Cadmium (Cd), a human carcinogen, can induce apoptosis in various cell types. Three major mitogen-activated protein kinases (MAPKs), c-JUN N-terminal kinase (JNK), p38 and extracellular signal-regulated kinase (ERK), have been shown to regulate apoptosis. In this study we explore the ability of Cd to activate JNK, p38 and ERK, including their effects on Cd-mediated growth inhibition and apoptosis in a human non-small cell lung carcinoma cell line, CL3. The kinase activity of JNK was induced dose-dependently by 30-160 microM CdCl(2). High cytotoxic doses of Cd (130-160 microM) markedly activated p38, but low Cd doses did not. Conversely, the activities of ERK1 and ERK2 were decreased by low cytotoxic doses of Cd (

The dual-specificity MAPK phosphatase MKP-1/CL100/DUSP1 is an inducible nuclear protein controlled by p44/42 MAPK (ERK1/2) in a negative feedback mechanism to inhibit kinase activity. Here, we report on the molecular basis for a novel positive feedback mechanism to sustain ERK activation by triggering MKP-1 proteolysis. Active ERK2 docking to the DEF motif (FXFP, residues 339 -342) of N-terminally truncated MKP-1 in vitro initiated phosphorylation at the

Sustained extracellular signal-regulated kinase 1/2 (ERK1/2) activation does not always correlate with its upstream Ras-Raf-mitogen-activated protein kinase kinase 1/2 (MKK1/2) signal cascade in cancer cells, and the mechanism remains elusive. Here we report a novel mechanism by which sustained ERK1/2 activation is established. We demonstrate that Pb(II), a carcinogenic metal, persistently induces ERK1/2 activity in CL3 human lung cancer cells and that Ras-Raf-MKK1/2 signaling cannot fully account for such activation. It is intriguing that Pb(II) treatment reduces mitogenactivated protein kinase phosphatase 1 (MKP-1) protein levels in time-and dose-dependent manners, which correlates with sustained ERK1/2 activation, and that Pb(II) also induces mRNA and de novo protein synthesis of MKP-1. In Pb ( Members of the family of mitogen-activated protein kinase (MAPK) 1 proteins are vital intracellular signaling components that become phosphorylated and activated in response to a wide diversity of extracellular stimuli, including growth factors, cytokines, and environmental stresses (reviewed in Refs. 1-5). MAPKs are activated through a three-kinase module composed of a MAPK, a MAPK kinase (MKK), and a MKK kinase (MKKK). These MAPK modules are connected to cell surface receptors and activated via interaction with a family of small GTPases and MKKK kinases. Activated MAPKs phosphorylate many substrates, including cytoskeletal proteins, other kinases, phosphatases, enzymes, and transcription factors, thereby orchestrating several cellular alterations including proliferation, differentiation, survival, and apoptosis. The duration and strength of MAPK activation also affects these biological outcomes. Three major MAPK subfamilies have been extensively studied, i.e. the extracellular signal-regulated kinases (ERK1/2), the c-Jun N-terminal kinases (JNKs), and the p38 kinases. Activation of a particular MAPK signal must be controlled with high specificity and efficiency to achieve precise physiological regulation. The recent discovery of specific docking sites among the members of the MAPK cascades provide a mechanism that explains how specific and efficient signaling is established. For instance, a cluster of positively charged amino acids followed by an LXL motif called the D domain (or the kinase interaction motif, KIM) has been identified in MKKs, MAPK phosphatases (MKPs), and several MAPK substrates (6 -8). The D domain binds specifically to an acidic domain (common docking domain) within a docking groove of MAPKs (6 -8). Another docking site found in many ERK substrates is called the DEF motif (docking site for ERK, FXFP) (8, 9). These docking interactions facilitate phosphorylation of substrates by MAPKs on specific Ser or Thr residues followed by a Pro residue ((S/T)P sites).The small GTPase, MKKK, and MKK in the ERK pathway are known to be Ras, Raf, and MKK1/2, respectively (1-5). Activation of ERK1/2 requires a dual-phosphorylation by MKK1/2 on the Thr and Tyr residues of TEY sites within the activation loop, wherea...

Metamaterials have unprecedented properties that facilitate the development of advanced devices and machines. However, their interconnected building structures limit their applications, especially in the fields that require large deformation, rich programmability and efficient shape‐reconfigurability. To break this limit and exploit more potentialities of metamaterials, an innovative material design strategy is proposed, named mechanical pixel (MP) array design. Similar to a screen that displays images by adjusting the colors of pixels, the metamaterials can form and reconfigure 3D morphologies by tuning the heights (lengths) of the MPs in the array. The strategy is demonstrated in a multistable metamaterial by experimental tests, theoretical analysis, and numerical simulations. Using this strategy, a large macroscopic shear deformation is obtained, and remarkable enhancements in the mechanical programmability, shape‐reconfigurability and adaptability, and reusable shock‐resistance are exhibited. Moreover, mechanical design and property prediction for the metamaterials are both greatly simplified due to the pixelated design. For a piece of the 3D pixel metamaterial with m n‐unit MPs, the number of programmable displacement–force curves increases from n+1 to 2m∙n+1, and the number of stable morphologies grows from n+1 to at least (n+1)m. This strategy can be used to enhance the merits and further excavate the potential of versatile metamaterials.

Kinds of mutations formed when a shuttle vector containing adducts of (±+)-7,8,8a-dihydroxy-9a,10a-epoxy-7,8,9,10- ABSTRACTWe have investigated the kinds of mutations induced when a shuttle vector containing covalently bound residues of (±)-7p,8a-dihydroxy-9a,10a-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE) replicates in human cells. A human embryonic kidney cell line, 293, was used as the eukaryotic host. The target gene for mutation analysis, supF, codes for a tyrosine suppressor tRNA and is strategically located between the origin of replication of the plasmid in Escherichia coli and the gene for a selectable marker, so that the possibility of recovering supF mutants containing gross rearrangements is low. The frequency of supF mutants obtained when untreated plasmid replicated in 293 cells was 1.