LOCALIZATION OF PEPTIDE TRANSPORTER IN NUCLEI AND LYSOSOMES OF THE PANCREAS

Conclusions. These studies show for the first time the localization of a H+/peptide cotransporter in nuclei of vascular smooth muscle cells and Schwann cells and its localization in lysosomes of the exocrine pa ncreas. It is likely that the transporter functions to move small pept ides from the lysosome to the cytoplasm following intralysosomal prote in degradation. The nature of the transporter function in the nucleus remains to be determined, including the possibility that peptide signa ling molecules may be transmitted between nucleus and cytoplasm, Backg round. PEPT1 transports di-and tripeptides through plasma membranes. P eptides are cotransported with H+, thus deriving the energy for the ac tive transport process from an electrochemical H+ gradient. The main r egions in which PEPT1 has been thought to function are the plasma memb ranes of the small intestinal epithelial cells for absorption of prote in digestion products and in the kidney tubules for recovery of small peptides from the glomerular filtrate. Methods. Pancreas was removed f rom rats and quick frozen with liquid nitrogen. Frozen sections were f ixed in cold acetone. Sections were incubated with primary antibody ag ainst PEPT1, followed by a secondary antibody conjugated with fluoresc ein, then examined with a fluorescence microscope. Results, Three majo r structures were immunopositive with the antibody to PEPT1: the nucle i of smooth muscle cells in the wall of arterioles, the nuclei of Schw ann cells in unmyelinated pancreatic nerves, and lysosomes in acinar c ells.