Establishment of an enzyme-linked immunosorbent assay for mouse pancreatic polypeptide clarifies the regulatory mechanism of its secretion from pancreatic γ cells

Abstract

Pancreatic polypeptide (PP), secreted from γ cells of the islets of Langerhans, is a 36 amino-acid peptide encoded by the Ppy gene. Although previous studies have reported that PP causes a decrease in appetite, the molecular mechanism that regulates PP secretion has not been fully elucidated. Lack of understanding of the regulatory mechanism of PP secretion may be partially owing to the lack of assay systems that can specifically detect PP. We recently developed the mouse monoclonal antibody 23-2D3 that specifically recognizes PP. In the present study, we developed a sandwich enzyme-linked immunosorbent assay for the measurement of mouse PP, and directly monitored intracellular Ca2+ concentrations in Ppy-expressing cells from a newly developed reporter mouse. Using these systems, we identified agonists, such as carbachol and glucose-dependent insulinotropic polypeptide (GIP), which stimulate PP secretion. We further demonstrated that, unlike the case of GIP-induced insulin secretion from β cells, there is a unique mechanism by which PP secretion is triggered by an increase in intracellular Ca2+ concentrations via voltage-dependent calcium channels even in low-glucose conditions.

Identification of Ppy‐lineage cells as a novel origin of pancreatic ductal adenocarcinoma

“…Pancreata were exposed, and 25 U/ml collagenase (type XI; Sigma-Aldrich, St Louis, MO, USA) was injected. Thereafter, the islets were isolated from acinar tissue as described previously [26,27]. The PDAC cell line isolated from the pancreatic tumour of an LSL-Kras G12D/+ ;LSL-Trp53 flox/+ ;Ptf1a Cre/+ (KPC) mouse [28] was used as a positive control.…”

Pancreatic polypeptide revisited: Potential therapeutic effects in obesity-diabetes

“…In addition, GIP has also been demonstrated to stimulate PP secretion [98], but the implication of this is not yet confirmed. Although, the GIP stimulatory effect, that appears to be dependent on calcium channel activity, has recently been confirmed following development of a new sandwich enzyme-linked immunosorbent assay for assessing mouse islet PP secretion [82]. Interestingly, there is a suggested link between glucagon and PP secretion [4], with GIP also known to directly modulate glucagon secretion [19], that could represent an as yet unexplored link between the complementary islet effects of PP and GIP.…”