Monophosphothreonyl extracellular signal-regulated kinases 1 and 2 (ERK1/2) are formed endogenously in intact cardiac myocytes and are enzymically active

Institute for Cardiovascular and Metabolic Research, School of Biological Sciences, University of Reading, Whiteknights, Reading RG6 6UB, UK.
Cellular Signalling (Impact Factor: 4.47). 10/2010; 23(2):468-77. DOI: 10.1016/j.cellsig.2010.10.024
Source: PubMed

ABSTRACT ERK1 and ERK2 (ERK1/2) are central to the regulation of cell division, growth and survival. They are activated by phosphorylation of the Thr- and the Tyr- residues in their Thr-Glu-Tyr activation loops. The dogma is that dually-phosphorylated ERK1/2 constitute the principal activities in intact cells. We previously showed that, in neonatal rat cardiac myocytes, endothelin-1 and phorbol 12-myristate 13-acetate (PMA) powerfully and rapidly (maximal at ~5 min) activate ERK1/2. Here, we show that dually-phosphorylated ERK1/2 rapidly (< 2 min) appear in the nucleus following stimulation with endothelin-1. We characterized the active ERK1/2 species in myocytes exposed to endothelin-1 or PMA using MonoQ FPLC. Unexpectedly, two peaks of ERK1 and two peaks of ERK2 activity were resolved using in vitro kinase assays. One of each of these represented the dually-phosphorylated species. The other two represented activities for ERK1 or ERK2 which were phosphorylated solely on the Thr- residue. Monophosphothreonyl ERK1/2 represented maximally ~30% of total ERK1/2 activity after stimulation with endothelin-1 or PMA, and their k(cat) values were estimated to be minimally ~30% of the dually-phosphorylated species. Appearance of monophosphothreonyl ERK1/2 was rapid but delayed in comparison with dually-phosphorylated ERK1/2. Of 10 agonists studied, endothelin-1 and PMA were most effective in terms of ERK1/2 activation and in stimulating the appearance of monophosphothreonyl and dually-phosphorylated ERK1/2. Thus, enzymically active monophosphothreonyl ERK1/2 are formed endogenously following activation of the ERK1/2 cascade and we suggest that monophosphothreonyl ERK1/2 arise by protein tyrosine phosphatase-mediated dephosphorylation of dually-phosphorylated ERK1/2.

Download full-text


Available from: Angela Clerk, Jul 04, 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Abnormal metabolism and sustained proliferation are hallmarks of cancer. Pyruvate kinase M2 (PKM2) is a metabolic enzyme that plays important roles in both processes. Recently, PKM2 was shown to have protein kinase activity phosphorylating histone H3 and promoting cancer cell proliferation. However, the mechanism and extent of this protein kinase in cancer cells remain unclear. Here, we report that binding of succinyl-5-aminoimidazole-4-carboxamide-1-ribose-5'-phosphate (SAICAR), a metabolite abundant in proliferating cells, induces PKM2's protein kinase activity in vitro and in cells. Protein microarray experiments revealed that more than 100 human proteins, mostly protein kinases, are phosphorylated by PKM2-SAICAR. In particular, PKM2-SAICAR phosphorylates and activates Erk1/2, which in turn sensitizes PKM2 for SAICAR binding through phosphorylation. Additionally, PKM2-SAICAR was necessary to induce sustained Erk1/2 activation and mitogen-induced cell proliferation. Thus, the ligand-induced protein kinase activity from PKM2 is a mechanism that directly couples cell proliferation with intracellular metabolic status.
    Molecular cell 03/2014; 53(5):700-709. DOI:10.1016/j.molcel.2014.02.015 · 14.46 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We studied interaction of hydrophilic polymer chain and hydrophilic silica nanoparticles in a dilute aqueous system using an idealized model system comprised of a well characterized polyvinyl alcohol of 100 Å R(g) and hard spherical LUDOX® silica of 80 Å radii. Interaction among the polymer chains forming polymer clusters with collective polymer structure factor induced by the polymer-mediated potentials of mean force between the nanoparticles, was observed. However, Gaussian nature of individual polymer chain remains unaltered. The dilute system of polymer with low silica volume fraction has the scattering form which was appropriately modeled as the sum of the individual profiles of spherical silica particles and polymer cluster of interchain packing. With increasing silica volume fraction in the dilute solution, the spatial range parameter between the particles is reduced; hence there is a net increase in the mean potential force and consequently to stronger interaction between the silica and polymer. In the dilute systems of high silica with low polymer volume fraction, the polymer chain apparently attracted closer to the silica and concurrently absorbed to the silica hard surface and their scattering data were excellently fit with a model form factor as comprising of one unit forming the core of the spherical silica particles and the interacting polymer as the corona. This result of severe change in polymer interchain conformation in a dilute system corroborated with reduced polymer viscosity observed.
    Journal of Colloid and Interface Science 09/2010; 353(1):52-60. DOI:10.1016/j.jcis.2010.09.022 · 3.55 Impact Factor
  • Source
    Cellular Signalling 05/2011; 23(5):950-950. DOI:10.1016/j.cellsig.2011.01.011 · 4.47 Impact Factor