Cloning, characterization, and autoimmune recognition of rat islet glutamic acid decarboxylase in insulin-dependent diabetes mellitus.
A 64-kDa islet protein is a major autoantigen in insulin-dependent diabetes mellitus (IDDM). Autoantibodies against the 64-kDa protein were recently shown to immunoprecipitate glutamic acid decarboxylase (GAD; L-glutamate 1-carboxy-lyase, EC 4.1.1.15) from brain and from islets. We present evidence that the autoantisera also recognize a hydrophilic islet protein of approximately 67 kDa in addition to the amphiphilic 64-kDa form. We have isolated a full-length rat islet GAD cDNA encoding a hydrophilic 67-kDa protein, which appears to be identical to rat brain 67-kDa GAD. A partial sequence of human insulinoma 67-kDa GAD was identical to human brain 67-kDa GAD. Allelic variations were observed in rat as well as in human 67-kDa GAD sequences. The expressed rat islet 67-kDa GAD protein is functional and is immunoprecipitated by IDDM sera; it comigrates electrophoretically with the 67-kDa islet autoantigen. The hydrophilic 67-kDa form of GAD in islets is an additional autoantigen in IDDM and is recognized by a different subset of autoantibodies than the 64-kDa autoantigen. Thus, mammalian cell lines expressing functionally active, recombinant GAD may become important tools to study the nature and the role of GAD autoreactivity in IDDM.
Michelsen
B K
BK
Hagedorn Research Laboratory, Gentofte, Denmark.
Petersen
J S
JS
Boel
E
E
Møldrup
A
A
Dyrberg
T
T
Madsen
O D
OD
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001324:Autoantigens / Q000235:genetics*; D003001:Cloning, Molecular; D003922:Diabetes Mellitus, Type 1 / Q000235:genetics / Q000276:immunology*; D005968:Glutamate Decarboxylase / Q000235:genetics*; D006801:Humans; D007340:Insulinoma / Q000235:genetics; D007515:Islets of Langerhans / Q000502:physiology; D008969:Molecular Sequence Data; D008970:Molecular Weight; D011233:Precipitin Tests; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D016415:Sequence Alignment; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D001324:Autoantigens; D012333:RNA, Messenger; D005680:gamma-Aminobutyric Acid; D005968:Glutamate Decarboxylase