Eukaryote polyphosphate kinases: is the 'Kornberg' complex ubiquitous?

Polyphosphate (poly P) is a polymer of up to several hundred phosphate residues and is important to a variety of cell processes. The main poly P synthetic enzyme in many bacteria is poly P kinase 1 (PPK1), which until recently had been detected among eukaryotes in some protists only. There is now evidence for the presence in several other eukaryotes of PPK1 homologues and also a second bacteria-type enzyme, PPK2. The latest genome databases reveal that the 'Kornberg' enzyme complex of three actin-related proteins, termed DdPPK2 in Dictyostelium discoideum, might also be ubiquitous in eukaryotes. Owing to the intimate association of poly P synthesis with the formation of structural fibres, this ubiquity indicates a central role for this molecule in the evolution of eukaryotic cells.     

SPTBN1 and cancer,which links?

SPTBN1 is a dynamic intracellular nonpleckstrin homology-domain protein, functioning as a transforming growth factor-β signal transducing adapter protein which is necessary to form Smad3/Smad4 complex. Recently SPTBN1 is considered to be associated with many kinds of cancers. SPTBN1 expression and function differ between different tumor states or types. This review summarizes the recent advances in the expression patterns of SPTBN1 in cancers, and in understanding the mechanisms by which SPTBN1 affects the occurrence, progression, and metastasis of cancer. Identifying SPTBN1 expression and function in cancers will contribute to the clinical diagnosis and treatment of cancer and the investigation of anticancer drugs.     

Integrin adhesion: when is a kinase a kinase?

Recent genetic studies in the worm Caenorhabditis elegans and fruitfly Drosophila have revealed the essential role integrin-linked kinase plays in integrin adhesion - but it apparently acts in this role as an adaptor rather than a kinase.     

p34cdc2: the S and M kinase?

In the yeast cell cycle, the induction of two very different processes, DNA synthesis (S-phase) and mitosis (M-phase), requires the same serine/threonine-specific protein kinase p34cdc2, which has been highly conserved through evolution. On the basis of work conducted largely in multicellular eukaryotes, it has recently been suggested that p34cdc2 is able to perform these two mutually exclusive roles by phosphorylating different sets of substrates through a cell cycle-dependent association with other proteins that dictate the substrate specificity of the protein kinase. To recognize its mitotic substrates, p34cdc2 associates with one of the cyclins--a family of proteins of two distinct but related types (A and B) characterized by their periodic destruction at each mitosis. In interphase, the formation of a complex between p34cdc2 and another protein (or proteins) would allow the phosphorylation of a different set of proteins involved in the G1 to S transition. This review focuses on the evidence for this appealing simple model and the nature of the putative substrates proposed.     

Flooding or drought which one is more offensive on pepper physiology and growth?

Molecular Biology Reports - Both extreme usage of water in agriculture i.e., drought and flooding affect physiological and growth aspects of the plant as well as gene expression undertaken in water...     

Estuarine and mangrove systems and the nursery concept: which is which? The case of the Sine Saloum system (Senegal)

The mangrove system of Sine Saloum in Senegal is characterized by the lack of permanent river flow, in the context of the Sahelian drought which began in the 70s. The main environmental consequence is that Sine Saloum has become a so called reversed estuary with salinity increasing upstream and reaching 100 and more, with a mean salinity between 45–50. A threeyear survey of the juvenile fish community was undertaken with the aim of verifying whether or not this environment is still suitable as a nursery area for exploited fish populations. The main sampling gear used were small fykenets in addition to gill nets and a limited rotenone sampling. One of the six mangrove stations included in the survey exhibited a relatively high species diversity. This station is the only one where salinity may reach levels as low as 25 at the end of the rainy season, although salinity is much higher in the upstream region near this station. Such a low salinity is likely due to an underground freshwater connection or underwater springs. These observations highlight the relative importance of estuaries and mangroves in the nursery function.     

Phospholipase C and protein kinase C-β 2 mediate insulin-like growth factor II-dependent sphingosine kinase 1 activation

We recently reported that IGF-II binding to the IGF-II/mannose-6-phosphate (M6P) receptor activates the ERK1/2 cascade by triggering sphingosine kinase 1 (SK1)-dependent transactivation of G protein-coupled sphingosine 1-phosphate (S1P) receptors. Here, we investigated the mechanism of IGF-II/M6P receptor-dependent sphingosine kinase 1 (SK1) activation in human embryonic kidney 293 cells. Pretreating cells with protein kinase C (PKC) inhibitor, bisindolylmaleimide-I, abolished IGF-II-stimulated translocation of green fluorescent protein (GFP)-tagged SK1 to the plasma membrane and activation of endogenous SK1, implicating PKC as an upstream regulator of SK1. Using confocal microscopy to examine membrane translocation of GFP-tagged PKCα, β1, β2, δ, and ζ, we found that IGF-II induced rapid, transient, and isoform-specific translocation of GFP-PKCβ2 to the plasma membrane. Immunoblotting of endogenous PKC phosphorylation confirmed PKCβ2 activation in response to IGF-II. Similarly, IGF-II stimulation caused persistent membrane translocation of the kinase-deficient GFP-PKCβ2 (K371R) mutant, which does not dissociate from the membrane after translocation. IGF-II stimulation increased diacylglycerol (DAG) levels, the established activator of classical PKC. Interestingly, the polyunsaturated fraction of DAG was increased, indicating involvement of phosphatidyl inositol/phospholipase C (PLC). Pretreating cells with the PLC inhibitor, U73122, attenuated IGF-II-dependent DAG production and PKCβ2 phosphorylation, blocked membrane translocation of the kinase-deficient GFP-PKCβ2 (K371R) mutant, and reduced sphingosine 1-phosphate production, suggesting that PLC/PKCβ2 are upstream regulators of SK1 in the pathway. Taken together, these data provide evidence that activation of PLC and PKCβ2 by the IGF-II/M6P receptor are required for the activation of SK1.     

A cotton mitogen-activated protein kinase （GhMPK6） is involved in ABA-induced CAT1 expression and H2O2 production

The mitogen-activated protein kinase (MAPK) cascade is one of the major and evolutionally conserved signaling pathways and plays a pivotal role in the regulation of stress and developmental signals in plants.Here,we identified one gene,GhMPK6,encoding an MAPK protein in cotton.GFP fluorescence assay demonstrated that GhMAPK6 is a cytoplasm localized protein.Quantitative RT-PCR analysis revealed that mRNA accumulation of GhMPK6 was significantly promoted by abscisic acid (ABA).Overexpression of GhMPK6 gene in the T-DNA insertion mutant atmkkl (SALK_015914) conferred a wild-type phenotype to the transgenic plants in response to ABA.Under ABA treatment,cotyledon greening/expansion in GhMPK6 transgenic lines and wild type was significantly inhibited,whereas the atmkkl mutant showed a relatively high cotyledon greening/expansion ratio.Furthermore,CAT1 expression and H2O2 levels in leaves of GhMPK6 transgenic lines and wild type were remarkably higher than those of atmkkl mutant with ABA treatment.Collectively,our results suggested that GhMPK6 may play an important role in ABA-induced CAT1 expression and H2O2 production.     

Coexistence of competing parasitoids: which is the fugitive and where does it hide?

Most insects harbour a community of parasitoids that coexist in spite of competition for resources. One potential mechanism for coexistence of competitors is a tradeoff between dispersiveness and local competitive ability. Here we present a study of competition between the specialized parasitoids Hyposoter horticola and Cotesia melitaearum sharing the Glanville fritillary butterfly, Melitaea cinxia . Within one host generation, the parasitoid larvae interact inside the host during each of the three C. melitaearum generations. We founds that in the summer when the host is small, the solitary H. horticola is the superior competitor, suppressing the gregarious C. melitaearum as eggs or small larvae. When multiparasitism occurs in the autumn the two parasitoid species engage in physical combat and C. melitaearum is favoured. Finally, a previous study showed that in the third C. melitaearum generation the univoltine H. horticola grows quickly during its final instar, excluding young C. melitaearum simply through limited time and resources. We found that contrary to expectations of the evolution of gregariousness, C. melitaearum , which lives in sibling groups, has biting mandibles in the first instar while the solitary H. horticola has suctorial mouthparts. Previous studies suggest that the two parasitoids co-exist because H. Horticola is dispersive and C. melitaearum is a strong local competitor. However, putting together the results of this experiment and out recent understanding of the adult wasp foraging behaviours and large scale population dynamics, we conclude that H. horticola is both a superior local competitor and more dispersive than C. melitaearum . Cotesia melitaearum has no impact on the population dynamics of H. horticola , persisting as a fugitive using a small fraction the larvae left unparasitized by H. horticola .     

Linear dichroism of biomolecules: which way is up?

Understanding the organization of molecules in naturally occurring ordered arrays (e.g. membranes, protein fibres and DNA strands) is of great importance to understanding biological function. Unfortunately, few biophysical techniques provide detailed structural information on these non-crystalline systems. UV, visible and IR linear dichroism have the potential to provide such information. Recent advances in technology and simulations allow this potential to be fulfilled, and can now provide a detailed understanding of the molecular mechanisms of such fundamental biological processes as amyloid fibre formation and membrane protein folding.     

Apoptosis signal-regulating kinase1 is inducible by protein kinase Cδ and contributes to phorbol ester-mediated G1 phase arrest through persistent JNK activation

Although protein kinase Cδ (PKCδ) has been suggested in the negative control of the cell cycle machinery in many types of cancer cells, its underlying mechanisms are partly understood. Here we report that the expression of apoptosis signal-regulating kinase1 (ASK1) is inducible in a PKCδ-dependent manner, and contributes to phorbol ester-induced cell cycle arrest through persistent JNK activation in breast cancer epithelial cells. Activation of PKC with phorbol 12-myristate 13-acetate (PMA) gradually up-regulated the expression of ASK1 mRNA and protein, and subsequently enhanced its catalytic activity in MCF-7 cells. Importantly, such PMA-induced ASK1 expression was completely abolished by pretreatment of rottlerin, a specific PKCδ inhibitor or by knocking down the expression of PKCδ, while ectopic expression of a constitutively active form of PKCδ strongly up-regulated ASK1 expression. We also found that the persistent activation of mitogen-activated protein kinase, JNK in response to PMA was greatly attenuated by RNA interference-mediated knockdown of ASK1. Taken together, these results suggest that inducible expression of ASK1 by PKCδ contributes to the G1 arrest by enhancing persistent JNK signaling activation which represents a novel alternative mechanism of PKCδ-dependent cell cycle arrest and limiting proliferation of breast cancer epithelial cells.