Identification and characterization of a new member of the prolactin family, placental lactogen-I variant.


This report describes the identification and characterization of a new member of the placental prolactin (PRL) family, termed placental lactogen-I variant (PL-Iv). PL-Iv was isolated from medium conditioned by late gestation placental explants. Rat PL-Iv was found to be closely related to rat PL-I. Amino-terminal sequence analysis indicated that PL-Iv shared approximately 88% sequence identity with the amino terminus of PL-I. PL-Iv proteins cross-reacted with antiserum to recombinant mouse PL-I and PL-Iv mRNA hybridized with a PL-I cDNA. Multiple PL-I and PL-Iv species were present in placental cytosol. Despite the structural similarities between PL-I and PL-Iv, distinct differences were also evident. Antibodies generated to the amino-terminal 19 amino acids of PL-Iv specifically recognized PL-Iv, while failing to recognize PL-I. Secreted PL-Iv had an affinity for concanavalin A, whereas secreted PL-I lacked affinity for the lectin. PL-I was predominantly secreted as a 36-40-kDa species and PL-Iv was predominantly secreted as a 33-kDa species. Furthermore, PL-I and PL-Iv were synthesized at different times during gestation and by different cell types. PL-I was synthesized by trophoblast giant cells during the first half of gestation, while PL-Iv was predominantly synthesized by spongiotrophoblast cells during the later stages of gestation. PL-Iv was shown to stimulate the proliferation of rat Nb2 lymphoma cells, an in vitro measure of lactogenic activity. In summary, PL-Iv shares structural similarities with PL-I; however, it shows other structural differences in addition to unique cell- and temporal-specific patterns of expression in the rat chorioallantoic placenta.


Citations per Year

143 Citations

Semantic Scholar estimates that this publication has 143 citations based on the available data.

See our FAQ for additional information.

Cite this paper

@article{Deb1991IdentificationAC, title={Identification and characterization of a new member of the prolactin family, placental lactogen-I variant.}, author={Santanu Deb and Teresa Faria and Katherine F. Roby and Dorrit Bjerg Larsen and Stanley C Kwok and Frank J Talamantes and Michael J. Soares}, journal={The Journal of biological chemistry}, year={1991}, volume={266 3}, pages={1605-10} }