title: Impaired NH2-terminal processing of human proislet amyloid polypeptide by the prohormone convertase PC2 leads to amyloid formation and cell death.
abstract: Islet amyloid, formed by aggregation of islet amyloid polypeptide (IAPP; amylin), is a pathological characteristic of the pancreas in type 2 diabetes and may contribute to the progressive loss of beta-cells in this disease. We tested the hypothesis that impaired processing of the IAPP precursor proIAPP contributes to amyloid formation and cell death. GH3 cells lacking the prohormone convertase 1/3 (PC1/3) and IAPP and with very low levels of prohormone convertase 2 (PC2) were transduced with adenovirus (Ad) expressing human or rat (control) proIAPP linked to green fluorescent protein, with or without Ad-PC2 or Ad-PC1/3. Expression of human proIAPP increased the number of transferase-mediated dUTP nick-end labeling (TUNEL)-positive cells 96 h after transduction (+hIAPP 8.7 +/- 0.4% vs. control 3.0 +/- 0.4%; P < 0.05). COOH-terminal processing of human proIAPP by PC1/3 increased (hIAPP+PC1/3 10.4 +/- 0.7%; P < 0.05), whereas NH(2)-terminal processing of proIAPP by addition of PC2 markedly decreased (hIAPP+PC2 5.5 +/- 0.5%; P < 0.05) the number of apoptotic GH3 cells. Islets from mice lacking PC2 and with beta-cell expression of human proIAPP (hIAPP(+/+)/PC2(-/-)) developed amyloid associated with beta-cell death during 2-week culture. Rescue of PC2 expression by ex vivo transduction with Ad-PC2 restored NH(2)-terminal processing to mature IAPP and decreased both the extent of amyloid formation and the number of TUNEL-positive cells (-PC2 26.5 +/- 4.1% vs. +PC2 16.1 +/- 4.3%; P < 0.05). These findings suggest that impaired NH(2)-terminal processing of proIAPP leads to amyloid formation and cell death and that accumulation of the NH(2)-terminally extended human proIAPP intermediate may be a critical initiating step in amyloid formation.
authors.affiliation: Deparment of Pathology and Laboratory Medicine and Child and Family Research Institute, University of British Columbia, Vancouver, BC, Canada. marzban@interchange.ubc.ca
authors.forename: Lucy
authors.initials: L
authors.lastname: Marzban
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Rhodes
authors.forename: Donald F
authors.initials: DF
authors.lastname: Steiner
authors.forename: Leena
authors.initials: L
authors.lastname: Haataja
authors.forename: Philippe A
authors.initials: PA
authors.lastname: Halban
authors.forename: C Bruce
authors.initials: CB
authors.lastname: Verchere
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000682:Amyloid / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D015870:Gene Expression; D049452:Green Fluorescent Proteins / Q000235:genetics; D006801:Humans; D020287:In Situ Nick-End Labeling; D007515:Islets of Langerhans / Q000201:enzymology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010446:Peptide Fragments / Q000378:metabolism; D010903:Pituitary Gland, Anterior; D045706:Proprotein Convertase 2 / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D011993:Recombinant Fusion Proteins; D014162:Transfection
chemical_list: D000682:Amyloid; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; C485184:enhanced green fluorescent protein; C422904:pro-islet amyloid polypeptide; D049452:Green Fluorescent Proteins; D045706:Proprotein Convertase 2