scholarly journals Protein Kinase C-ζ Phosphorylates Insulin Receptor Substrate-1, -3, and -4 But Not -2: Isoform Specific Determinants of Specificity in Insulin Signaling

Endocrinology ◽  
2008 ◽  
Vol 149 (5) ◽  
pp. 2451-2458 ◽  
Author(s):  
Sihoon Lee ◽  
Edward G. Lynn ◽  
Jeong-a Kim ◽  
Michael J. Quon
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Insulin Receptor ◽  
Negative Feedback ◽  
Insulin Signaling ◽  
Kinase Assay ◽  
Insulin Receptor Substrate ◽  
Kinase C ◽  
Pi3k Activity ◽  
Pkc Ζ

Protein kinase C-ζ, a downstream effector of phosphatidylinositol 3-kinase (PI3K), phosphorylates insulin receptor substrate (IRS)-1 on serine residues impairing activation of PI3K in response to insulin. Because IRS-1 is upstream from PI3K, this represents a negative feedback mechanism that may contribute to signal specificity in insulin action. To determine whether similar feedback pathways exist for other IRS isoforms, we evaluated IRS-2, -3, and -4 as substrates for PKC-ζ. In an in vitro kinase assay, purified recombinant PKC-ζ phosphorylated IRS-1, -3 and -4 but not IRS-2. Similar results were obtained with an immune-complex kinase assay demonstrating that wild-type, but not kinase-deficient mutant PKC-ζ, phosphorylated IRS-1, -3, and -4 but not IRS-2. We evaluated functional consequences of serine phosphorylation of IRS isoforms by PKC-ζ in NIH-3T3IR cells cotransfected with epitope-tagged IRS proteins and either PKC-ζ or empty vector control. Insulin-stimulated IRS tyrosine phosphorylation was impaired by overepxression of PKC-ζ for IRS-1, -3, and -4 but not IRS-2. Significant insulin-stimulated increases in PI3K activity was coimmunoprecipitated with all IRS isoforms. In cells overexpressing PKC-ζ there was marked inhibition of insulin-stimulated PI3K activity associated with IRS-1, -3 and -4 but not IRS-2. That is, PI3K activity associated with IRS-2 in response to insulin was similar in control cells and cells overexpressing PKC-ζ. We conclude that IRS-3 and -4 are novel substrates for PKC-ζ that may participate in a negative feedback pathway for insulin signaling similar to IRS-1. The inability of PKC-ζ to phosphorylate IRS-2 may help determine specific functional roles for IRS-2.

Protein kinase C-ζ modulates thromboxane A2-mediated apoptosis in adult ventricular myocytes via Akt

2002 ◽  
Vol 282 (1) ◽  
pp. H320-H327 ◽  
Author(s):  
Yukitaka Shizukuda ◽  
Peter M. Buttrick
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Cardiac Myocytes ◽  
Ventricular Myocytes ◽  
Kinase Assay ◽  
Dependent Manner ◽  
Adult Rat ◽  
Kinase C ◽  
Adult Cardiac Myocytes ◽  
Pkc Ζ

We hypothesized that thromboxane A2 (TxA2) receptor stimulation directly induces apoptosis in adult cardiac myocytes. To investigate this, we exposed cultured adult rat ventricular myocytes (ARVM) to a TxA2 mimetic [1S-[1α,2α(Z),3β(1E,3S*),4α]]-7-[3-[3-hydroxy-4-(4-iodophenoxy)-1-butenyl]-7-oxabicyclo[2.2.1]hept-2-yl]-5-heptenoic acid (I-BOP) for 24 h. Stimulation with I-BOP induced apoptosis in a dose-dependent manner and was completely prevented by a TxA2 receptor antagonist, SQ-29548. We further investigated the role of protein kinase C (PKC) in this process. TxA2 stimulation resulted in membrane translocation of PKC-ζ but not PKC-α, -βII, -δ, and -ε at 3 min and 1 h. The activation of PKC-ζ by I-BOP was confirmed using an immune complex kinase assay. Treatment of ARVM with a cell-permeable PKC-ζ pseudosubstrate peptide (ζ-PS) significantly attenuated apoptosis by I-BOP. In addition, I-BOP treatment decreased baseline Akt activity and its decrease was reversed by treatment with ζ-PS. The inhibition of phosphatidylinositol 3-kinase upstream of Akt by wortmannin or LY-294002 abolished the antiapoptotic effect of ζ-PS. Therefore, our results suggest that the activation of PKC-ζ modulates TxA2 receptor-mediated apoptosis at least, in part, through Akt activity in adult cardiac myocytes.

scholarly journals Shp2 Is Required for Protein Kinase C-dependent Phosphorylation of Serine 307 in Insulin Receptor Substrate-1

2005 ◽  
Vol 280 (38) ◽  
pp. 32693-32699 ◽  
Author(s):  
Karsten Müssig ◽  
Harald Staiger ◽  
Hendrik Fiedler ◽  
Klaus Moeschel ◽  
Alexander Beck ◽  
...  
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Insulin Receptor ◽  
Insulin Receptor Substrate ◽  
Insulin Receptor Substrate 1 ◽  
Kinase C

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

2000 ◽  
Vol 347 (3) ◽  
pp. 781-785 ◽  
Author(s):  
Paulus C. J. VAN DER HOEVEN ◽  
José C. M. VAN DER WAL ◽  
Paula RUURS ◽  
Wim J. VAN BLITTERSWIJK
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Mitogen Activated Protein Kinase ◽  
Kinase Assay ◽  
Kinase C ◽  
Mitogen Activated Protein ◽  
Dose Dependent Fashion ◽  
Acidic Proteins ◽  
Pkc Ζ

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)-ζ and facilitate coupling of PKC-ζ 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-ζ activity. Using recombinant 14-3-3 proteins and purified PKC-ζ in a convenient, newly developed in vitro kinase assay, we found that 14-3-3 proteins stimulated PKC-ζ activity in a dose-dependent fashion up to approx. 2.5-fold. Activation of PKC-ζ by 14-3-3 isotypes was unrelated to their mutual affinity, estimated by co-immunoprecipitation from COS cell lysates. Accordingly, PKC-ζ with a defective (point-mutated) 14-3-3-binding site, showed the same 14-3-3-stimulated activity as wild-type PKC-ζ. As 14-13-3 proteins are acidic, we tested several other acidic proteins, which turned out to stimulate PKC-ζ activity in a similar fashion, whereas neutral or basic proteins did not. These effects were not restricted to the atypical PKC-ζ, 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.

scholarly journals The Role of the Cullin-5 E3 Ubiquitin Ligase in the Regulation of Insulin Receptor Substrate-1

2012 ◽  
Vol 2012 ◽  
pp. 1-8
Author(s):  
Christine Zhiwen Hu ◽  
Jaswinder K. Sethi ◽  
Thilo Hagen
Keyword(s):  
Protein Kinase C ◽  
Protein Kinase ◽  
Insulin Receptor ◽  
Ubiquitin Ligases ◽  
Insulin Receptor Substrate ◽  
E3 Ubiquitin Ligases ◽  
Kinase C ◽  
Cullin 5 ◽  
Socs Proteins ◽  
Protein Kinase C Activation

Background. SOCS proteins are known to negatively regulate insulin signaling by inhibiting insulin receptor substrate-1 (IRS1). IRS1 has been reported to be a substrate for ubiquitin-dependent proteasomal degradation. Given that SOCS proteins can function as substrate receptor subunits of Cullin-5 E3 ubiquitin ligases, we examined whether Cullin-5 dependent ubiquitination is involved in the regulation of basal IRS1 protein stability and signal-induced IRS1 degradation.Findings. Our results indicate that basal IRS1 stability varies between cell types. However, the Cullin-5 E3 ligase does not play a major role in mediating IRS1 ubiquitination under basal conditions. Protein kinase C activation triggered pronounced IRS1 destabilization. However, this effect was also independent of the function of Cullin-5 E3 ubiquitin ligases.Conclusions. In conclusion, SOCS proteins do not exert a negative regulatory effect on IRS1 by functioning as substrate receptors for Cullin-5-based E3 ubiquitin ligases both under basal conditions and when IRS1 degradation is induced by protein kinase C activation.

scholarly journals Phosphorylation of Ser357of Rat Insulin Receptor Substrate-1 Mediates Adverse Effects of Protein Kinase C-δ on Insulin Action in Skeletal Muscle Cells

2008 ◽  
Vol 283 (17) ◽  
pp. 11226-11233 ◽  
Author(s):  
Rizwana Sanaullah Waraich ◽  
Cora Weigert ◽  
Hubert Kalbacher ◽  
Anita M. Hennige ◽  
Stefan Z. Lutz ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Protein Kinase C ◽  
Protein Kinase ◽  
Adverse Effects ◽  
Insulin Receptor ◽  
Insulin Action ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Insulin Receptor Substrate ◽  
Kinase C
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