Protein kinase C mu is negatively regulated by 14-3-3 signal transduction proteins.
Recent studies have documented direct interaction between 14-3-3 proteins and key molecules in signal transduction pathways like Ras, Cbl, and protein kinases. In T cells, the 14-3-3tau isoform has been shown to associate with protein kinase C theta and to negatively regulate interleukin-2 secretion. Here we present data that 14-3-3tau interacts with protein kinase C mu (PKCmu), a subtype that differs from other PKC members in structure and activation mechanisms. Specific interaction of PKCmu and 14-3-3tau can be shown in the T cell line Jurkat by immunocoprecipitiation and by pulldown assays of either endogenous or overexpressed proteins using PKCmu-specific antibodies and GST-14-3-3 fusion proteins, respectively. Using PKCmu deletion mutants, the 14-3-3tau binding region is mapped within the regulatory C1 domain. Binding of 14-3-3tau to PKCmu is significantly enhanced upon phorbol ester stimulation of PKCmu kinase activity in Jurkat cells and occurs via a Cbl-like serine containing consensus motif. However, 14-3-3tau is not a substrate of PKCmu. In contrast 14-3-3tau strongly down-regulates PKCmu kinase activity in vitro. Moreover, overexpression of 14-3-3tau significantly reduced phorbol ester induced activation of PKCmu kinase activity in intact cells. We therefore conclude that 14-3-3tau is a negative regulator of PKCmu in T cells.
Hausser
A
A
Institute of Cell Biology and Immunology, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany.
Storz
P
P
Link
G
G
Stoll
H
H
Liu
Y C
YC
Altman
A
A
Pfizenmaier
K
K
Johannes
F J
FJ
D048948:14-3-3 Proteins; D001665:Binding Sites; D015536:Down-Regulation; D006801:Humans; D019169:Jurkat Cells; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000502:physiology*; D012694:Serine / Q000378:metabolism; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000201:enzymology; D014162:Transfection; D014446:Tyrosine 3-Monooxygenase
D048948:14-3-3 Proteins; D011506:Proteins; D012694:Serine; D014446:Tyrosine 3-Monooxygenase; C089212:protein kinase D; D011493:Protein Kinase C