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TNF-induced MAP kinase activation oscillates in time.

ABSTRACT: Oscillations in the activation of multiple signaling pathways have never been shown before. Our results presented in the previous accompanying paper showed that TNF induces highly dynamic oscillations in mRNA production in approximately 13% of the mouse genome. Here, we further analyze the TNF time-series microarray data and find that multiple signaling components downstream of the TNF receptor undergo oscillations. Prior studies implicate IkappaBalpha and A-20 as the only oscillatory components in the TNF signaling cascade. We find however, that other components, such as TRAF1, displayed oscillations. This suggested the possibility that all signaling output from the TNF receptor may be oscillatory in nature. Indeed, we show that TNF triggers oscillations in the phosphorylation of three MAP kinases, as well as p65. Because Baltimore and colleagues had proposed that NF-kappaB drives the oscillatory nature of the IkappaBalpha/NF-kappaB feedback loop, we studied the effects of an NF-kappaB super-repressor on oscillations in MAPK phosphorylation; we find that the super-repressor altered the amplitude and frequency of MAP kinase phosphorylation, but failed to abolish oscillations. These results attest to a role for NF-kappaB as a modulator, but not the sole determinant of cyclical activation of signal transduction pathways. These results, together with those of the two accompanying papers, constitute a new paradigm through which cells orchestrate signaling molecules to produce highly dynamic physiological processes such as gene transcription and protein secretion. In view of the discovery that multiple phosphorylation pathways display dynamic oscillations, time-resolved, instead of static, measurements of kinase phosphorylation should become the experimental norm.

SUBMITTER: Iqbal J

PROVIDER: S-EPMC2696359 | biostudies-literature | 2008 Jul

REPOSITORIES: biostudies-literature

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TNF-induced MAP kinase activation oscillates in time.

Iqbal Jameel J Zaidi Mone M

Biochemical and biophysical research communications 20080331 4

Oscillations in the activation of multiple signaling pathways have never been shown before. Our results presented in the previous accompanying paper showed that TNF induces highly dynamic oscillations in mRNA production in approximately 13% of the mouse genome. Here, we further analyze the TNF time-series microarray data and find that multiple signaling components downstream of the TNF receptor undergo oscillations. Prior studies implicate IkappaBalpha and A-20 as the only oscillatory components ...[more]

PMID: 18384751

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Project description:Hydrogen-deuterium exchange measurements represent a powerful approach to investigating changes in conformation and conformational mobility in proteins. Here, we examine p38alpha MAP kinase (MAPK) by hydrogen-exchange (HX) mass spectrometry to determine whether changes in conformational mobility may be induced by kinase phosphorylation and activation. Factors influencing sequence coverage in the HX mass spectrometry experiment, which show that varying sampling depths, instruments, and peptide search strategies yield the highest coverage of exchangeable amides, are examined. Patterns of regional deuteration in p38alpha are consistent with tertiary structure and similar to deuteration patterns previously determined for extracellular-signal-regulated kinase (ERK) 2, indicating that MAPKs are conserved with respect to the extent of local amide HX. Activation of p38alpha alters HX in five regions, which are interpreted by comparing X-ray structures of unphosphorylated p38alpha and X-ray structures of phosphorylated p38gamma. Conformational differences account for altered HX within the activation lip, the P+1 site, and the active site. In contrast, HX alterations are ascribed to activation-induced effects on conformational mobility, within substrate-docking sites (alphaF-alphaG, beta7-beta8), the C-terminal core (alphaE), and the N-terminal core region (beta4-beta5, alphaL16, alphaC). Activation also decreases HX in a 3-10 helix at the C-terminal extension of p38alpha. Although this helix in ERK2 forms a dimerization interface that becomes protected from HX upon activation, analytical ultracentrifugation shows that this does not occur in p38alpha because both unphosphorylated and diphosphorylated forms are monomeric. Finally, HX patterns in monophosphorylated p38alpha are similar to those in unphosphorylated kinase, indicating that the major activation lip remodeling events occur only after diphosphorylation. Importantly, patterns of activation-induced HX show differences between p38alpha and ERK2 despite their similarities in overall deuteration, suggesting that although MAPKs are closely related with respect to primary sequence and tertiary structure, they have distinct mechanisms for dynamic control of enzyme function.

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TNF-induced MAP kinase activation oscillates in time.

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TNF-induced MAP kinase activation oscillates in time.

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