Characteristics of rat pancreatic regenerating protein.
BACKGROUND
The pancreatic regenerating (reg) gene is an acinar cell product involved in islet formation and maintenance. Human reg protein is mitogenic to pancreatic beta and ductular cells, and its amino acid sequence predicts it to be a calcium-dependent lectin.


METHODS
We studied the biologic activity and cellular localization of rat reg I isolated from the acinar cell line AR42J and the lectin properties of reg from AR42J and pancreatic juice. Bioactivity was assayed by mitogenesis on the ductular cell line ARIP. Cellular localization was determined by differential centrifugation. Lectin properties were assessed by affinity chromatography.


RESULTS
Reg protein from crude AR42J cellular lysate and purified reg protein from AR42J induced thymidine incorporation to ARIP. Conditioned medium from AR42J and co-culture of AR42J with morphologically distinguishable ARIP, however, failed to induce mitogenesis. Reg protein was localized within the vesicle fraction of the cell and was not membrane bound. Affinity chromatography revealed that reg protein did not bind to mannose or galactose in the presence or absence of calcium. In pancreatic juice a previously undescribed mannose-binding protein was discovered at 25,000 to 30,000 daltons.


CONCLUSIONS
We conclude that reg produced in the acinar cell line AR42J is biologically active but not efficiently secreted, even though it localized within the cellular vesicles. Despite predictions based on its amino acid sequence, it does not appear to be a calcium-dependent lectin.
Zenilman
M E
ME
Department of Surgery, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Chen
J
J
Danesh
B
B
Zheng
Q H
QH
D000818:Animals; D000906:Antibodies / Q000276:immunology; D015153:Blotting, Western; D002135:Calcium-Binding Proteins / Q000276:immunology / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D002460:Cell Line / Q000187:drug effects; D004591:Electrophoresis, Polyacrylamide Gel; D037102:Lectins / Q000378:metabolism; D051847:Lithostathine; D008934:Mitogens / Q000494:pharmacology; D009419:Nerve Tissue Proteins; D010179:Pancreas / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D010189:Pancreatic Juice / Q000378:metabolism; D051381:Rats; D014018:Tissue Distribution
D000906:Antibodies; D002135:Calcium-Binding Proteins; D037102:Lectins; D051847:Lithostathine; D008934:Mitogens; D009419:Nerve Tissue Proteins; C497616:Reg1a protein, rat