Journal Article

Dominant Negative Pathogenesis by Mutant Proinsulin in the Akita Diabetic Mouse

Shengli Zhao, Philippe A. Halban, Toshiyuki Takeuchi, Tetsuro Izumi, Hiromi Yokota-Hashimoto, Jie Wang

2003

Overview

Dominant Negative Pathogenesis by Mutant Proinsulin in the Akita Diabetic Mouse Tetsuro Izumi 1 , Hiromi Yokota-Hashimoto 1 , Shengli Zhao 1 , Jie Wang 1 , Philippe A. Halban 2 and Toshiyuki Takeuchi 1 1 Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, Maebashi, Japan 2 Louis-Jeantet Research Laboratories, University Medical Centre, Geneva, Switzerland Abstract Autosomal dominant diabetes in the Akita mouse is caused by mutation of the insulin 2 gene, whose product replaces a cysteine residue that is engaged in the formation of an intramolecular disulfide bond. These heterozygous mice exhibit severe insulin deficiency despite coexpression of normal insulin molecules derived from three other wild-type alleles of the insulin 1 and 2 genes. Although the results of our previous study suggested that the mutant proinsulin 2 is misfolded and blocked in the transport from the endoplasmic reticulum to the Golgi apparatus, its dominant negative nature has not been fully characterized. In the present study, we investigated the possible pathogenic mechanisms induced by the mutant proinsulin 2. There is no evidence that the mutant proinsulin 2 attenuates the overall protein synthesis rate or promotes the formation of aberrant disulfide bonds. The trafficking of constitutively secreted alkaline phosphatase, however, is significantly decreased in the islets of Akita mice, indicating that the function of early secretory pathways is nonspecifically impaired. Morphological analysis has revealed that secretory pathway organelle architecture is progressively devastated in the β-cells of Akita mice. These findings suggest that the organelle dysfunction resulting from the intracellular accumulation of misfolded proinsulin 2 is primarily responsible for the defect of coexisting wild-type insulin secretion in Akita β-cells. Footnotes Address correspondence and reprint requests to Dr. Tetsuro Izumi, Department of Molecular Medicine, Institute for Molecular and Cellular Regulation, Gunma University, 3-39-15 Showa-machi, Maebashi, Gunma 371-8512, Japan. E-mail: tizumi{at}showa.gunma-u.ac.jp . Received for publication 1 August 2002 and accepted in revised form 5 November 2002. Current address for J.W. is Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL 60637. ER, endoplasmic reticulum; SEAP, secretory alkaline phosphatase; TUNEL, transferase-mediated dUTP nick-end labeling. DIABETES

• Publisher: American Diabetes Association
• Subject: Amino Acid Substitution / Animals / Base Sequence / Biological and medical sciences / Cell death / Chemical bonds / CHO Cells / Cloning / Cricetinae / Cysteine / Cysteine Endopeptidases - metabolism / Diabetes / Diabetes Mellitus, Type 1 - genetics / Diabetes Mellitus, Type 1 - pathology / Diabetes. Impaired glucose tolerance / DNA Primers / Endocrine pancreas. Apud cells (diseases) / Endocrinopathies / Endoplasmic reticulum / Endoplasmic Reticulum - metabolism / Etiopathogenesis. Screening. Investigations. Target tissue resistance / Genes / Genes, Dominant / Genetic aspects / Genetic disorders / Genotype & phenotype / Golgi Apparatus - metabolism / Heterozygote / Insulin / Islands of Langerhans / Islets of Langerhans / Islets of Langerhans - pathology / Islets of Langerhans - physiology / Islets of Langerhans - ultrastructure / Medical sciences / Mice / Mice, Mutant Strains / Multienzyme Complexes - metabolism / Mutagenesis, Site-Directed / Mutation / Pathogenesis / Phosphatase / Physiological aspects / Proinsulin / Proinsulin - genetics / Proinsulin - metabolism / Protease Inhibitors - pharmacology / Proteasome Endopeptidase Complex / Protein Denaturation / Protein Folding / Protein Transport / Proteins / Recombinant Proteins - metabolism / Transfection