The six-
cysteine P-domain motif forms the basic repeat unit of a growing family of
mucin-associated
peptides. A precursor for a human secretory
polypeptide has been discovered by molecular cloning and deduced to have a single P-domain, termed hP1.B. The pre-pro-
peptide has 67%
amino acid identity with
rat intestinal trefoil factor. We find, using the techniques of
RNA analysis and in situ hybridization, that this P-domain peptide is expressed in the human gastrointestinal tract, where a number of pathological conditions affect its expression, and surprisingly find it is expressed in the uterus also. In the intestine, hP1.B is expressed by goblet cells, but in
Crohn disease this
peptide is synthesized and secreted additionally by the
ulcer-associated cell lineage that is known to secrete two other
trefoil peptides, pS2 and
spasmolytic polypeptide (hSP). In the stomach, hP1.B
mRNA is relatively scarce but is more abundant in foci of intestinal
metaplasia and near to ulceration.
Mucin-rich epithelial cells in hyperplastic
polyps of the colon also express this
peptide. The discovery of this P-domain peptide and its expression in association with
mucins support the hypothesis that P-domains with
mucins may subserve related functions in the maintenance and repair of mucosal function.