Gastroenterology

Gastroenterology

Volume 117, Issue 4, October 1999, Pages 823-830
Gastroenterology

Alimentary Tract
Identification of an autoimmune enteropathy–related 75-kilodalton antigen,☆☆,

https://doi.org/10.1016/S0016-5085(99)70340-9Get rights and content

Abstract

Background & Aims: We have previously reported a 75-kilodalton autoantigen specific to X-linked autoimmune enteropathy (AIE) associated with tubulonephropathy. The aim of this study was to identify the autoantigen. Methods: Complementary DNA (cDNA) clones were isolated by immunoscreening a human duodenal cDNA-expression library with serum from a patient with AIE. Results: cDNA encoding the 75-kilodalton antigen (AIE-75) was identified. The composite nucleotide sequence of the cDNA for AIE-75 was 2214 base pairs long and encoded 552 amino acids. The genomic sequence of AIE-75 was found in Sequence DataBank, which consisted of 21 exons and was located on the chromosome 11p14.3. Recombinant AIE-75 specifically reacted with sera from 3 of 4 unrelated patients with AIE but not with 58 control sera. AIE-75 was predominantly distributed in the epithelial cells of the luminal surface and the upper half of the crypts of the intestine and in the proximal renal tubulus. Similarity searches revealed that the AIE-75 cDNA sequence was an authentic form of several colon cancer–related cDNAs of unknown function. The deduced amino acid sequence contained 3 conserved PSD-95/Dlg/ZO-1 (PDZ) domains. Conclusions: AIE-75 is a PDZ domain–containing protein expressed in the differentiated epithelial cells of the intestine and kidney and may be involved in protein-protein interaction. The identification of the autoantigen may prove useful in the approach to the pathogenesis of this poorly understood disease.

GASTROENTEROLOGY 1999;117:823-830

Section snippets

Sera

AIE sera were obtained from 2 Japanese and 2 German patients. The clinical features of the Japanese patients with X-linked AIE associated with tubulonephropathy (AIE 1 and 2) have been reported previously.5, 11, 12 The German patients were men with definite AIE without apparent renal complications (AIE 3 and 4). Control sera were obtained from normal volunteers (n = 10) or from patients with bronchial asthma (n = 20), food allergy (n = 3), autoimmune diseases including systemic lupus

Isolation of cDNA encoding an antigen reactive with AIE serum

Approximately 106 clones of a λgt11 human duodenal cDNA expression library were screened with the serum from 1 of the patients with AIE. Four clones reactive with the AIE serum but not with any of the control sera were obtained. From these clones, the most immunoreactive clone (D6) containing a 1023–base pair (bp) cDNA was isolated in the first screening. The cDNA insert was used as a probe to rescreen the same library, and 3 overlapping clones were obtained. Of these clones, K2 was the largest

Discussion

We have previously described a 75-kilodalton autoantigen that reacted with sera from 2 patients with AIE associated with tubulonephropathy.11 In the present study, we identified the AIE-specific 75-kilodalton autoantigen by cloning the cDNA from a human duodenal cDNA library and named it AIE-75. The AIE-75 cDNA consisted of 21 exons encoding 552 amino acids, and its calculated molecular weight was 62,172. However, by producing protein from AIE-75 cDNA in reticulocyte lysate, we found that

Acknowledgements

The authors thank Dr. N. Kurauchi (First Department of Surgery, Hokkaido University School of Medicine) for providing the tissue samples and Drs. A. Yara (Department of Pediatrics, University of the Ryukyu), M. Konno and A. Imamura (Sapporo Kohsei Hospital), N. Ishikawa (Kitami Red Cross Hospital), and B. Lembcke (St. Barbara Hospital, Gladbeck, Germany) for providing sera. The authors also thank M. Yanome for help in preparing the manuscript.

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  • Cited by (0)

    Address requests for reprints to: Ichiro Kobayashi, M.D., Ph.D., Department of Pediatrics, Hokkaido University School of Medicine, North-15 West-7, Kita-ku, Sapporo 060-8638 Japan. e-mail: [email protected]; fax: 81-11-706-7898.

    ☆☆

    Supported in part by a Grant-in-Aid from the Ministry of Health and Welfare and a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan.

    The nucleotide sequence reported in this study has been submitted to the DNA Data Bank of Japan with accession numbers AB006955 and AB018687.

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