbins MS, Grouse LH, Sorenson RL, Elde RP (1981) Effect of muscimol on glucose-stimulated somatostatin and insulin release from the isolated, perfused rat pancreas. Diabetes 30: 168–171

    Google Scholar 

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Christie, M.R., Brown, T.J. & Cassidy, D. Binding of antibodies in sera from Type 1 (insulin-dependent) diabetic patients to glutamate decarboxylase from rat tissues. Evidence for antigenic and non-antigenic forms of the enzyme. Diabetologia 35, 380–384 (1992).

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Key words

  • Autoantigens
  • autoantibodies
  • glutamic acid decarboxylase
  • pancreatic islets