A cDNA Encoding a New Member of the Rat Placental Lactogen Family, PL-I mosaic (PL-Im).

Abstract

Abstract. We have isolated a cDNA encoding a novel placental lactogen (PL), PL-I mosaic (PL-Im), by screening the cDNA library in ,ZAP of the mid-pregnant (day 12) rat placenta. The cDNA comprised an open reading frame of 687 by encoding 229 amino acids, in which there were two putative Nglycosylation sites. Northern blot analysis showed that PL-Im mRNA was expressed specifically during mid-pregnancy (days 10 and 12) in the rat placenta. The cDNA was highly homologous with those of other rat PL family members; in particular, the homology among PL-Im, PL-I (mid-pregnancy-specific) and PL-Iv (late-pregnancy-specific) was over 90%. Interestingly, the nucleotide sequence of PL-Im cDNA was a mosaic of PL-I and PL-Iv and it did not possess its own particular sequence. As the genomic pattern determined using Southern blot analysis of PL-Im was distinct from that of PL-I and PLIv, the encoded area of PL-Im appears to be independent of those of PL-I and PL-Iv on the gene. In the dendrogram of the rat PL family constructed on the basis of the nucleotide sequence homologies, PL-Im was located between PL-Iv and PL-I in the process of molecular evolution. Therefore, PL-Im has a unique cDNA structure and may be a principal factor in the molecular evolution of PLs.

Characterization of Rat Mid-Pregnancy-Specific Placental Lactogen Produced by Baculovirus / Insect Cell Expression System

“…With the exception of PL-II, all members of the placental PRL family have one or two putative N-glycosylation sites [1], asparagine-Xaa-serine/ threonine (Asn-Xaa-Ser/Thr), where Xaa can be any amino acid except proline. PL-Im has two putative N-glycosylation sites at Asn 79 and Asn 128 [2]. The apparent MW of recPL-Im showed relatively wide range in the Western blot, and it (more than 26 kDa) was bigger than predicted from its nucleotide sequence of the cDNA [2].…”

“…PL-Im has two putative N-glycosylation sites at Asn 79 and Asn 128 [2]. The apparent MW of recPL-Im showed relatively wide range in the Western blot, and it (more than 26 kDa) was bigger than predicted from its nucleotide sequence of the cDNA [2]. In the presence of tunicamycin, the MW was reduced and heterogeneity disappeared, indicating that recPL-Im has N-linked glycoresidue(s).…”

“…PL-Im cDNA has two possible N-glycosylation sites [2], but PLP-D has only one [3]. The recombinant PLP-D do not stimulate the proliferation of the rat lymphoma cell line, Nb2 cells, revealing that this placental PRL-like molecule has activity distinct from that of PRL but the molecular char-T he rat placental PRL family consists of molecules structurally similar to PRL and growth hormone [1].…”

“…The recombinant PLP-D do not stimulate the proliferation of the rat lymphoma cell line, Nb2 cells, revealing that this placental PRL-like molecule has activity distinct from that of PRL but the molecular char-T he rat placental PRL family consists of molecules structurally similar to PRL and growth hormone [1]. We successfully cloned cDNA encoding two members of it, PL-Im and PRL-like protein-D (PLP-D) [2,3]. PL-Im mRNA is expressed at mid-pregnancy in the rat placenta and its structure is highly homologous (over 90%) with PL-I (mid-pregnancy-specific PL) [4] and PL-I variant (PL-Iv) (late-pregnancy-specific PL) [5].…”

An Interspecies Comparison of Placental Gangliosides.

“…togens [5][6][7][8] and expression of plasma membrane proteins [9] and gangliosides [10]. We reported that the major gangliosides present in the rat placenta were GM3 and GD3 [10]: GM3 predominated during mid-pregnancy and its levels declined during late pregnancy, whereas the converse was observed for GD3.…”