Adult human pancreatic duct and islet cells exhibit similarities in expression and differences in phosphorylation and complex formation of the homeodomain protein Ipf-1

The homeodomain transcription factor encoded by the pancreatic and duodenal homeobox gene-1 (Ipf-1) is essential for pancreatic ontogenesis, Whether I pf-1 is also involved in the neogenesis of beta-cells in the adult pancreas is unknown. me examined whether Ipf-1 is expressed in adult human pancreat ic ducts, which are thought to generate new beta-cells. In tissue sections, virtually all duct cells mere immunopositive for Ipf-1, as were the islet beta-cells but not the acinar cells. After isolation and culture, both duct and islet cell preparations contained the Ipf-1 immunoreactive proteins p4 2 and p45 (42 and 45 kDa, respectively) in similar proportions, but the exp ression levels were twofold lower in duct cells. After 4 h of labeling, the endocrine cells exhibited a sevenfold higher phosphorylation of p42 than t he duct cells, whereas p45 was phosphorylated only in endocrine cells. Home obox binding transcription factor complexes with Ipf-1 in duct cells differ ed from those in endocrine cells in terms of gel mobility, sequence specifi city, and affinity. The observed similarities in Ipf-1 expression by adult human pancreatic duct cells and endocrine cells may reflect their common on togenic origin, whereas the differences in Ipf-1 phosphorylation and comple x formation may correlate with their divergent differentiation.