Project description:This SuperSeries is composed of the following subset Series: GSE33149: Substrate selectivity for semisynthetic CK2 proteins with various posttranslational modifications GSE33150: Substrate selectivity for semisynthetic CK2 proteins with Pin1 Refer to individual Series
Project description:Akt is a Ser/Thr protein kinase that regulates cell growth, metabolism and is considered a therapeutic target for cancer. Regulation of Akt by membrane recruitment and post-translational modifications (PTMs) has been extensively studied. The most well-established mechanism for cellular Akt activation involves phosphorylation on its activation loop on Thr308 by PDK1 and on its C-terminal tail on Ser473 by mTORC2. Other C-terminal tail PTMs have been identified, but their functional impacts have not been well-characterized. We use expressed protein ligation (EPL) as a tool to produce semisynthetic Akt proteins to dissect the enzymatic functions of these PTMs. We performed kinase assays employing human protein microarrays to investigate global substrate specificity of Akt, comparing phosphorylated vs. O-GlcNAcylated Ser473 forms.
Project description:Protein Ser/Thr kinase CK2 is involved in a myriad of cellular processes including cell growth and proliferation by phosphorylating hundreds of substrates, yet the regulation process of CK2 function is poorly understood. The CK2 catalytic subunit, CK2α, is phosphorylated at Thr344 and phosphorylation on the C-terminal tail of CK2α is required for interaction with Pin1 protein. The substrate selectivity for protein kinase CK2α was examined by performing kinase assays on protein microarrays spotted with 17,000 human proteins. Semisynthetic CK2α proteins were prepared to contain an unmodified C-terminal tail or phospho-Thr (pThr) at T344. These semisynthetic proteins were used to determine if the phosphorylation-dependent interaction of CK2α with Pin1 can modulate the substrate selectivity for CK2. The different semisynthetic CK2α proteins (unmodified and pThr344) were tested alone and in the presence of the recombinant Pin1 protein. Pin1 has been shown to interaction with CK2α only when CK2α is phoshorylated on its C-terminal site (including Thr344). In the study presented here, kinase assays were performed using two different semisynthetic CK2α proteins: unmodified C-terminal tail and phospho-Thr (pThr) at 344. The semisynthetic proteins were each tested alone and in the presence of the recombinant Pin1 protein. There were four different kinase conditions and each condition was performed in duplicate.
Project description:Protein Ser/Thr kinase CK2 is involved in a myriad of cellular processes including cell growth and proliferation by phosphorylating hundreds of substrates, yet the regulation process of CK2 function is poorly understood. The CK2 catalytic subunit, CK2α, is phosphorylated at Thr344 and phosphorylation on the C-terminal tail of CK2α is required for interaction with Pin1 protein. The substrate selectivity for protein kinase CK2α was examined by performing kinase assays on protein microarrays spotted with 17,000 human proteins. Semisynthetic CK2α proteins were prepared to contain an unmodified C-terminal tail or phospho-Thr (pThr) at T344. These semisynthetic proteins were used to determine if the phosphorylation-dependent interaction of CK2α with Pin1 can modulate the substrate selectivity for CK2. The different semisynthetic CK2α proteins (unmodified and pThr344) were tested alone and in the presence of the recombinant Pin1 protein. Pin1 has been shown to interaction with CK2α only when CK2α is phoshorylated on its C-terminal site (including Thr344).
Project description:Protein Ser/Thr kinase CK2 is involved in a myriad of cellular processes including cell growth and proliferation by phosphorylating hundreds of substrates, yet the regulation process of CK2 function is poorly understood. The CK2 catalytic subunit, CK2α, is modified by O-GlcNAc on Ser347 proximal to a Cdk1 phosphorylation site at Thr344 on the same protein. The substrate selectivity for protein kinase CK2 was examined by performing kinase assays on protein microarrays spotted with 17,000 human proteins. Semisynthetic CK2α proteins were prepared to contain an unmodified C-terminal tail, S-GlcNAc-Serine at S347, or Pfa (non-hyrdolyzeable phosphomimic) at T344. These semisynthetic proteins were used to determine if the posttranslational modifications on CK2 alpha modulate the substrate selectivity for this pleiotropic kinase. The different semisynthetic CK2α proteins were tested alone and in the presence of the regulatory subunit CK2β since it is known that the CK2α subunit is active both in its isolated state and in the heterotetrameric state formed in the presence of the regulatory beta subunit. The CK2β subunit has been shown to modulate CK2 activity with some substrates and not others. In the study presented here, kinase assays were performed using three different semisynthetic CK2 alpha proteins: unmodified C-terminal tail; S-GlcNAc-Ser at 347; and Pfa (phosphomimic) at 344. The semisynthetic proteins were each tested alone and in the presence of the regualatory CK2 beta subunit. There were six different kinase conditions and each condition was performed in duplicate and one no kinase control was performed to eliminate autophorylated proteins.
Project description:Protein Ser/Thr kinase CK2 is involved in a myriad of cellular processes including cell growth and proliferation by phosphorylating hundreds of substrates, yet the regulation process of CK2 function is poorly understood. The CK2 catalytic subunit, CK2α, is modified by O-GlcNAc on Ser347 proximal to a Cdk1 phosphorylation site at Thr344 on the same protein. The substrate selectivity for protein kinase CK2 was examined by performing kinase assays on protein microarrays spotted with 17,000 human proteins. Semisynthetic CK2α proteins were prepared to contain an unmodified C-terminal tail, S-GlcNAc-Serine at S347, or Pfa (non-hyrdolyzeable phosphomimic) at T344. These semisynthetic proteins were used to determine if the posttranslational modifications on CK2 alpha modulate the substrate selectivity for this pleiotropic kinase. The different semisynthetic CK2α proteins were tested alone and in the presence of the regulatory subunit CK2β since it is known that the CK2α subunit is active both in its isolated state and in the heterotetrameric state formed in the presence of the regulatory beta subunit. The CK2β subunit has been shown to modulate CK2 activity with some substrates and not others.
Project description:mTOR complex 2 (mTORC2) phosphorylates AKT in a hydrophobic motif site that is a biomarker of insulin sensitivity. In adipocytes, mTORC2 regulates glucose and lipid metabolism; however, the mechanism has been unclear because downstream AKT signaling appears unaffected by mTORC2 loss. Here, by applying immunoblotting, targeted phosphoproteomics and metabolite profiling in brown preadipocytes, we identify ATP-citrate lyase (ACLY) as a distinctly mTORC2-sensitive AKT substrate. mTORC2 appears dispensable for most other AKT actions examined indicating a previously unappreciated selectivity in mTORC2-AKT signaling. Rescue experiments show brown preadipocytes require the mTORC2/AKT/ACLY pathway to induce PPAR-gamma and establish the epigenetic landscape during differentiation. mTORC2 also acts through ACLY in mature brown adipocytes to increase ChREBP activity, histone acetylation, and gluco-lipogenic gene expression. Substrate utilization studies additionally implicate mTORC2 in promoting acetyl-CoA synthesis from acetate through acetyl-CoA synthetase 2 (ACSS2). These data suggest that a principal mTORC2 action is controlling nuclear-cytoplasmic acetyl-CoA synthesis.
Project description:Quantitative glycoproteomics reveals cellular substrate selectivity of the endoplasmic reticulum protein quality control sensors UGGT1 and UGGT2
Project description:The phosphoinositide 3-kinase (PI3K)-Akt network is tightly controlled by feedback mechanisms that regulate signal flow and ensure signal fidelity. Here, we show that Akt itself engages negative feedback by phosphorylating insulin receptor substrate (IRS) 1 and 2 on a number of residues. Mechanistically this serves to deplete plasma membrane-localised IRS1/2 and reduce its interaction with the insulin receptor. Together these events limit plasma membrane associated PI3K and phosphatidylinositol (3,4,5)-trisphosphate (PIP3) synthesis. We identified two Akt-dependent phosphorylation sites in IRS2 at S306 (S303 in mouse) and S577 (S573 in mouse) that are key drivers of this negative feedback. These findings establish another mechanism by which the kinase Akt auto-regulates its activity, through post-translational modification of the IRS scaffold that in turn controls PIP3 levels.