Isolation of a novel prolactin-like cDNA clone from developing rat placenta

Area of Science:

• Reproductive Biology
• Endocrinology
• Molecular Biology

Background:

• The rat placenta expresses several moderately abundant proteins during mid- to late-term pregnancy.
• Rat placental lactogen II (rPLII) is one such identified protein.

Purpose of the Study:

• To isolate and characterize cDNA clones of a novel placental protein, designated rat prolactin-like protein A (rPLP-A).
• To investigate the expression pattern and structural characteristics of rPLP-A.

Main Methods:

• Isolation and characterization of cDNA clones for rPLP-A.
• Analysis of mRNA transcript length and temporal expression during pregnancy.
• In vitro translation and protein processing using dog pancreatic microsomes.
• Deduction of amino acid sequence from nucleotide sequence and homology analysis.

Main Results:

• A single mRNA transcript of 1 kilobase for rPLP-A was identified, appearing at Day 14 of pregnancy.
• In vitro translation yielded a 25,000-dalton protein, processed to 27,000 daltons.
• The deduced amino acid sequence revealed a 196-amino acid secreted protein with two potential glycosylation sites.
• rPLP-A exhibited over 40% amino acid homology to rat prolactin, human prolactin, and rPLII.

Conclusions:

• Rat placenta produces considerable amounts of previously undescribed prolactin-like proteins in late term.
• rPLP-A represents a significant new member of the prolactin-like protein family in rats.
• The findings contribute to understanding placental protein expression and hormonal regulation during pregnancy.