Identification of phosphorylation sites on human deoxycytidine kinase after overexpression in eucaryotic cells

Compelling evidence suggests that deoxycytidine kinase (dCK), a key enzyme in the salvage of deoxyribonucleosides and in the activation of clinically relevant nucleoside analogues, can be regulated by reversible phosphorylation. In this study, we show that dCK overexpressed in HEK-293T cells was labelled after incubation of the cells with [32P]orthophosphate. Tandem mass spectrometry allowed the identification of 4 in vivo phosphorylation sites, Thr3, Ser11, Ser15, and Ser74. These results provide the first evidence that dCK is constitutively multiphosphorylated in intact cells. In addition, site-directed mutagenesis demonstrated that phosphorylation of Ser74, the major in vivo phosphorylation site, is crucial for dCK activity.

New evidences for a regulation of deoxycytidine kinase activity by reversible phosphorylation

Recent studies indicate that deoxycytidine kinase (dCK), which activates various nucleoside analogues used in antileukemic therapy, can be regulated by post-translational modification, most probably through reversible phosphorylation. To further unravel its regulation, dCK was overexpressed in HEK-293 cells as a His-tag fusion protein. Western blot analysis showed that purified overexpressed dCK appears as doublet protein bands. The slower band disappeared after treatment with protein phosphatase lambda (PP lambda) in parallel with a decrease of dCK activity, providing additional arguments in favor of both phosphorylated and unphosphorylated forms of dCK.

Microbeam synchrotron imaging of hairs from ancient Egyptian mummies

Developments in microfocus synchrotron techniques have led to new results regarding the long-term alteration of archaeological samples of biological origin. Here, ancient hair samples from two Egyptian mummies have been analyzed using a conjunction of structural and elemental synchrotron methods. In this favored context of conservation, structural analysis revealed a remarkable preservation of keratin supramolecular organization at any observed length scale. Bulk keratin structure has therefore not been modified significantly over 2000 years. However, infrared spectroscopy indicated a partial disorganization of keratins close to the hair surface through polypeptide bond breakage. Elemental mapping showed a strongly heterogeneous distribution which can be related to mummification and cosmetic treatments.

Lead-revealed lipid organization in human hair

Human hair lipids form a complex mixture of composition close to that of sebum. Part of these lipids appears in an organized state that has been studied by diffraction techniques in the literature. Nevertheless, information on the structure of these lipids remains very scarce due to their low contribution to global hair diffraction pattern. Here we show that appropriate lead treatment considerably enhances organized lipid features observed by microbeam synchrotron radiation diffraction experiments. We attribute these features to the formation of lead soaps of free fatty acids. Specific orientation of hair "lipid crystals" in planes parallel to the hair axis is clearly demonstrated. Inclusion of these lipids in the bulk of the hair shaft is shown by diffraction experiments following removal of the cuticular outermost layer of hair. Moreover, microfluorescence and diffraction experiments are consistent with part of the lipids being present as calcium soaps in native hair. We therefore consider lead fixation as a powerful tool to evaluate the lipid organization in human hair for medical, environmental and archaeological purposes, including lead poisoning.

New targets of AMP-activated protein kinase

The discovery of the AMP-activated protein kinase (AMPK) more than a decade ago has shed much light on the cellular response to stresses characterized by a fall in the concentration of ATP and an increase in the AMP/ATP ratio. All conditions known to increase this ratio activate AMPK, whose major role is to act as an emergency signal to conserve ATP. It does so by inhibiting anabolic processes and by activating pathways producing ATP. In recent years, our laboratory has discovered new targets of AMPK. The purpose of this short review is to summarize our contribution to this field.

Construction and analysis of a microsatellite-based database of European wheat varieties

A database of 502 recent European wheat varieties, mainly of winter type, was constructed using 19 wheat microsatellites and one secalin-specific marker. All datapoints were generated in at least two laboratories using different techniques for fragment analysis. An overall level of >99.5% accuracy was achieved. The 199 alleles detected allowed discrimination between all of the varieties except duplicates, and varieties derived from identical parents. Approximately 25% of the varieties showed some heterogeneities, with the highest level of heterogeneity in south-eastern European material. The highest genetic diversity and the highest number of rare alleles were found in varieties from southern Europe. The relative allele frequencies varied for most microsatellites in different geographical regions.

Thyroid hormone distribution in the mouse brain: the role of transthyretin

Transthyretin is the major thyroxine-binding protein in the plasma of rodents, and the main thyroxine-binding protein in the cerebrospinal fluid of both rodents and humans. The choroid plexus synthesizes transthyretin and secretes it to the cerebrospinal fluid. Although it was suggested that transthyretin might play an important role in mediating thyroxine transfer from the blood into the brain across the choroid plexus-cerebrospinal fluid barrier, newer findings question this hypothesis. Because thyroid hormone passage across brain barriers is a precondition for its action in the CNS, and because brain is an important target of thyroid hormone action, we investigated the role of transthyretin in mediating thyroid hormone access to and distribution within the brain in a transthyretin-null mouse model system. In this report we describe the results derived from use of film autoradiography, a technique that yields definitive morphological results. Film autoradiograms were prepared at 3 and 19 h after intravenous injection of either high specific activity [(125)I]thyroxine or [(125)I]triiodothyronine. Image analyses were designed to demonstrate regional changes in hormone distribution, and to highlight alterations in iodothyronine delivery from ventricles to brain parenchyma. We find no qualitative or quantitative differences in these parameters between the transthyretin-null and the wild-type mouse brain after either [(125)I]thyroxine or [(125)I]triiodothyronine administration. The data presented here now provide definitive evidence that, under standard laboratory conditions, transthyretin is not required for thyroid hormone access to or distribution within the mouse brain. This study also provides the first map of iodothyronine distribution in the brain of the mouse.

Construction and testing of a microsatellite database containing more than 500 tomato varieties

The aim of this study was to evaluate the suitability of sequence tagged microsatellite site (STMS) markers for varietal identification and discrimination in tomato. For this purpose, a set of 20 STMS primer pairs was used to construct a database containing the molecular description of the most common varieties (>500) of tomato grown in Europe. The database was built and tested by a consortium of five European laboratories each using a different STMS detection system. In this way, it could be demonstrated that the STMS markers and database were suitable for use in network activities where a common database is being established on a continuing basis with data from different laboratories.Microsatellite polymorphism in tomato was found to be relatively low. The number of alleles per locus ranged from 2 to 8 with an average of 4.7 alleles per locus. Nevertheless, more than 90% of the varieties had different microsatellite profiles. A "blind testing" exercise showed that in general, identification of unknown samples (or detecting the most similar variety) with the 20 markers and the database was relatively easy for homogeneous varieties but less certain with heterogeneous varieties when using pools of 6 individuals.

Insulin antagonizes AMP-activated protein kinase activation by ischemia or anoxia in rat hearts, without affecting total adenine nucleotides

AMP-activated protein kinase (AMPK) is known to be activated by phosphorylation on Thr172 in response to an increased AMP/ATP ratio. We report here that such an activation indeed occurred in anaerobic rat hearts and that it was antagonized (40-50%) when the hearts were pre-treated with 100 nM insulin. The effect of insulin (1) was blocked by wortmannin, an inhibitor of phosphatidylinositol-3-kinase; (2) only occurred when insulin was added before anoxia, suggesting a hierarchical control; (3) resulted in a decreased phosphorylation state of Thr172 in AMPK and (4) was unrelated to changes in the AMP/ATP ratio. This is the first demonstration that AMPK activity could be changed without a detectable change in the AMP/ATP ratio of the cardiac cell.

No-flow ischemia inhibits insulin signaling in heart by decreasing intracellular pH

Glucose-insulin-potassium solutions exert beneficial effects on the ischemic heart by reducing infarct size and mortality and improving postischemic left ventricular function. Insulin could be the critical protective component of this mixture, although the insulin response of the ischemic and postischemic myocardium has not been systematically investigated. The aim of this work was to study the insulin response during ischemia by analyzing insulin signaling. This was evaluated by measuring changes in activity and/or phosphorylation state of insulin signaling elements in isolated perfused rat hearts submitted to no-flow ischemia. Intracellular pH (pH(i)) was measured by NMR. No-flow ischemia antagonized insulin signaling including insulin receptor, insulin receptor substrate-1, phosphatidylinositol 3-kinase, protein kinase B, p70 ribosomal S6 kinase, and glycogen synthase kinase-3. These changes were concomitant with intracellular acidosis. Perfusing hearts with ouabain and amiloride in normoxic conditions decreased pH(i) and insulin signaling, whereas perfusing at pH 8.2 counteracted the drop in pH(i) and the inhibition of insulin signaling by ischemia. Incubation of cardiomyocytes in normoxic conditions, but at pH values below 6.75, mimicked the effect of ischemia and also inhibited insulin-stimulated glucose uptake. Finally, the in vitro insulin receptor tyrosine kinase activity was progressively inhibited at pH values below physiological pH(i), being abolished at pH 6.0. Therefore, ischemic acidosis decreases kinase activity and tyrosine phosphorylation of the insulin receptor thereby preventing activation of the downstream components of the signaling pathway. We conclude that severe ischemia inhibits insulin signaling by decreasing pH(i).

Phosphorylation and activation of heart PFK-2 by AMPK has a role in the stimulation of glycolysis during ischaemia

BACKGROUND

The role of protein phosphorylation in the Pasteur effect--the phenomenon whereby anaerobic conditions stimulate glycolysis--has not been addressed. The AMP-activated protein kinase (AMPK) is activated when the oxygen supply is restricted. AMPK acts as an energy-state sensor and inhibits key biosynthetic pathways, thus conserving ATP. Here, we studied whether AMPK is involved in the Pasteur effect in the heart by phosphorylating and activating 6-phosphofructo-2-kinase (PFK-2), the enzyme responsible for the synthesis of fructose 2,6-bisphosphate, a potent stimulator of glycolysis.

RESULTS

Heart PFK-2 was phosphorylated on Ser466 and activated by AMPK in vitro. In perfused rat hearts, anaerobic conditions or inhibitors of oxidative phosphorylation (oligomycin and antimycin) induced AMPK activation, which correlated with PFK-2 activation and with an increase in fructose 2,6-bisphosphate concentration. Moreover, in cultured cells transfected with heart PFK-2, oligomycin treatment resulted in a parallel activation of endogenous AMPK and PFK-2. In these cells, the activation of PFK-2 was due to the phosphorylation of Ser466. A dominant-negative construct of AMPK abolished the activation of endogenous and cotransfected AMPK, and prevented both the activation and phosphorylation of transfected PFK-2 by oligomycin.

CONCLUSIONS

AMPK phosphorylates and activates heart PFK-2 in vitro and in intact cells. AMPK-mediated PFK-2 activation is likely to be involved in the stimulation of heart glycolysis during ischaemia.

The HeartSmart Family Fun Pack: an evaluation of family-based intervention for cardiovascular risk reduction in children

In 1998, the Heart and Stroke Foundation launched the HeartSmart Family Fun Pack, a "user-friendly" resource to support family-based lifestyle changes among children age 6-12 years. Of 1,387 parents who completed a pre-intervention questionnaire, 300 (21%) were surveyed three months later. Comparisons of the pre- and post-intervention surveys show that the Family Fun Pack was effective in supporting healthy lifestyle changes (38% and 28% of families reported improvement in their child's nutrition and level of physical activity, respectively; 12% reported reduced passive smoking). Effectiveness was greatest among those families who self-identified themselves as being in what corresponds to the contemplation, preparation and action stages of change. This evaluation suggests that a relatively low-cost intervention can be effective in supporting positive lifestyle changes if targeted to families at specific points in the stages of change.

The HeartSmart Family Fun Pack: an evaluation of family-based intervention for cardiovascular risk reduction in children

In 1998, the Heart and Stroke Foundation launched the HeartSmart Family Fun Pack, a "user-friendly" resource to support family-based lifestyle changes among children age 6-12 years. Of 1,387 parents who completed a pre-intervention questionnaire, 300 (21%) were surveyed three months later. Comparisons of the pre- and post-intervention surveys show that the Family Fun Pack was effective in supporting healthy lifestyle changes (38% and 28% of families reported improvement in their child's nutrition and level of physical activity, respectively; 12% reported reduced passive smoking). Effectiveness was greatest among those families who self-identified themselves as being in what corresponds to the contemplation, preparation and action stages of change. This evaluation suggests that a relatively low-cost intervention can be effective in supporting positive lifestyle changes if targeted to families at specific points in the stages of change.

Partial purification and characterization of a wortmannin-sensitive and insulin-stimulated protein kinase that activates heart 6-phosphofructo-2-kinase

A wortmannin-sensitive and insulin-stimulated protein kinase (WISK), which phosphorylates and activates cardiac 6-phosphofructo-2-kinase (PFK-2), was partially purified from perfused rat hearts. Immunoblotting showed that WISK was devoid of protein kinase B (PKB), serum- and glucocorticoid-regulated protein kinase and protein kinase Czeta (PKCzeta). Comparison of the inhibition of WISK, PKCalpha and PKCzeta by different protein kinase inhibitors suggested that WISK was not a member of the PKC family. In addition, WISK contained no detectable phosphoinositide-dependent protein kinase-1 (PDK1) activity. WISK phosphorylated recombinant heart PFK-2 in a time-dependent manner to the extent of 0.4 mol of phosphate incorporated/mol of enzyme subunit, and increased the V(max) of PFK-2 twofold, without affecting the K(m) for fructose 6-phosphate. WISK phosphorylated Ser-466 to a greater extent than Ser-483 in recombinant heart PFK-2, and both sites were demonstrated to be phosphorylated to the same extent by PKB. Gel filtration and in-gel kinase analysis indicated that WISK was a monomer with a M(r) of 56500. Treatment of WISK with protein phosphatase 2A (PP2A) catalytic subunits reversed the effect of insulin, suggesting the involvement of an upstream activating kinase. Indeed, PDK1 was able to partially reactivate the PP2A-treated WISK and this reactivation was not enhanced by PtdIns(3,4,5)P(3)-containing vesicles. Moreover, a single 57000-M(r) band was labelled on incubation of the dephosphorylated WISK preparation with PDK1 and [gamma-(32)P]ATP. These findings provide evidence for the existence of a new protein kinase in the insulin signalling pathway, probably downstream of PDK1.

Heart 6-phosphofructo-2-kinase activation by insulin results from Ser-466 and Ser-483 phosphorylation and requires 3-phosphoinositide-dependent kinase-1, but not protein kinase B

Previous studies have shown that (i) the insulin-induced activation of heart 6-phosphofructo-2-kinase (PFK-2) is wortmannin-sensitive, but is insensitive to rapamycin, suggesting the involvement of phosphatidylinositol 3-kinase; and (ii) protein kinase B (PKB) activates PFK-2 in vitro by phosphorylating Ser-466 and Ser-483. In this work, we have studied the effects of phosphorylation of these residues on PFK-2 activity by replacing each or both residues with glutamate. Mutation of Ser-466 increased the V(max) of PFK-2, whereas mutation of Ser-483 decreased citrate inhibition. Mutation of both residues was required to decrease the K(m) for fructose 6-phosphate. We also studied the insulin-induced activation of heart PFK-2 in transfection experiments performed in human embryonic kidney 293 cells. Insulin activated transfected PFK-2 by phosphorylating Ser-466 and Ser-483. Kinase-dead (KD) PKB and KD 3-phosphoinositide-dependent kinase-1 (PDK-1) cotransfectants acted as dominant negatives because both prevented the insulin-induced activation of PKB as well as the inactivation of glycogen-synthase kinase-3, an established substrate of PKB. However, the insulin-induced activation of PFK-2 was prevented only by KD PDK-1, but not by KD PKB. These results indicate that the insulin-induced activation of heart PFK-2 is mediated by a PDK-1-activated protein kinase other than PKB.