Protein kinase C activation by acidic proteins including 14-3-3

Abstract

14-3-3 proteins may function as adapter or scaffold proteins in signal transduction pathways. We reported previously that several 14-3-3 isotypes bind to protein kinase C (PKC)-zeta and facilitate coupling of PKC-zeta to Raf-1 [van der Hoeven, van der Wal, Ruurs, van Dijk and van Blitterswijk (2000) Biochem. J. 345, 297-306], an event that boosts the mitogen-activated protein kinase (ERK) pathway in Rat-1 fibroblasts. The present work investigated whether bound 14-3-3 would affect PKC-zeta activity. Using recombinant 14-3-3 proteins and purified PKC-zeta in a convenient, newly developed in vitro kinase assay, we found that 14-3-3 proteins stimulated PKC-zeta activity in a dose-dependent fashion up to approx. 2.5-fold. Activation of PKC-zeta by 14-3-3 isotypes was unrelated to their mutual affinity, estimated by co-immunoprecipitation from COS cell lysates. Accordingly, PKC-zeta with a defective (point-mutated) 14-3-3-binding site, showed the same 14-3-3-stimulated activity as wild-type PKC-zeta. As 14-13-3 proteins are acidic, we tested several other acidic proteins, which turned out to stimulate PKC-zeta activity in a similar fashion, whereas neutral or basic proteins did not. These effects were not restricted to the atypical PKC-zeta, but were also found for classical PKC. Together, the results suggest that the stimulation of PKC activity by 14-3-3 proteins is non-specific and solely due to the acidic nature of these proteins, quite similar to that known for acidic lipids.

Regulation of Protein Kinase C function by phosphorylation on conserved and non-conserved sites

“…Spatial and temporal control of PKC signalling is also influenced via interaction with adaptor/scaffolding proteins that anchor the PKCs to various intracellular locations in the cell. A multitude of adaptor proteins that influence PKC function have been characterised, including A-Kinase Anchoring Proteins (AKAPs) [15,16], Receptors for Activated C Kinases (RACKs) [17,18] and 14-3-3 proteins [19,20]. Termination of PKC signalling is best described for cPKCs and nPKCs.…”

The Saccharomyces cerevisiae 14-3-3 Proteins Are Required for the G1/S Transition, Actin Cytoskeleton Organization and Cell Wall Integrity

“…Moreover, 14-3-3 proteins have been implicated also in Ras/MAPK cascade signaling in vertebrates (Fantl et al 1994;Li et al 1995) and during pseudohyphal development in S. cerevisiae (Roberts et al 1997). Finally, vertebrate 14-3-3 proteins were shown to inhibit or activate protein kinase C (PKC), which is involved in many signaling processes (Toker et al 1990;Isobe et al 1992;Tanji et al 1994), and to stimulate the interaction between PKC and the mitogenstimulated Raf1 kinase that controls cell growth (Van Der Hoeven et al 2000).…”

Differential activation of extracellular signal-regulated kinase 1 and a related complex in neuronal nuclei

“…This protein family can either positively modulate enzyme activity, in the cases of serotonin Nacetyltransferase (Obsil et al 2001) and Protein Kinase C (Van Der Hoeven et al 2000), or negatively modulate activity, such as with CaM-kinase kinase (Davare et al 2004). Specifically in the ERK pathways, 14-3-3 does not impact the activity of MEK (Shimizu et al 1994), but it has been reported to stimulate the enzyme upstream from MEK, Raf (Freed et al 1994) ) and associates with other upstream kinases in the pathway (Yamamori et al 1995).…”