Thesis (doctoral)--Ludwig Maximilians-Universität zu München, 1979.

Die transkriptionelle Aktivierung des HDC Gens sowie des Chromogranin A Gens in ECL-Zellen der Magenmucosa repräsentiert einen zentralen Mechanismus der Säureregulation durch Gastrin und scheint ausserdem Bedeutung für die Pathogenese der gastroduodenalen Ulkuskrankheit zu haben. Unsere Untersuchungen identifizieren erstmals die molekularen Mechanismen der Gastrin-abhängigen Regulation beider Gene und definieren die beteiligten Transkriptionsfaktoren, regulatorischen DNA-Elemente und intrazellulären Signalwege. Des weiteren wurde durch transgene Untersuchungen die transkriptionelle Regulation des ChromograninA Gens in vivo bestätigt und die neuroendokrin-spezifische Expression eines 4.8kB-langen CgA-Promotorfragmentes demonstriert. Als pathobiologisch relevante Aktivatoren des HDC Gens konnten oxidativer Stress sowie die H. pylori Infektion identifiziert und hinsichtlich ihrer molekularen Wirkungen auf das Schlüsselgen der Histaminsynthese im Magen charakterisiert werden. Diese Ergebnisse dokumentieren einen potentiellen Mechanismus für die Interaktion beider Stimuli mit den physiologischen Regelkreisen der Magensäureregulation und können durch die Definition neuer molekularer Angriffspunkte möglicherweise zur Entwicklung innovativer Therapieansätze beitragen. / Transcriptional activation of the genes encoding histidine decarboxylase and chromogranin A represents a key mechanism of gastrin-dependent acid regulation and also appears to be involved in the pathogenesis of gastroduodenal ulcer disease. Our results for the first time identify the molecular mechanisms underlying gastrin-dependent activation of both genes, and define the transcription factors, regulatory DNA elements and signal transduction pathways involved in this process. Furthermore, transgenic studies confirmed the principle of gastrin-dependent transcriptional activation of the chromogranin A gene in vivo, and demonstrated neuroendocrine-specific expression of a 4.8kB-CgA promotor fragment. In addition, the pathobiological stimuli oxidative stress and H. pylori were molecularly characterized regarding their activating effects on the key gene of gastric histamine sythesis. These results provide potential mechanisms for the interaction of both stimuli with regulatory circuits of gastric acid secretion, and can probably contribute via definition of new molecular targets to the development of inovative therapeutic strategies.

Systemic lupus erythematosus (SLE) is the prototypic systemic autoimmune disease, whereas autoimmune polyendocrine syndrome type 1 (APS1) is a rare autosomal disorder characterized by combinations of organ-specific autoimmune manifestations including hypoparathyroidism and intestinal dysfunction, and may serve as a model for organ-specific autoimmunity. Autoantibodies directed against proteins expressed in the affected tissues are found in both diseases. From a chondrocyte cDNA expression library, we identified the protein AHNAK as an autoantigen in SLE. Anti-AHNAK antibodies were found in 29.5% (18/61) of patients with SLE, 4.6% (5/109) of patients with rheumatoid arthritis, and 1.2% (2/172) of blood donors. Using a candidate approach, we analyzed the prevalence in APS1 and other organ-specific autoimmune diseases, of autoantibodies against the pyridoxal phosphate-dependent enzymes histidine decarboxylase (HDC) and cysteine sulfinic acid decarboxylase (CSAD), which are structurally closely related to known autoantigens. Anti-HDC and anti-CSAD reactivity was detected exclusively in APS1 patient sera. Anti-HDC antibodies were detected in 37.1% (36/97) of the APS1 sera, did not cross-react with aromatic L-amino acid decarboxylase, and were associated with intestinal dysfunction and loss of histamine-producing gastric enterochromaffin-like cells. In contrast, anti-CSAD reactivity was detected in 3.6% (3/83) of APS1 sera and cross-reacted with recombinant glutamic acid decarboxylase. From a parathyroid cDNA expression library, novel spliced transcripts of the CLLD4 gene on human chromosome 13q14, encoding 26 and 31 kDa isoforms recognized by autoantibodies in 3.4% (3/87) of APS1 patients, were identified and found to be preferentially expressed in lung and ovary. Both isoforms contain an N-terminal BTB/POZ domain, similarly to the TNF-alpha-regulated protein B12, localize both to the cytoplasm and nucleus in transfected COS cells, and form oligomers in vitro. The CLLD4 gene is located in a region frequently deleted in several forms of cancer, including lung and ovarian tumors. In conclusion, we have identified and partially characterized AHNAK and HDC as two common targets of autoantibodies in SLE and APS1, respectively. We have also identified CSAD and CLLD4 as two minor autoantigens in APS1, one of which is a novel protein with unknown function.