Human pancreatitis-associated protein. Messenger RNA cloning and expression in pancreatic diseases.

A human pancreatic cDNA library was screened with the cDNA encoding rat "pancreatitis-associated protein" (PAP). The selected clone encoded a secretory protein structurally related to rat PAP. The protein had the same size as rat PAP and showed 71% amino acid identity, the six half-cystines being in identical positions. Domains of the proteins showing homologies with calcium-dependent lectins were also conserved. In addition, expression in pancreas of the genes encoding the human protein and rat PAP showed similar characteristics: both were expressed at very low levels in control tissue and overexpressed during the acute phase of pancreatitis, contrary to most secretory products. The human protein was therefore named human pancreatitis-associated protein (PAP-H). Antibodies raised to a synthetic peptide of PAP-H detected a single band with an M(r) compatible with PAP-H in Western blot analysis of proteins extracted from a pancreas presenting with acute pancreatitis. In that tissue, the protein could be immunolocalized to the apical regions of acinar cells. An immunoassay was also constructed to quantify the protein in serum. Elevated PAP-H levels were observed in patients with acute pancreatitis and in some patients with chronic pancreatitis. Values were close to background in healthy subjects and in patients with other abdominal diseases. These results confirm that PAP-H synthesis increases during inflammation and suggest a possible use of the protein as biological marker of acute pancreatitis.

In vitro studies of the thyroglobulin degradation pathway: endocytosis and delivery of thyroglobulin to lysosomes, release of thyroglobulin cleavage products--iodotyrosines and iodothyronines.

UNLABELLED: Iodinated thyroglobulin stored in the thyroid follicular lumen is subjected to an internalization process and thought to be transferred into the lysosomal compartment for proteolytic cleavage and thyroid hormone release. In the present study, we have designed in vitro models to study: 1) the transfer of endocytosed thyroglobulin into lysosomes, and 2) the intracellular fate of free thyroid hormones and iodinated precursors generated by intralysosomal proteolysis of thyroglobulin. Open follicles prepared from pig thyroid tissue by collagenase treatment were used to probe the delivery of exogenous thyroglobulin to lysosomes via the differentiated apical cell membrane. Open follicles were incubated with pure [125I]thyroglobulin with or without unlabeled thyroglobulin in the presence or in the absence of chloroquine. Subcellular fractionation on a Percoll gradient showed that [125I]thyroglobulin was internalized and present in low (for the major part) and high density thyroid vesicles. In chloroquine-treated open follicles, we observed the appearance of a definite fraction of [125I]thyroglobulin in a lysosome subpopulation having the expected properties of phagolysosomes or secondary lysosomes. In contrast, in control open follicles, the amount of [125I]thyroglobulin or degradation products found in high density vesicles was lower and associated with the bulk of lysosomes, i.e., primary lysosomes. The content in thyroglobulin and degradation products of lysosomes at steady-state was analyzed by Western blot using polyclonal anti-pig thyroglobulin antibodies. Under reducing conditions, immunoreactive thyroglobulin species correspond to polypeptides with molecular weights ranging from 130,000 to less than 20,000. The presence of free thyroid hormones and iodotyrosines inside lysosomes and their intracellular fate was studied in dispersed thyroid cells labeled with [125I]iodide. Neo-iodinated [125I]thyroglobulin gave rise to free [125I]T4 which was secreted into the medium. In addition to released [125I]T4, a fraction of free [125I]T4 was identified inside the cells. Lysosomes isolated from dispersed thyroid cells did not contain significant amounts of free [125I]T4. The free intracellular [125I]T4 fraction seems to represent an intermediate 'hormonal pool' between thyroglobulin-bound T4 and secreted T4. Evidence for such a precursor-product relationship was obtained from pulse-chase experiments. IN CONCLUSION: 1) open thyroid follicles have the ability to internalize thyroglobulin by a mechanism of limited capacity and to address the endocytosed ligand to lysosomes.(ABSTRACT TRUNCATED AT 400 WORDS)

Messenger RNA sequence and expression of rat pancreatitis-associated protein, a lectin-related protein overexpressed during acute experimental pancreatitis.

Rat pancreatitis-associated protein (PAP) is an additional protein appearing in pancreatic juice after induction of prancreatic inflammation. Its messenger RNA was cloned and sequenced from pancreas. The deduced amino acid sequence revealed that PAP was synthetized as a preprotein with, in its mature form, a predicted molecular weight of 16,630. A search in protein data bases revealed a marked homology with the carbohydrate binding region of animal lectins; no hemagglutination activity could be shown for PAP, but the protein induced extensive bacterial aggregation. In healthy rats, the very low level of PAP expression in pancreas could be increased up to 4-fold by physiological stimuli such as chronic hormonal or cholinergic stimulation of pancreatic secretion and adaptation of rats to a carbohydrate-rich diet. By contrast, induction of acute experimental pancreatitis by retrograde injection of sodium taurocholate resulted in dramatic overexpression. Pancreatic concentration of PAP mRNA increased more than 300 x within 12 h whereas concentrations of mRNAs encoding major secretory proteins such as amylase decreased. PAP overexpression persisted during the 2 days of the acute phase and then returned to the control level during pancreatic recovery. PAP mRNA could not be evidenced in liver, stomach, salivary glands, brain, kidney, or testis. Its pattern of expression during severe pancreatic aggression suggests that it might be a stress protein involved in the control of bacterial proliferation.

PAP, a pancreatic secretory protein induced during acute pancreatitis, is expressed in rat intestine.

The pancreatitis-associated protein (PAP) is a lectin-related secretory protein present in small amounts in the rat pancreas and rapidly overexpressed during the acute phase of pancreatitis. We demonstrate in this report that PAP is also expressed in rat intestine. A cDNA library from rat jejunum was probed with pancreatic PAP cDNA. The inserts of the selected recombinant clones corresponded to a transcript whose nucleotide sequence was identical to that of pancreatic PAP mRNA. The transcript was detected in duodenum, jejunum, ileum, and colon. A protein with same molecular mass (16 kDa) and pI (8.2) as pancreatic PAP was actually immunodetected in ileum homogenate after separation by two-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Intestinal PAP was immunolocalized to the epithelial cells of the lower part of the villi. The protein accounted respectively for 0.02, 0.05, and 0.1% of soluble proteins in duodenum, jejunum, and ileum homogenates, as measured by enzyme-linked immunosorbent assay, and could not be detected in stomach and colon. Influence of fasting and feeding on PAP mRNA concentration was analyzed in ileum. Concentration decreased by 81 and 94% after animals were fasted for 24 and 48 h, respectively. Feeding restored the initial content within 6 h. On the other hand, intestinal PAP mRNA concentration was not altered during acute pancreatitis.

A novel exocrine protein associated with pancreas transplantation in humans.

After pancreas transplantation, signs of acute pancreatitis are found in the grafted tissue. Pancreatic juice secreted from this organ was analyzed by gel electrophoresis. Initially, the pattern of secretory proteins was similar to that of the juice collected from normal individuals, but high levels of albumin were present. Within 2 days after reperfusion of the grafted pancreas, proteins of molecular weights 17,000-20,000 increased remarkably. Separation by two-dimensional gel electrophoresis showed that this was largely due to the appearance of new a protein, present neither in the juice collected immediately after reperfusion nor in normal pancreatic juice. After transfer onto nitrocellulose, this additional protein was detected by antibodies directed against the recently described rat "pancreatitis-associated protein." Maximal amounts of approximately 7.5% of total secretory protein were found 5 days after transplantation. The concentration of the protein decreased in the further course but was still detectable after 45 days. The isoelectric point (7.1) and the molecular weight (17,500) were similar to those of the rat protein. It is concluded that after inflammation induced by pancreatic transplantation, the human pancreas secretes high amounts of a protein not present in normal juice. Because of its similarities to the rat pancreatitis-associated protein it is designated human pancreatitis-associated protein.