Retinoic acid stimulates the protein kinase C pathway before activation of its beta-nuclear receptor during human teratocarcinoma differentiation.
We previously reported that protein kinase C (PKC) stimulation through phorbol ester (TPA) treatment enhances the effects of all-trans retinoic acid (RA) on immunophenotypic differentiation and RA nuclear receptor (RAR) activation in the multipotential human teratocarcinoma (TC) cell line NTera-2/clone D1 (abbreviated NT2/D1). This study extends prior work in NT2/D1 cells by demonstrating that PKC pathway activation is an early effect of RA treatment which regulates RAR transcriptional activity. RA activated the PKC pathway prior to induction of RAR-beta expression at 6 h, which is an established early marker of RAR activation in NT2/D1 cells. RA caused a transient 1.3-fold increase in intracellular diacylglycerol (DG) at 2 min and a translocation of the gamma isozyme of PKC (PKC-gamma) within 5 min. Transient co-transfection studies provided evidence that PKC pathway activation plays a role in the regulation of RAR-beta expression. In these studies a constitutively active PKC-gamma augmented the RA-mediated transactivation of a luciferase reporter containing the native RAR-beta promoter which has a retinoic-acid-response element (RARE). These findings reveal that PKC pathway activation is an early step in RA-mediated human TC differentiation and that PKC-gamma can potentiate the effects of RA on RAR transcriptional activation.
Kurie
J M
JM
Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY 10021.
Younes
A
A
Miller
W H
WH
Burchert
M
M
Chiu
C F
CF
Kolesnick
R
R
Dmitrovsky
E
E
D002454:Cell Differentiation; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004075:Diglycerides / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D011493:Protein Kinase C / Q000378:metabolism*; D018243:Teratocarcinoma / Q000473:pathology*; D014212:Tretinoin / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects
D004075:Diglycerides; D014212:Tretinoin; D011493:Protein Kinase C