Expression of kappa-casein in normal and neoplastic rat mammary gland is under the control of prolactin.
An 820-nucleotide-long cDNA clone for the kappa-casein (the casein micelle-stabilizing protein) from rat mammary gland was isolated, and its nucleotide sequence was determined. The deduced amino acid sequence from the nucleotide sequence revealed a signal peptide, 21 amino acids long, and a mature protein of 157 amino acids. The signal peptide of rat kappa-casein was highly homologous to that of the precursor to ovine kappa-casein. However, little homology was apparent when the mature kappa-casein protein sequences from ovine or bovine sources were compared with rat kappa-casein. The kappa-casein mRNA content of the mammary tissue was found to increase during its functional differentiation. Prolactin appears to modulate the production of kappa-casein mRNA. Mammary glands of virgin females had no detectable kappa-casein mRNA; however, a marked induction of kappa-casein mRNA was obtained by intravenous infusion of prolactin. Mammary carcinomas did not follow the same pattern. 7,12-Dimethylbenz[a]anthracene-induced mammary carcinomas had normally low levels of kappa-casein mRNA, but intravenous prolactin infusion increased the levels by 2-fold. The MTW9 mammary carcinoma that grows only in the presence of high levels of mammotropic hormones had kappa-casein mRNA content equivalent to that in 10-day lactating rat mammary gland. Continuous venous infusion of prolactin to MTW9 mammary carcinoma did not modify the kappa-casein mRNA levels. Nitrosomethylurea-induced mammary carcinomas had no detectable kappa-casein mRNA, and intravenous prolactin infusion was unable to induce it.
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001943:Breast Neoplasms / Q000378:metabolism* / Q000473:pathology; D002364:Caseins / Q000235:genetics*; D003001:Cloning, Molecular; D004247:DNA / Q000378:metabolism; D004262:DNA Restriction Enzymes; D005260:Female; D008321:Mammary Glands, Animal / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011388:Prolactin / Q000494:pharmacology*; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D011919:Rats, Inbred Strains; D014158:Transcription, Genetic / Q000187:drug effects
D002364:Caseins; D012333:RNA, Messenger; D011388:Prolactin; D004247:DNA; D004262:DNA Restriction Enzymes