Cb. Cohick et al., PROLACTIN-LIKE PROTEIN-B - HETEROLOGOUS EXPRESSION AND CHARACTERIZATION OF PLACENTAL AND DECIDUAL SPECIES, Journal of Endocrinology, 152(2), 1997, pp. 291-302
Prolactin-like protein-B (PLP-B) is a member of a family of proteins e
xpressed by the rat placenta and/or decidua with characteristics simil
ar to prolactin (PRL). In this report, we present the heterologous exp
ression and characterization of PLP-B. Recombinant PLP-B heterologousl
y expressed in Chinese hamster ovary cells exhibited similar immunorea
ctive and electrophoretic characteristics with PLP-B produced by rat p
lacental and decidual tissues. N-terminal sequencing verified the iden
tity and purity oi the recombinant PLP-B species and the site of cleav
age of the signal peptide from the mature secreted PLP-B species. Poly
clonal antibodies were generated to the recombinant PLP-B and used for
Western blot and immunocytochemical analyses. Recombinant and native
PLP-B migrated as a doublet at 30-31 kDa in SDS-PAGE under reducing co
nditions. Treatment of recombinant and native PLP-B with N-glycanase a
ccelerated their electrophoretic mobility, indicative of their glycopr
otein nature. PLP-B was localized exclusively to decidual cells in the
developing deciduum and spongiotrophoblast cells in the placental jun
ctional zone. The level of PLP-B protein expression dramatically decli
ned prior to parturition; Potential PRL-like biological actions of PLP
-B were also investigated. PLP-B bound weakly to ovarian and liver PRL
receptors and did not stimulate the proliferation of lactogen-depende
nt Nb2 lymphoma cells. In conclusion, recombinant PLP-B possesses char
acteristics similar to native decidual and placental PLP-B and may rep
resent a hormone/cytokine that has important modulatory actions during
the establishment of pregnancy and the initiation of parturition.