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FRIMEDBIO-Fri prosj.st. med.,helse,biol

Proteotoxicity in Chronic Pancreatitis and Diabetes

Alternative title: Giftige proteiner i bukspyttkjertelbetennelse og diabetes

Awarded: NOK 9.9 mill.

Project Manager:

Project Number:

289534

Application Type:

Project Period:

2019 - 2023

Subject Fields:

Partner countries:

Serious neurological disorders like Parkinson’s and Alzheimer’s disease are characterized by proteins forming aggregates in the brain tissue. The aim of our project was to investigate whether aggregating proteins with toxic effects play a role also in pathologic processes of the pancreas. We have studied the digestive enzyme carboxyl-ester lipase (CEL), which we several years ago discovered to be involved in the development of some forms of diabetes and pancreatitis. The pathogenic CEL variants are caused by mutations that disrupt the tail region of the enzyme, triggering protein aggregation and stress reactions within the cells. Our hypothesis has been that abnormal CEL molecules initiate a degenerative disease process in the pancreas. In the project, we employed a diversity of molecular and cellular methods to analyze genetic variants of CEL found in patients with diabetes and/or pancreatitis. The project has enabled us to discover new variants of the CEL gene and determine if these are benign or pathogenic. In the project period, we have identified several new families with CEL mutations and published a paper describing how to diagnose such patients. Some of these CEL variants form aggregates both inside and outside of cells, and we have in the project investigated whether aggregated CEL molecules can spread directly from cell to cell. In particular, we have demonstrated that they can be taken up by the insulin-producing cells of the pancreas and that such uptake negatively impacts normal cellular function. Pathogenic processes in humans can often be recapitulated by expressing the disrupted protein in animals. In the project, we have therefore created two different mouse models where a part of the rodent CEL protein is replaced by the pathogenic part of the human CEL protein. These mice exhibit clear signs of chronic pancreatitis. The effect is very similar to that observed in humans carrying the pathogenic CEL variants. Data from one of the mouse models have been published, while the other model will be published after the project is finished. In summary, our studies indicate that aggregation of a digestive enzyme represents a novel mechanism that induces pancreatic disease. We now know more about which CEL variants are benign and which variants are pathogenic. The project has therefore delivered knowledge directly applicable for patient diagnostics.

(1) Basert på mutasjonar som naturleg førekjem i pasientar, har vi laga to nye musemodellar for inflammasjon i bukspyttkjertelen. Ved å studere desse dyremodellane er det oppnådd ny kunnskap om korleis sjukdom som diabetes og kronisk pankreatitt kan oppstå. (2) Vi har funne nye familiar med diabetes og pankreatitt forårsaka av mutasjonar i genet CEL. Vi har no ei betre forståing av kva for CEL-variantar som gir sjukdom og kva for variantar som kroppen kan tolerere. (3) Gjennom den internasjonale delen av prosjektet har vi utvikla og forsterka forskingssamarbeidet med to verdsleiande miljø i USA (Washington School of Medicine, St. Louis og Joslin Diabetes Center, Harvard Medical School, Boston). Desse samarbeida vil vere av stor verdi for vår vidare forsking på mekanismar bak sjukdom i bukspyttkjertelen.

Formation of protein aggregates is a fundamental characteristic of many degenerative disorders. We have discovered that aberrant variants of the digestive enzyme carboxyl-ester lipase (CEL) are involved in the development of chronic pancreatitis and diabetes. The pathogenic molecules are generated by mutations that change the repetitive tail region of CEL. We have found that these CEL variants cause the protein to misfold, triggering endoplasmic reticulum (ER) stress and the unfolded protein response. When such processes do not restore protein balance in the ER, cellular function becomes severely impaired, defining the misfolded molecules as proteotoxic. Our overriding hypothesis is that proteotoxic lipase molecules can initiate a degenerative disease process in the pancreas. Hence, we will systematically analyze CEL mutations discovered in patients by employing a diversity of molecular and cellular methods. Based on our observation of extracellular CEL aggregates, we will also investigate whether misfolded CEL molecules can spread directly from cell to cell and be taken up by pancreatic endocrine cells, negatively impacting their function. Moreover, we propose that pancreatic degenerative disease can be recapitulated in animals by organ-specific expression of pathogenic human CEL variants. We will therefore construct humanized knock-in mice models where the tail of the mouse Cel protein is replaced by either the normal tail or two pathogenic repetitive tail sequences from the human CEL protein. These mice will be exposed to environmental stressors known to induce pancreatitis and diabetes. Completion of our studies will establish mutation-induced misfolding of digestive enzymes as a relevant disease mechanism in the pathogenesis of chronic pancreatitis and diabetes. The project will also yield general knowledge about how changes in a repetitive protein domain cause human degenerative disease, thereby defining key initial events in protein aggregation disorders.

Funding scheme:

FRIMEDBIO-Fri prosj.st. med.,helse,biol

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