Activation of protein kinase C delta by all-trans-retinoic acid.
All-trans-retinoic acid (RA) is a potent inhibitor of leukemia cell proliferation and induces differentiation of acute promyelocytic leukemia cells in vitro and in vivo. For RA to induce its biological effects in target cells, binding to specific retinoic acid nuclear receptors is required. The resulting complexes bind to RA-responsive elements (RAREs) in the promoters of RA-inducible genes to initiate gene transcription and to generate protein products that mediate the biological effects of RA. In this report, we provide evidence that a member of the protein kinase C (PKC) family of proteins, PKC delta, is activated during RA treatment of the NB-4 and HL-60 acute myeloid leukemia cell lines as well as the MCF-7 breast cancer cell line. Such RA-dependent phosphorylation was also observed in primary acute promyelocytic leukemia cells and resulted in activation of the kinase domain of PKC delta. In studies aimed at understanding the functional relevance of PKC delta in the induction of RA responses, we found that pharmacological inhibition of PKC delta (but not of other PKC isoforms) diminished RA-dependent gene transcription via RAREs. On the other hand, overexpression of a constitutively active form of the kinase strongly enhanced RA-dependent gene transcription via RAREs. Gel shift assays and chromatin immunoprecipitation studies demonstrated that PKC delta associated with retinoic acid receptor-alpha and was present in an RA-inducible protein complex that bound to RAREs. Pharmacological inhibition of PKC delta activity abrogated the induction of cell differentiation and growth inhibition of NB-4 blast cells, demonstrating that its function is required for such effects. Altogether, our data provide strong evidence that PKC delta is activated in an RA-dependent manner and plays a critical role in the generation of the biological effects of RA in malignant cells.
Kambhampati
Suman
S
Robert H. Lurie Comprehensive Cancer Center and the Division of Hematology-Oncology, Northwestern University Feinberg School of Medicine and Lakeside Veterans Affairs Medical Center, Chicago, Illinois 60611, USA.
Li
Yongzhong
Y
Verma
Amit
A
Sassano
Antonella
A
Majchrzak
Beata
B
Deb
Dilip K
DK
Parmar
Simrit
S
Giafis
Nick
N
Kalvakolanu
Dhananjaya V
DV
Rahman
Arshad
A
Uddin
Shahab
S
Minucci
Saverio
S
Tallman
Martin S
MS
Fish
Eleanor N
EN
Platanias
Leonidas C
LC
D002454:Cell Differentiation; D002455:Cell Division; D002843:Chromatin / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D005434:Flow Cytometry; D018922:HL-60 Cells; D006801:Humans; D015151:Immunoblotting; D016898:Interferon-alpha / Q000378:metabolism; D008156:Luciferases / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000378:metabolism*; D051745:Protein Kinase C-delta; D017434:Protein Structure, Tertiary; D018168:Receptors, Retinoic Acid / Q000378:metabolism; D000072482:Retinoic Acid Receptor alpha; D014158:Transcription, Genetic; D014212:Tretinoin / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D002843:Chromatin; D016898:Interferon-alpha; D020033:Protein Isoforms; C000607071:RARA protein, human; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D014212:Tretinoin; D008156:Luciferases; C497258:PRKCD protein, human; D011493:Protein Kinase C; D051745:Protein Kinase C-delta