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.
Hagedorn Research Laboratory, Gentofte, Denmark.
B K
BK
Michelsen
J S
JS
Petersen
E
E
Boel
A
A
Møldrup
T
T
Dyrberg
O D
OD
Madsen
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