Pancreatic islet β-cells secrete the hormones insulin, amylin and pancreastatin. To search for further β-cell hormones, we purified peptides from secretory granules isolated from cultured murine βTC6-F7 β-cells. We identified a 34-amino-acid peptide (3948Da), corresponding to Asp69–Leu102 of the proinsulin-like growth factor II E-peptide, which we have termed ‘preptin’. Preptin, is present in islet β-cells and undergoes glucose-mediated co-secretion with insulin. Synthetic preptin increases insulin secretion from glucose-stimulated βTC6-F7 cells in a concentration-dependent and saturable manner. Preptin infusion into the isolated, perfused rat pancreas increases the second phase of glucose-mediated insulin secretion by 30%, while anti-preptin immunoglobulin infusion decreases the first and second phases of insulin secretion by 29 and 26% respectively. These findings suggest that preptin is a physiological amplifier of glucose-mediated insulin secretion.
- β-cell granules
- perfused pancreas
- proIGF-II E-peptide
- protein mass spectrometry
- secretory granules
Abbreviations used: FBS, fetal bovine serum; HBSS, Hanks balanced salt solution; KRB, Krebs–Ringer buffer; MALDI–TOF-MS, matrix-assisted laser-desorption ionization–time-of-flight MS; PLIM, preptin-like immunoreactive material; proIGF-II, proinsulin-like growth factor II; RP-HPLC, reversed-phase HPLC; TFA, trifluoroacetic acid.
- The Biochemical Society, London ©2001