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- Title
Revisiting Proinsulin Processing: Evidence That Human β-Cells Process Proinsulin With Prohormone Convertase (PC) 1/3 but Not PC2.
- Authors
Ramzy, Adam; Asadi, Ali; Kieffer, Timothy J.
- Abstract
Insulin is first produced in pancreatic β-cells as the precursor prohormone proinsulin. Defective proinsulin processing has been implicated in the pathogenesis of both type 1 and type 2 diabetes. Though there is substantial evidence that mouse β-cells process proinsulin using prohormone convertase 1/3 (PC1/3) and then prohormone convertase 2 (PC2), this finding has not been verified in human β-cells. Immunofluorescence with validated antibodies revealed that there was no detectable PC2 immunoreactivity in human β-cells and little PCSK2 mRNA by in situ hybridization. Similarly, rat β-cells were not immunoreactive for PC2. In all histological experiments, PC2 immunoreactivity in neighboring α-cells acted as a positive control. In donors with type 2 diabetes, β-cells had elevated PC2 immunoreactivity, suggesting that aberrant PC2 expression may contribute to impaired proinsulin processing in β-cells of patients with diabetes. To support histological findings using a biochemical approach, human islets were used for pulse-chase experiments. Despite inhibition of PC2 function by temperature blockade, brefeldin A, chloroquine, and multiple inhibitors that blocked production of mature glucagon from proglucagon, β-cells retained the ability to produce mature insulin. Conversely, suppression of PC1/3 blocked processing of proinsulin but not proglucagon. By demonstrating that healthy human β-cells process proinsulin by PC1/3 but not PC2, we suggest that there is a need to revise the long-standing theory of proinsulin processing.
- Subjects
PROINSULIN; TYPE 1 diabetes; TYPE 2 diabetes; IN situ hybridization; ANIMAL experimentation; COMPARATIVE studies; IMMUNOHISTOCHEMISTRY; ISLANDS of Langerhans; RESEARCH methodology; MEDICAL cooperation; MICE; PROTEOLYTIC enzymes; RESEARCH; EVALUATION research
- Publication
Diabetes, 2020, Vol 69, Issue 7, p1451
- ISSN
0012-1797
- Publication type
journal article
- DOI
10.2337/db19-0276