Human Prohormone Convertase 3 Gene: Exon-Intron Organization and Molecular Scanning for Mutations in Japanese Subjects With NIDDM

Abstract

Proinsulin is converted to insulin by the concerted action of two sequence-specific subtilisin-like proteases termed prohormone convertase 2 (PC2) and prohormone convertase 3 (PC3). PC3 is a type I proinsulin-processing enzyme that initiates the sequential processing of proinsulin to insulin by cleaving the proinsulin molecule on the COOH-terminal side of the dibasic peptide, Arg31-Arg32, joining the B-chain and C-peptide. Thus, PC3 plays a key role in regulating insulin biosynthesis. Expressions of insulin and PC3, but not PC2, are coordinately regulated by glucose, consistent with the important role of PC3 in regulating proinsulin processing. NIDDM is associated with increased secretion of proinsulin and proinsulin-like molecules, suggesting that mutations in the PC3 gene may be involved in the development of this disorder. To examine this hypothesis, we have isolated and characterized the human PC3 gene and screened it for mutations in a group of Japanese subjects with NIDDM. The PC3 gene consists of 14 exons spanning more than 35 kb. The exon-intron organization of PC2 and PC3 genes are conserved, consistent with a common evolutionary origin for the prohormone convertase gene family. Single-strand conformational analysis and nucleotide sequencing of the entire coding region of the PC3 gene in 102 Japanese subjects with NIDDM revealed missense mutations in exons 2 (Arg/Gln53) and 14 (Gln/Glu638), neither of which was associated with NIDDM in this population. These data suggest that genetic variation in the PC3 gene is unlikely to be a major contributor to NIDDM susceptibility in Japanese.

Expression of PC3, carboxypeptidase E and enkephalin in human monocyte‐derived macrophages as a tool for genetic studies

“…The obesity and hyperglycaemia observed in the fat/fat mouse are a consequence of a mutation in the CPE gene [6]. A deficiency in PC3 activity has been proposed to be the causitive agent responsible for a unique form of hyperproinsulinemia in a human subject [7], and may also be related to the elevated proinsulin levels associated with Type 2 diabetes [8]. The reported presence of PC2 in rat polymorphonuclear leukocytes and alveolar macrophages and PC3 in rat "Corresponding author.…”

Adenoviral vector-mediated insulin gene transfer in the mouse pancreas corrects streptozotocin-induced hyperglycemia

“…[8][9][10] Processing of proinsulin to mature insulin requires two prohormone convertases relatively specific to the ␤-cell. [11][12][13][14][15][16][17] Several studies have shown that it is possible to process proinsulin to its mature form in non-␤-cells by engineering furin cleavage sites in the proinsulin mol- ecule. [18][19][20][21][22][23][24][25][26][27][28] When 293 cells are transfected with a human furin modified proinsulin cDNA, efficient processing and constitutive secretion of biologically active insulin was documented.…”

Gene organization and alternative splicing of human prohormone convertase PC8

“…Previous reports of the structural organization of the genes of mammalian prohormone convertases have demonstrated a high degree of conservation in the gene organization of this enzyme family [6,[29][30][31][32][33]. A comparison of intron-exon splice junctions of hPC8 with those of hPC1, hPC2, hPACE, mouse (m)PC4 and human furin genes illustrated a distinctive divergence of the gene organization of human PC8 from the striking conservation of splice boundaries observed in the gene organizations of other convertase family members.…”