Altered cellular localisation and expression, together with unconventional protein trafficking, of prion protein, PrPC, in type 1 diabetes

• Published in: Diabetologia 2021-10, Vol.64 (10), p.2279-2291
• Main Authors: Hiller, Helmut, Yang, Changjun, Beachy, Dawn E., Kusmartseva, Irina, Candelario-Jalil, Eduardo, Posgai, Amanda L., Nick, Harry S., Schatz, Desmond, Atkinson, Mark A., Wasserfall, Clive H.
• Format: Article
• Language: English
• Subjects: Autoantibodies; Beta cells; Cell adhesion molecules; Diabetes; Diabetes mellitus (insulin dependent); Endoplasmic reticulum; Gene expression; Human Physiology; Immunofluorescence; Insulin; Internal Medicine; Localization; Medicine; Medicine & Public Health; Metabolic Diseases; Morphogenesis; Neural cell adhesion molecule; Organ donors; Pancreas; Prion protein; Protein transport; Proteins; Scrapie
• ISSN: 0012-186X; 1432-0428
• DOI: 10.1007/s00125-021-05501-8

Aims/hypothesis Normal cellular prion protein (PrP C ) is a conserved mammalian glycoprotein found on the outer plasma membrane leaflet through a glycophosphatidylinositol anchor. Although PrP C is expressed by a wide range of tissues throughout the body, the complete repertoire of its functions has not been fully determined. The misfolded pathogenic isoform PrP Sc (the scrapie form of PrP) is a causative agent of neurodegenerative prion diseases. The aim of this study is to evaluate PrP C localisation, expression and trafficking in pancreases from organ donors with and without type 1 diabetes and to infer PrP C function through studies on interacting protein partners. Methods In order to evaluate localisation and trafficking of PrP C in the human pancreas, 12 non-diabetic, 12 type 1 diabetic and 12 autoantibody-positive organ donor tissue samples were analysed using immunofluorescence analysis. Furthermore, total RNA was isolated from 29 non-diabetic, 29 type 1 diabetic and 24 autoantibody-positive donors to estimate PrP C expression in the human pancreas. Additionally, we performed PrP C -specific immunoblot analysis on total pancreatic protein from non-diabetic and type 1 diabetic organ donors to test whether changes in PrP C mRNA levels leads to a concomitant increase in PrP C protein levels in human pancreases. Results In non-diabetic and type 1 diabetic pancreases (the latter displaying both insulin-positive [INS(+)] and -negative [INS(−)] islets), we found PrP C in islets co-registering with beta cells in all INS(+) islets and, strikingly, unexpected activation of PrP C in alpha cells within diabetic INS(−) islets. We found PrP C localised to the plasma membrane and endoplasmic reticulum (ER) but not the Golgi, defining two cellular pools and an unconventional protein trafficking mechanism bypassing the Golgi. We demonstrate PrP C co-registration with established protein partners, neural cell adhesion molecule 1 (NCAM1) and stress-inducible phosphoprotein 1 (STI1; encoded by STIP1 ) on the plasma membrane and ER, respectively, linking PrP C function with cyto-protection, signalling, differentiation and morphogenesis. We demonstrate that both PRNP (encoding PrP C ) and STIP1 gene expression are dramatically altered in type 1 diabetic and autoantibody-positive pancreases. Conclusions/interpretation As the first study to address PrP C expression in non-diabetic and type 1 diabetic human pancreas, we provide new insights for PrP C in the pathogenesis of