AMP-activated protein kinase and metabolic regulation in cold-hardy insects.

Winter survival for many insects depends on cold hardiness adaptations as well as entry into a hypometabolic diapause state that minimizes energy expenditure. We investigated whether AMP-activated protein kinase (AMPK) could be involved in this adaptation in larvae of two cold-hardy insects, Eurosta solidaginis that is freeze tolerant and Epiblema scudderiana that uses a freeze avoidance strategy. AMPK activity was almost 2-fold higher in winter larvae (February) compared with animals collected in September.

Polyomavirus middle T-antigen is a transmembrane protein that binds signaling proteins in discrete subcellular membrane sites.

Murine polyomavirus middle T-antigen (MT) induces tumors by mimicking an activated growth factor receptor. An essential component of this action is a 22-amino-acid hydrophobic region close to the C terminus which locates MT to cell membranes. Here, we demonstrate that this sequence is a transmembrane domain (TMD) by showing that a hemagglutinin (HA) tag added to the MT C terminus is exposed on the outside of the cells, with the N terminus inside.

Phosphorylation of translation factors in response to anoxia in turtles, Trachemys scripta elegans: role of the AMP-activated protein kinase and target of rapamycin signalling pathways.

Long-term survival of oxygen deprivation by animals with well-developed anoxia tolerance depends on multiple biochemical adaptations including strong metabolic rate depression. We investigated whether the AMP-activated protein kinase (AMPK) could play a regulatory role in the suppression of protein synthesis that occurs when turtles experience anoxic conditions. AMPK activity and the phosphorylation state of ribosomal translation factors were measured in liver, heart, red muscle and white muscle of red-eared slider turtles (Trachemys scripta elegans) subjected to 20 h of anoxic submergence.

Polyoma virus and simian virus 40 as cancer models: history and perspectives.

Polyoma virus and SV40 are the founding members of the Polyomaviridae. They are small viruses, with a genome consisting of around 5.3kbases of closed circular, double-stranded DNA.

A functional interaction between RIP140 and PGC-1alpha regulates the expression of the lipid droplet protein CIDEA.

Nuclear receptors activate or repress target genes depending on the recruitment of coactivators or corepressors. The corepressor RIP140 and the PPAR coactivator 1alpha (PGC-1alpha) both play key roles in the regulated transcription of genes involved in energy homeostasis. We investigated the roles of RIP140 and PGC-1alpha in controlling the expression of CIDEA, an important regulatory factor in adipose cell function and obesity.

RIP140 directs histone and DNA methylation to silence Ucp1 expression in white adipocytes.

Nuclear receptors control the function of cells by regulating transcription from specific gene networks. The establishment and maintenance of epigenetic gene marks is fundamental to the regulation of gene transcription and the control of cell function. RIP140 is a corepressor for nuclear receptors that suppresses transcription from a broad programme of metabolic genes and thereby controls energy homoeostasis in vivo.

Rapid activation of ATM on DNA flanking double-strand breaks.

The tumour-suppressor gene ATM, mutations in which cause the human genetic disease ataxia telangiectasia (A-T), encodes a key protein kinase that controls the cellular response to DNA double-strand breaks (DSBs). DNA DSBs caused by ionizing radiation or chemicals result in rapid ATM autophosphorylation, leading to checkpoint activation and phosphorylation of substrates that regulate cell-cycle progression, DNA repair, transcription and cell death. However, the precise mechanism by which damaged DNA induces ATM and checkpoint activation remains unclear.

Abnormal preantral folliculogenesis in polycystic ovaries is associated with increased granulosa cell division.

Context: Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in women, but its etiology remains obscure. Recent data suggest that an intrinsic abnormality of early follicle development in the ovary is key to the pathogenesis of PCOS. We have recently found that in PCOS the proportion of primordial follicles is decreased with a reciprocal increase in the proportion of primary follicles.

Stress-induced activation of the AMP-activated protein kinase in the freeze-tolerant frog Rana sylvatica.

Survival in the frozen state depends on biochemical adaptations that deal with multiple stresses on cells including long-term ischaemia and tissue dehydration. We investigated whether the AMP-activated protein kinase (AMPK) could play a regulatory role in the metabolic re-sculpting that occurs during freezing. AMPK activity and the phosphorylation state of translation factors were measured in liver and skeletal muscle of wood frogs (Rana sylvatica) subjected to anoxia, dehydration, freezing, and thawing after freezing.

Evaluation of the role of AMP-activated protein kinase and its downstream targets in mammalian hibernation.

Mammalian hibernation requires an extensive reorganization of metabolism that typically includes a greater than 95% reduction in metabolic rate, selective inhibition of many ATP-consuming metabolic activities and a change in fuel use to a primary dependence on the oxidation of lipid reserves. We investigated whether the AMP-activated protein kinase (AMPK) could play a regulatory role in this reorganization. AMPK activity and the phosphorylation state of multiple downstream targets were assessed in five organs of thirteen-lined ground squirrels (Spermophilus tridecemlineatus) comparing euthermic animals with squirrels in deep torpor.

Activation of the protein kinase B pathway by the HPV-16 E7 oncoprotein occurs through a mechanism involving interaction with PP2A.

Protein kinase B (PKB) or Akt is one of several second messenger kinases that are activated by cell attachment and growth factor signaling, and that transmit signals to the cell nucleus to inhibit apoptosis and thereby increase cell survival during proliferation. Other viral proteins target this pathway by increasing PKB/Akt phosphorylation, and this pathway has been implicated in the transformation of human keratinocytes by HPV E6 and E7, together with activated notch 1. Here, we examine how HPV E7 expression affects the phosphorylation of PKB.

Switching on kinases: oncogenic activation of BRAF and the PDGFR family.

The cytoplasmic serine/threonine kinase BRAF and receptor tyrosine kinases of the platelet-derived growth factor receptor (PDGFR) family are frequently activated in cancer by mutations of an equivalent amino acid. Structural studies have provided important insights into why these very different kinases share similar oncogenic hot spots and why the PDGFR juxtamembrane region is also a frequent oncogenic target. This research has implications for other kinases that are mutated in human tumours and for the treatment of cancer using kinase inhibitors.

Polyoma virus middle T antigen and its role in identifying cancer-related molecules.

Most cancer researchers take for granted some of the basic concepts about the molecular changes that underlie tumorigenesis. These include the principles that tyrosine kinases and the phosphorylation of phosphatidylinositol by phosphatidylinositol 3-kinases are important in the signalling pathways that control proliferation and apoptosis, and hence cancer formation. However, how many know that a small DNA mouse virus was crucial in establishing both of these tenets?

Diagnosis of genito-urinary tract cancer by detection of minichromosome maintenance 5 protein in urine sediments.

Background: Because cystoscopy is invasive and expensive and urine cytology has low sensitivity, alternative methods for detecting bladder cancer are sought. Minichromosome maintenance (Mcm) proteins have been used as diagnostic markers for cervical cancer. We investigated whether one Mcm protein, Mcm5, can be used to detect urothelial cancer cells in urine sediments.

Dephosphorylation of PKCdelta by protein phosphatase 2Ac and its inhibition by nucleotides.

The protein phosphatases PP1(c), PP2A(c) and PP2Calpha are shown to dephosphorylate protein kinase Cdelta (PKCdelta) in vitro; of these PP2A(c) displayed the highest specific activity towards PKCdelta. The role of PP2A(c) in the dephosphorylation of PKCdelta in cells was supported by the demonstration that these proteins could be co-immunoprecipitated from NIH3T3 cells. However the observation that binding of Mg-ATP to PKCdelta could protect the enzyme from dephosphorylation by PP2A(c) in vitro indicates that an additional input/factor is required for dephosphorylation in vivo.