title: Diabetes and pancreatic exocrine dysfunction due to mutations in the carboxyl ester lipase gene-maturity onset diabetes of the young (CEL-MODY): a protein misfolding disease.
abstract: CEL-maturity onset diabetes of the young (MODY), diabetes with pancreatic lipomatosis and exocrine dysfunction, is due to dominant frameshift mutations in the acinar cell carboxyl ester lipase gene (CEL). As Cel knock-out mice do not express the phenotype and the mutant protein has an altered and intrinsically disordered tandem repeat domain, we hypothesized that the disease mechanism might involve a negative effect of the mutant protein. In silico analysis showed that the pI of the tandem repeat was markedly increased from pH 3.3 in wild-type (WT) to 11.8 in mutant (MUT) human CEL. By stably overexpressing CEL-WT and CEL-MUT in HEK293 cells, we found similar glycosylation, ubiquitination, constitutive secretion, and quality control of the two proteins. The CEL-MUT protein demonstrated, however, a high propensity to form aggregates found intracellularly and extracellularly. Different physicochemical properties of the intrinsically disordered tandem repeat domains of WT and MUT proteins may contribute to different short and long range interactions with the globular core domain and other macromolecules, including cell membranes. Thus, we propose that CEL-MODY is a protein misfolding disease caused by a negative gain-of-function effect of the mutant proteins in pancreatic tissues.
authors.affiliation: Department of Clinical Medicine, University of Bergen, N-5020 Bergen, Norway.
authors.forename: Bente B
authors.initials: BB
authors.lastname: Johansson
authors.forename: Janniche
authors.initials: J
authors.lastname: Torsvik
authors.forename: Lise
authors.initials: L
authors.lastname: Bjørkhaug
authors.forename: Mette
authors.initials: M
authors.lastname: Vesterhus
authors.forename: Anja
authors.initials: A
authors.lastname: Ragvin
authors.forename: Erling
authors.initials: E
authors.lastname: Tjora
authors.forename: Karianne
authors.initials: K
authors.lastname: Fjeld
authors.forename: Dag
authors.initials: D
authors.lastname: Hoem
authors.forename: Stefan
authors.initials: S
authors.lastname: Johansson
authors.forename: Helge
authors.initials: H
authors.lastname: Ræder
authors.forename: Susanne
authors.initials: S
authors.lastname: Lindquist
authors.forename: Olle
authors.initials: O
authors.lastname: Hernell
authors.forename: Miriam
authors.initials: M
authors.lastname: Cnop
authors.forename: Jaakko
authors.initials: J
authors.lastname: Saraste
authors.forename: Torgeir
authors.initials: T
authors.lastname: Flatmark
authors.forename: Anders
authors.initials: A
authors.lastname: Molven
authors.forename: Pål R
authors.initials: PR
authors.lastname: Njølstad
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D043182:Carboxylesterase / Q000235:genetics*; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009154:Mutation; D046790:Pancreas, Exocrine / Q000378:metabolism* / Q000503:physiopathology; D011107:Polylysine / Q000737:chemistry; D011485:Protein Binding; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid
chemical_list: D011107:Polylysine; D043182:Carboxylesterase