Complementary DNA cloning and regulation of expression of the messenger RNA encoding a pregnancy-associated porcine uterine protein related to human antileukoproteinase.

Antileukoproteinase (ALP) is a low mol wt mucosal secretory protein which, in human tissues, inhibits the activities of the neutral serine lysosomal proteinases elastase and cathepsin-G. In this study a number of recombinant cDNA clones corresponding to porcine ALP (pALP) were isolated from a cDNA library prepared from porcine endometrial poly(A)+ RNAs. The combined nucleotide sequences of the cDNA clones, representing the entire pALP mRNA sequence, are approximately 600 nucleotides long and encode a protein of 114 amino acids. The deduced amino acid sequence of pALP is 68% similar in primary structure to that of human ALP, is cysteine and proline rich, and exhibits a two-domain structure which, in the human protein, is involved in binding trypsin/cathepsin-G and elastase, respectively. However, pALP appears to lack the internal signal sequence of the corresponding human protein. Northern blot analysis of uterine RNAs using pALP cDNAs as probe demonstrated a single mRNA species approximately 0.8 kilobase in length. Uterine expression of pALP mRNA was highest in mid- and late pregnancy and very low or undetectable in early pregnancy. Estrogen and progesterone increased the levels of uterine pALP mRNA in prepubertal gilts, but not to the levels obtained at mid- and late gestation. pALP mRNA was also abundant in adult pig lung, where its expression was constitutive. Lower levels of pALP were found in fetal and neonatal lung and small intestine and in maternal cervix, spleen, and small intestine. Our study on the molecular cloning and analysis of pALP mRNA represents the first report on the porcine proteinase inhibitor and extends the identification of pregnancy-associated uterine proteins, which may play important functions in embryo or fetal development. The control of expression of pALP mRNA, which is distinct from those of other porcine uterine proteins studied to date, should provide additional insights into the mechanisms of regulation of uterine secretory activity.