Effects of hyperactive Janus kinase 2 signaling in mammary epithelial cells

Olsen, Hanne; Faulds, Malin A Hedengran; Saharinen, Pipsa; Silvennoinen, Olli; Haldosén, Lars Arne

doi:10.1016/s0006-291x(02)00847-1

Cited by 6 publications

(6 citation statements)

References 33 publications

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“…The observations of increased activity in amino-terminally deleted mutants of JAK2 are consistent with a model in which the amino-terminal domains possess autoinhibitory properties (39,40,49). The results in Figures 6 and 7 of this paper show that the N-terminal deleted GST/(N∆661)-rJAK2(YY:FF) is able to autophosphorylate at a lower ATP concentration than does the full-length GST/rJAK2(YY:FF).…”

Section: Discussionsupporting

confidence: 88%

“…It has been speculated that the amino-terminal half of JAK2 might contain autoinhibitory properties, based on the observation that amino-terminally truncated forms of JAKs appear to be “hyperactive” in comparison to full-length forms of JAKs ( , ). This raised the suspicion that the unexpected lack of demonstrable autokinase activity of GST/rJAK2(YY:FF) reflected an inability to relieve autoinhibition.…”

Section: Resultsmentioning

confidence: 99%

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Tyrosine Phosphorylation of the Janus Kinase 2 Activation Loop Is Essential for a High-Activity Catalytic State but Dispensable for a Basal Catalytic State

2004

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The phosphorylation of an "activation loop" within protein kinases is commonly associated with establishing catalytic competence, and phosphorylation of the Tyr(1007) residue in the activation loop of Janus kinase 2 (JAK2) has been shown to be essential for intracellular propagation of cytokine-initiated signaling. We provide evidence for the presence of a basal activity state of JAK2, which was observed in the absence of activation loop phosphorylation. Phosphorylation of the JAK2 activation loop was essential for conversion to the high-activity state, characterized by high-efficiency ATP utilization during autophosphorylation. Mutagenesis of activation loop tyrosine residues Tyr(1007/1008) to phenylalanine residues impaired, but did not abolish, the enzyme's ability to autophosphorylate. The activation loop mutant JAK2 could also transphosphorylate an inactive JAK2 fragment coexpressed in Sf21 cells, providing evidence of exogenous substrate phosphorylation. The mutant enzyme remained in a basal activity state characterized by low-efficiency ATP utilization during autophosphorylation. Mutagenesis of a critical Lys(882) residue to a glutamate residue abolished all evidence of kinase activity, confirming that the observed activity of Tyr-to-Phe mutants was not due to another kinase. Our data are consistent with the proposal that JAK2 is an inefficient but active enzyme in the absence of activation loop phosphorylation and is capable of conversion to a high-activity state by autophosphorylation under physiological ATP concentrations. This theoretically precludes the need for an upstream activating kinase. The activation process of JAK2 may be envisioned as a multistate process involving at least two kinetically distinct states of activity.

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Section: Discussionsupporting

confidence: 88%

Section: Resultsmentioning

confidence: 99%

Tyrosine Phosphorylation of the Janus Kinase 2 Activation Loop Is Essential for a High-Activity Catalytic State but Dispensable for a Basal Catalytic State

2004

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“…Cell cultures HeLa cells were propagated as described by Kazlauskas et al (2001). HC11 cells were grown according to Olsen et al (2002). Before transfection, the HC11 culture medium was changed to filtered RPMI without phenol red, supplemented with 5% charcoal‐treated fetal bovine serum (FBS), L ‐glutamine (2 mM), gentamycin (1%), insulin (5 μg/ml) and epidermal growth factor (10 ng/ml).…”

Section: Methodsmentioning

confidence: 99%

The co‐chaperone XAP2 is required for activation of hypothalamic thyrotropin‐releasing hormone transcription in vivo

et al. 2006

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Transcriptional control of hypothalamic thyrotropin-releasing hormone (TRH) integrates central regulation of the hypothalamohypophyseal-thyroid axis and hence thyroid hormone (triiodothyronine (T 3 )) homeostasis. The two b thyroid hormone receptors, TRb1 and TRb2, contribute to T 3 feedback on TRH, with TRb1 having a more important role in the activation of TRH transcription. How TRb1 fulfils its role in activating TRH gene transcription is unknown. By using a yeast two-hybrid screening of a mouse hypothalamic complementary DNA library, we identified a novel partner for TRb1, hepatitis virus B X-associated protein 2 (XAP2), a protein first identified as a co-chaperone protein. TR-XAP2 interactions were TR isoform specific, being observed only with TRb1, and were enhanced by T 3 both in yeast and mammalian cells. Furthermore, small inhibitory RNAmediated knockdown of XAP2 in vitro affected the stability of TRb1. In vivo, siXAP2 abrogated specifically TRb1-mediated (but not TRb2) activation of hypothalamic TRH transcription. This study provides the first in vivo demonstration of a regulatory, physiological role for XAP2.

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“…However, there is as yet no direct evidence that this is so. The murine SOCS1 binds to JAK2 (Figure 3D[26]) which has been reported to be localized to the cytoplasm [33]. Therefore, we might expect that SOCS1 may also be localized to the cytoplasm.…”

Section: Resultsmentioning

confidence: 94%

Ontological visualization of protein-protein interactions

et al. 2005

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BackgroundCellular processes require the interaction of many proteins across several cellular compartments. Determining the collective network of such interactions is an important aspect of understanding the role and regulation of individual proteins. The Gene Ontology (GO) is used by model organism databases and other bioinformatics resources to provide functional annotation of proteins. The annotation process provides a mechanism to document the binding of one protein with another. We have constructed protein interaction networks for mouse proteins utilizing the information encoded in the GO annotations. The work reported here presents a methodology for integrating and visualizing information on protein-protein interactions.ResultsGO annotation at Mouse Genome Informatics (MGI) captures 1318 curated, documented interactions. These include 129 binary interactions and 125 interaction involving three or more gene products. Three networks involve over 30 partners, the largest involving 109 proteins. Several tools are available at MGI to visualize and analyze these data.ConclusionsCurators at the MGI database annotate protein-protein interaction data from experimental reports from the literature. Integration of these data with the other types of data curated at MGI places protein binding data into the larger context of mouse biology and facilitates the generation of new biological hypotheses based on physical interactions among gene products.

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Effects of hyperactive Janus kinase 2 signaling in mammary epithelial cells

Cited by 6 publications

References 33 publications

Tyrosine Phosphorylation of the Janus Kinase 2 Activation Loop Is Essential for a High-Activity Catalytic State but Dispensable for a Basal Catalytic State

Tyrosine Phosphorylation of the Janus Kinase 2 Activation Loop Is Essential for a High-Activity Catalytic State but Dispensable for a Basal Catalytic State

The co‐chaperone XAP2 is required for activation of hypothalamic thyrotropin‐releasing hormone transcription in vivo

Ontological visualization of protein-protein interactions

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