Endocytosis of Secreted Carboxyl-ester Lipase in a Syndrome of Diabetes and Pancreatic Exocrine Dysfunction [Protein Synthesis and Degradation]

August 25th, 2014 by Torsvik, J., Johansson, B. B., Dalva, M., Marie, M., Fjeld, K., Johansson, S., Bjorkoy, G., Saraste, J., Njolstad, P. R., Molven, A.

Maturity-onset diabetes of the young, type 8 (MODY8) is characterized by a syndrome of autosomal dominantly inherited diabetes and exocrine pancreatic dysfunction. It is caused by deletion mutations in the last exon of the carboxyl-ester lipase ( CEL ) gene, resulting in a CEL protein with increased tendency to aggregate. In this study, we have investigated the intracellular distribution of the wild type (WT) and mutant (MUT) CEL proteins in cellular models. We found that both CEL-WT and CEL-MUT were secreted via the ER and Golgi compartments. However, their subcellular distributions differed as only CEL-MUT was observed as aggregates at the cell surface and inside large cytoplasmic vacuoles. Many of the vacuoles were identified as components of the endosomal system and after its secretion, the mutant CEL protein was re-internalized, transported to the lysosomes and degraded. Internalization of CEL-MUT also led to reduced viability of pancreatic acinar and beta cells. These findings may have implications for the understanding of how the acinar-specific CEL-MUT protein causes both exocrine and endocrine pancreatic disease.
  • Posted in Journal of Biological Chemistry, Publications
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