scholarly journals Identification of the S6 kinase activity stimulated in quiescent brine shrimp embryos upon entry to preemergence development as p70 ribosomal protein S6 kinase: Isolation of Artemia franciscana p70S6k cDNA

2001 ◽  
Vol 79 (2) ◽  
pp. 141-152 ◽  
Author(s):  
Jorge Santiago ◽  
Thomas W Sturgill
Keyword(s):  
Brine Shrimp ◽  
Kinase Activity ◽  
State Level ◽  
Artemia Franciscana ◽  
Level Variation ◽  
S6 Kinase ◽  
Ribosomal Subunits ◽  
Ribosomal Protein S6 ◽  
Ribosomal S6 Kinase ◽  
Specific Polyclonal Antibody

We previously demonstrated that a protein kinase responsible for phosphorylating 40S ribosomal subunits is activated in quiescent Artemia franciscana embryos within 15 min of restoration of normal tonicity and incubation at 30°C. Here, we identify the activated S6 kinase as A. franciscana p70 ribosomal S6 kinase (p70S6k) subsequent to the isolation of an Artemia p70S6k cDNA. The protein conceptually translated from cDNA has 70% similarity and 64% identity to both Drosophila melanogaster and human p70S6k. Southern blot analysis is consistent with presence of a single p70S6k gene. Two transcripts of 5.4 and 2.7 kb were found. Abundance of both mRNAs increased dramatically around 4 h of preemergence development, and exhibited different steady-state level variation thereafter. Stimulated S6 kinase activity, partially purified by Superose 6 chromatography, correlated best with the slowest migrating, ~65 kDa, form detected by Western analysis using a specific polyclonal antibody made to a peptide from the predicted p70S6k NH2-terminus. Furthermore, the A. franciscana p70S6k was immunoprecipitated with the same antibody, showing in parallel an S6 kinase activity similar to peak profiles. We conclude that the stimulated S6 kinase activity is that of an ortholog of human p70S6k that may be involved in the regulation of protein synthesis during preemergence development in A. franciscana species.Key Words: p70 ribosomal S6 kinase cDNA, brine shrimp, development.

scholarly journals Two distinct enzymes contribute to biphasic S6 phosphorylation in serum-stimulated chicken embryo fibroblasts.

1990 ◽  
Vol 10 (6) ◽  
pp. 2787-2792 ◽  
Author(s):  
L J Sweet ◽  
D A Alcorta ◽  
R L Erikson
Keyword(s):  
Chicken Embryo ◽  
Kinase Activity ◽  
Chicken Embryo Fibroblast ◽  
Total Serum ◽  
S6 Kinase ◽  
Serum Stimulation ◽  
Ribosomal Protein S6 ◽  
Phosphopeptide Analysis ◽  
Embryo Fibroblasts ◽  
Chicken Embryo Fibroblasts

Serum stimulation of quiescent chicken embryo fibroblasts resulted in a time-dependent, biphasic activation of S6 kinase activity. Chromatographic fractionation of serum-stimulated cell lysates resolved two distinct S6 kinase activities. Anti-Xenopus S6 kinase II antiserum immunoprecipitated a 90,000-Mr S6 kinase but did not cross-react with a smaller, 65,000-Mr S6 kinase. Phosphopeptide analysis confirmed that the 90,000- and 65,000-Mr proteins were structurally unrelated and established that the 65,000-Mr protein isolated by the current protocol was the same serum-stimulated chicken embryo fibroblast S6 kinase as that previously characterized (J. Blenis, C. J. Kuo, and R. L. Erikson, J. Biol. Chem. 262:14373-14376, 1987). These results demonstrate the contribution of two distinct S6 kinases to total serum-stimulated ribosomal protein S6 phosphorylation.

scholarly journals p42 mitogen-activated protein kinase and p90 ribosomal S6 kinase are selectively phosphorylated and activated during thrombin-induced platelet activation and aggregation.

1994 ◽  
Vol 14 (1) ◽  
pp. 463-472 ◽  
Author(s):  
J Papkoff ◽  
R H Chen ◽  
J Blenis ◽  
J Forsman
Keyword(s):  
Signal Transduction ◽  
Platelet Aggregation ◽  
Protein Kinase ◽  
Immune Complex ◽  
Platelet Activation ◽  
Kinase Activity ◽  
Mitogen Activated Protein Kinase ◽  
S6 Kinase ◽  
Mitogen Activated Protein ◽  
Ribosomal S6 Kinase

Human platelets provide an excellent model system for the study of phosphorylation events during signal transduction and cell adhesion. Platelets are terminally differentiated cells that exhibit rapid phosphorylation of many proteins upon agonist-induced activation and aggregation. We have sought to identify the kinases as well as the phosphorylated substrates that participate in thrombin-induced signal transduction and platelet aggregation. In this study, we have identified two forms of mitogen-activated protein kinase (MAPK), p42mapk and p44mapk, in platelets. The data demonstrate that p42mapk but not p44mapk becomes phosphorylated on serine, threonine, and tyrosine during platelet activation. Immune complex kinase assays, gel renaturation assays, and a direct assay for MAPK activity in platelet extracts all support the conclusion that p42mapk but not p44mapk shows increased kinase activity during platelet activation. The activation of p42mapk, independently of p44mapk, in platelets is unique since in other systems, both kinases are coactivated by a variety of stimuli. We also show that platelets express p90rsk, a ribosomal S6 kinase that has previously been characterized as a substrate for MAPK. p90rsk is phosphorylated on serine in resting platelets, and this phosphorylation is enhanced upon thrombin-induced platelet activation. Immune complex kinase assays demonstrate that the activity of p90rsk is markedly increased during platelet activation. Another ribosomal S6 protein kinase, p70S6K, is expressed by platelets but shows no change in kinase activity upon platelet activation with thrombin. Finally, we show that the increased phosphorylation and activity of both p42mapk and p90rsk does not require integrin-mediated platelet aggregation. Since platelets are nonproliferative cells, the signal transduction pathways that include p42mapk and p90rsk cannot lead to a mitogenic signal and instead may regulate cytoskeletal or secretory changes during platelet activation.

scholarly journals p90 ribosomal S6 kinase 2 is associated with and dephosphorylated by protein phosphatase 2Cδ

2004 ◽  
Vol 382 (2) ◽  
pp. 425-431 ◽  
Author(s):  
Ulrik DOEHN ◽  
Steen GAMMELTOFT ◽  
Shi-Hsiang SHEN ◽  
Claus J. JENSEN
Keyword(s):  
Protein Phosphatase ◽  
Kinase Activity ◽  
Kinase Domain ◽  
Protein Kinase Activity ◽  
Dependent Manner ◽  
S6 Kinase ◽  
Ribosomal S6 Kinase 2 ◽  
P90 Ribosomal S6 Kinase ◽  
Ribosomal S6 Kinase

RSK2 (p90 ribosomal S6 kinase 2) is activated via the ERK (extracellular-signal-regulated kinase) pathway by phosphorylation on four sites: Ser227 in the activation loop of the N-terminal kinase domain, Ser369 in the linker, Ser386 in the hydrophobic motif and Thr577 in the C-terminal kinase domain of RSK2. In the present study, we demonstrate that RSK2 is associated in vivo with PP2Cδ (protein phosphatase 2Cδ). In epidermal growth factorstimulated cells, RSK2 is partially dephosphorylated on all four sites in an Mn2+-dependent manner, leading to reduced protein kinase activity. Furthermore, PP2Cδ is phosphorylated by ERK on Thr315 and Thr333 in the catalytic domain. Mutation of Thr315 and Thr333 to alanine in a catalytically inactive mutant PP2Cδ(H154D) (His154→Asp) increases the association with RSK2 significantly, whereas mutation to glutamate, mimicking phosphorylation, reduces the binding of RSK2. The domains of interaction are mapped to the N-terminal extension comprising residues 1–71 of PP2Cδ and the N-terminal kinase domain of RSK2. The interaction is specific, since PP2Cδ associates with RSK1–RSK4, MSK1 (mitogen- and stress-activated kinase 1) and MSK2, but not with p70 S6 kinase or phosphoinositide-dependent kinase 1. We conclude that RSK2 is associated with PP2Cδ in vivo and is partially dephosphorylated by it, leading to reduced kinase activity.

Polyomavirus middle T antigen induces ribosomal protein S6 phosphorylation through pp60c-src-dependent and -independent pathways

1988 ◽  
Vol 8 (6) ◽  
pp. 2309-2315
Author(s):  
D A Talmage ◽  
J Blenis ◽  
T L Benjamin
Keyword(s):  
Plasma Membrane ◽  
Ribosomal Protein ◽  
Kinase Activity ◽  
T Antigen ◽  
Wild Type ◽  
S6 Kinase ◽  
Ribosomal Protein S6 ◽  
Infected Cells ◽  
Polyomavirus Middle T Antigen ◽  
Middle T Antigen

Phosphorylation of ribosomal protein S6 is elevated in polyomavirus-infected cells. This elevation results only in part from activation of S6 kinase activity. These effects appear to reflect independent activities of wild-type middle T antigen. Hr-t mutant NG59, encoding a defective middle T protein, and mutant Py808A, encoding no middle T protein, were unable to induce S6 kinase activity or elevate S6 phosphorylation. Two other site-directed mutants encoding altered middle T proteins did elevate S6 phosphorylation while only weakly stimulating S6 kinase activity. These results suggest at least two independent pathways leading to elevation of S6 phosphorylation. One pathway leads to induction of S6 kinase activity following activation of pp60c-src by transformation-competent middle T antigen. Another pathway operates independently of S6 kinase induction and can be regulated by transformation-defective middle T mutants such as Py1387T. This mutant, encoding a truncated middle T protein that failed to associate with the plasma membrane and to activate pp60c-src, caused increased levels of S6 phosphorylation without detectably increasing S6 kinase activity. The ability of mutants such as Py1387T to induce S6 phosphorylation correlated with their ability to increase phosphorylation of VP1, an event linked to maturation of infectious virions.

Two distinct enzymes contribute to biphasic S6 phosphorylation in serum-stimulated chicken embryo fibroblasts

1990 ◽  
Vol 10 (6) ◽  
pp. 2787-2792
Author(s):  
L J Sweet ◽  
D A Alcorta ◽  
R L Erikson
Keyword(s):  
Chicken Embryo ◽  
Kinase Activity ◽  
Chicken Embryo Fibroblast ◽  
Total Serum ◽  
S6 Kinase ◽  
Serum Stimulation ◽  
Ribosomal Protein S6 ◽  
Phosphopeptide Analysis ◽  
Embryo Fibroblasts ◽  
Chicken Embryo Fibroblasts

Serum stimulation of quiescent chicken embryo fibroblasts resulted in a time-dependent, biphasic activation of S6 kinase activity. Chromatographic fractionation of serum-stimulated cell lysates resolved two distinct S6 kinase activities. Anti-Xenopus S6 kinase II antiserum immunoprecipitated a 90,000-Mr S6 kinase but did not cross-react with a smaller, 65,000-Mr S6 kinase. Phosphopeptide analysis confirmed that the 90,000- and 65,000-Mr proteins were structurally unrelated and established that the 65,000-Mr protein isolated by the current protocol was the same serum-stimulated chicken embryo fibroblast S6 kinase as that previously characterized (J. Blenis, C. J. Kuo, and R. L. Erikson, J. Biol. Chem. 262:14373-14376, 1987). These results demonstrate the contribution of two distinct S6 kinases to total serum-stimulated ribosomal protein S6 phosphorylation.

p42 mitogen-activated protein kinase and p90 ribosomal S6 kinase are selectively phosphorylated and activated during thrombin-induced platelet activation and aggregation

1994 ◽  
Vol 14 (1) ◽  
pp. 463-472
Author(s):  
J Papkoff ◽  
R H Chen ◽  
J Blenis ◽  
J Forsman
Keyword(s):  
Signal Transduction ◽  
Platelet Aggregation ◽  
Protein Kinase ◽  
Immune Complex ◽  
Platelet Activation ◽  
Kinase Activity ◽  
Mitogen Activated Protein Kinase ◽  
S6 Kinase ◽  
Mitogen Activated Protein ◽  
Ribosomal S6 Kinase

Human platelets provide an excellent model system for the study of phosphorylation events during signal transduction and cell adhesion. Platelets are terminally differentiated cells that exhibit rapid phosphorylation of many proteins upon agonist-induced activation and aggregation. We have sought to identify the kinases as well as the phosphorylated substrates that participate in thrombin-induced signal transduction and platelet aggregation. In this study, we have identified two forms of mitogen-activated protein kinase (MAPK), p42mapk and p44mapk, in platelets. The data demonstrate that p42mapk but not p44mapk becomes phosphorylated on serine, threonine, and tyrosine during platelet activation. Immune complex kinase assays, gel renaturation assays, and a direct assay for MAPK activity in platelet extracts all support the conclusion that p42mapk but not p44mapk shows increased kinase activity during platelet activation. The activation of p42mapk, independently of p44mapk, in platelets is unique since in other systems, both kinases are coactivated by a variety of stimuli. We also show that platelets express p90rsk, a ribosomal S6 kinase that has previously been characterized as a substrate for MAPK. p90rsk is phosphorylated on serine in resting platelets, and this phosphorylation is enhanced upon thrombin-induced platelet activation. Immune complex kinase assays demonstrate that the activity of p90rsk is markedly increased during platelet activation. Another ribosomal S6 protein kinase, p70S6K, is expressed by platelets but shows no change in kinase activity upon platelet activation with thrombin. Finally, we show that the increased phosphorylation and activity of both p42mapk and p90rsk does not require integrin-mediated platelet aggregation. Since platelets are nonproliferative cells, the signal transduction pathways that include p42mapk and p90rsk cannot lead to a mitogenic signal and instead may regulate cytoskeletal or secretory changes during platelet activation.

scholarly journals Polyomavirus middle T antigen induces ribosomal protein S6 phosphorylation through pp60c-src-dependent and -independent pathways.

1988 ◽  
Vol 8 (6) ◽  
pp. 2309-2315 ◽  
Author(s):  
D A Talmage ◽  
J Blenis ◽  
T L Benjamin
Keyword(s):  
Plasma Membrane ◽  
Ribosomal Protein ◽  
Kinase Activity ◽  
T Antigen ◽  
Wild Type ◽  
S6 Kinase ◽  
Ribosomal Protein S6 ◽  
Infected Cells ◽  
Polyomavirus Middle T Antigen ◽  
Middle T Antigen

Phosphorylation of ribosomal protein S6 is elevated in polyomavirus-infected cells. This elevation results only in part from activation of S6 kinase activity. These effects appear to reflect independent activities of wild-type middle T antigen. Hr-t mutant NG59, encoding a defective middle T protein, and mutant Py808A, encoding no middle T protein, were unable to induce S6 kinase activity or elevate S6 phosphorylation. Two other site-directed mutants encoding altered middle T proteins did elevate S6 phosphorylation while only weakly stimulating S6 kinase activity. These results suggest at least two independent pathways leading to elevation of S6 phosphorylation. One pathway leads to induction of S6 kinase activity following activation of pp60c-src by transformation-competent middle T antigen. Another pathway operates independently of S6 kinase induction and can be regulated by transformation-defective middle T mutants such as Py1387T. This mutant, encoding a truncated middle T protein that failed to associate with the plasma membrane and to activate pp60c-src, caused increased levels of S6 phosphorylation without detectably increasing S6 kinase activity. The ability of mutants such as Py1387T to induce S6 phosphorylation correlated with their ability to increase phosphorylation of VP1, an event linked to maturation of infectious virions.

Identification of mitogen-responsive ribosomal protein S6 kinase pp90rsk, a homolog of Xenopus S6 kinase II, in chicken embryo fibroblasts

1990 ◽  
Vol 10 (5) ◽  
pp. 2413-2417
Author(s):  
L J Sweet ◽  
D A Alcorta ◽  
S W Jones ◽  
E Erikson ◽  
R L Erikson
Keyword(s):  
Ribosomal Protein ◽  
Immune Complex ◽  
Chicken Embryo ◽  
Chicken Embryo Fibroblast ◽  
S6 Kinase ◽  
Ribosomal Protein S6 ◽  
Embryo Fibroblasts ◽  
Ribosomal S6 Kinase ◽  
Chicken Embryo Fibroblasts ◽  
Ribosomal Protein S6 Kinase

Antiserum raised against recombinant Xenopus ribosomal protein S6 kinase (rsk) was used to identify a 90,000-Mr ribosomal S6 kinase, pp90rsk, in chicken embryo fibroblasts. Adding serum to cells stimulated the phosphorylation of pp90rsk on serine and threonine residues and increased the activity of S6 kinase measured in immune complex assays. Xenopus S6 kinase II and chicken embryo fibroblast pp90rsk had nearly identical phosphopeptide maps.

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