Protein kinase C and mammary cell differentiation: involvement of protein kinase C alpha in the induction of beta-casein expression.
Treatment of HC11 mouse mammary epithelial cells with the lactogenic hormones dexamethasone, insulin, and prolactin (DIP) leads to cellular differentiation and production of the milk protein beta-casein. The following experimental evidence suggests the involvement of protein kinase C (PKC) in DIP induced signal transduction. Down-regulation of PKC by 12-O-tetradecanoylphorbol-13-acetate or addition of CGP 41251, a selective inhibitor of PKC, inhibited beta-casein protein expression induced by DIP in HC11 cells. This inhibition occurs at the level of transcription, since the DIP mediated activation of a beta-casein promoter-luciferase reporter construct or of mammary gland specific factor (MGF), an essential transcription factor for beta-casein promoter activity, was also inhibited by CGP 41251. Inhibition or down-regulation of PKC reduced the activation of MGF by prolactin as well. PKC-alpha, the only conventional PKC isoform expressed in HC11 cells, is most likely involved in the DIP induced beta-casein expression. (a) Only PKC-alpha and PKC-epsilon are down-regulated by 12-O-tetradecanoylphorbol-13-acetate whereas PKC-delta and PKC-zeta are not. (b) Of the PKC isoforms expressed in HC11 cells, CGP 41251 inhibits PKC-alpha more potently than PKC-delta, PKC-epsilon, and PKC-zeta. The IC50 for the inhibition of beta-casein synthesis, MGF activation, and beta-casein promoter activity by CGP 41251 correlated well with the IC50 of PKC-alpha inhibition. (c) Finally, only PKC-alpha translocated to membrane fractions after DIP or prolactin treatment. Taken together, these data indicate that PKC-alpha plays an important role in the signaling pathway activated by prolactin during beta-casein induction.
Friedrich Miescher Institute, Basel, Switzerland.
B M
BM
Marte
T
T
Meyer
S
S
Stabel
G J
GJ
Standke
S
S
Jaken
D
D
Fabbro
N E
NE
Hynes
D000470:Alkaloids / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002364:Caseins / Q000096:biosynthesis*; D002454:Cell Differentiation / Q000187:drug effects; D002460:Cell Line; D003907:Dexamethasone / Q000494:pharmacology; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology; D007328:Insulin / Q000494:pharmacology; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000502:physiology*; D008321:Mammary Glands, Animal / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D011247:Pregnancy; D011388:Prolactin / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D051571:Protein Kinase C-alpha; D019311:Staurosporine / Q000031:analogs & derivatives*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000470:Alkaloids; D002364:Caseins; D007328:Insulin; D007527:Isoenzymes; D003907:Dexamethasone; D011388:Prolactin; C496630:Prkca protein, mouse; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha; D019311:Staurosporine; C059539:midostaurin; D013755:Tetradecanoylphorbol Acetate