Kegg Pathway: Inositol phosphate metabolism

Endocrinology. 2009 Oct 30;
Rafacho A, Marroquí L, Taboga SR, Abrantes JL, Silveira LR, Boschero AC, Carneiro EM, Bosqueiro JR, Nadal A, Quesada I

Although glucocorticoids are widely used as antiinflammatory agents in clinical therapies, they may cause serious side effects that include insulin resistance and hyperinsulinemia. To study the potential functional adaptations of the islet of Langerhans to in vivo glucocorticoid treatment, adult Wistar rats received dexamethasone (DEX) for 5 consecutive days, whereas controls (CTL) received only saline. The analysis of insulin release in freshly isolated islets showed an enhanced secretion in response to glucose in DEX-treated rats. The study of Ca(2+) signals by fluorescence microscopy also demonstrated a higher response to glucose in islets from DEX-treated animals. However, no differences in Ca(2+) signals were found between both groups with tolbutamide or KCl, indicating that the alterations were probably related to metabolism. Thus, mitochondrial function was explored by monitoring oxidation of nicotinamide dinucleotide phosphate autofluorescence and mitochondrial membrane potential. Both parameters revealed a higher response to glucose in islets from DEX-treated rats. The mRNA and protein content of glucose transporter-2, glucokinase, and pyruvate kinase was similar in both groups, indicating that changes in these proteins were probably not involved in the increased mitochondrial function. Additionally, we explored the status of Ca(2+)-dependent signaling kinases. Unlike calmodulin kinase II, we found an augmented phosphorylation level of protein kinase Calpha as well as an increased response of the phospholipase C/Inositol 1,4,5-triphosphate pathway in DEX-treated rats. Finally, an increased number of docked secretory granules were observed in the beta-cells of DEX animals using transmission electron microscopy. Thus, these results demonstrate that islets from glucocorticoid-treated rats develop several adaptations that lead to an enhanced stimulus-secretion coupling and secretory capacity.

J Cell Mol Med. 2009 Oct 20;
Catchpole G, Platzer A, Weikert C, Kempkensteffen C, Johannsen M, Krause H, Jung K, Miller K, Willmitzer L, Selbig J, Weikert S

Abstract Recent evidence suggests that metabolic changes play a pivotal role in the biology of cancer and in particular renal cell carcinoma (RCC). Here, a global metabolite profiling approach was applied to characterize the metabolite pool of RCC and normal renal tissue. Advanced decision tree models were applied to characterize the metabolic signature of RCC and to explore features of metastasized tumors. The findings were validated in a second independent dataset. Vitamin E derivates and metabolites of glucose, fatty acid, and Inositol phosphate metabolism determined the metabolic profile of RCC. Alpha-tocopherol, hippuric acid, myoInositol, fructose-1-phosphate, and glucose-1-phosphate contributed most to the tumor/normal discrimination and all showed pronounced concentration changes in RCC. The identified metabolic profile was characterized by a low recognition error of only 5% for tumor versus normal samples. Data on metastasized tumors suggested a key role for metabolic pathways involving arachidonic acid, free fatty acids, proline, uracil, and the tricarboxylic acid cycle. These results illustrate the potential of mass spectroscopy based metabolomics in conjunction with sophisticated data analysis methods to uncover the metabolic phenotype of cancer. Differentially regulated metabolites, such as vitamin E compounds, hippuric acid, and myoInositol, provide leads for the characterization of novel pathways in RCC.

J Clin Endocrinol Metab. 2009 Oct 16;
Kemp EH, Gavalas NG, Krohn KJ, Brown EM, Watson PF, Weetman AP

Context: Autoimmune polyendocrine syndrome type 1 (APS1) is an autosomal recessive disorder caused by mutations in the autoimmune regulator (AIRE) gene. Hypoparathyroidism occurs in 80% of patients with APS1 and has been suggested to result from an autoimmune reaction against the calcium-sensing receptor (CaSR) in parathyroid cells. Anti-CaSR binding antibodies have previously been detected in patients with APS1. Objective: The aim of this study was to determine whether anti-CaSR antibodies present in APS1 patients could modulate the response of the CaSR to stimulation by Ca(2+). Results: The results indicated that two of the 14 APS1 patients included in the study had anti-CaSR antibodies that stimulated the receptor. These antibodies were detected by their ability to increase both Ca(2+)-dependent extracellular signal-regulated kinase phosphorylation and Inositol phosphate accumulation in human embryonic kidney 293 cells expressing the CaSR. Conclusion: An important implication of the present results is that although the majority of APS1 patients do not have CaSR-stimulating antibodies, there may be a small but substantial minority of patients in whom the hypoparathyroid state is the result of functional suppression of the parathyroid glands rather than their irreversible destruction.

Vet Parasitol. 2009 Sep 19;
Rodríguez AE, Couto A, Echaide I, Schnittger L, Florin-Christensen M

Autonomous glycosylphosphatidylInositol (GPI) molecules (also protein-free GPIs or free GPIs) have been reported to be particularly abundant in some parasitic protozoa and mediate strong immunomodulatory effects on the host immune system. In the work at hand we have investigated the existence of free GPIs in Babesia bovis. Comparative thin layer chromatographic analysis of the protein-free glycolipid fraction of in vitro cultured B. bovis merozoites and erythrocyte membranes demonstrated the presence of an abundant parasite-specific band. Its chemical analysis revealed a GPI species containing a chain of two mannose residues, N-glucosamine and non-acylated Inositol. The lipid moiety linked to Inositol was diacylglycerol. The total fatty acid composition showed predominantly long-carbon chain molecules (12% of C(22:0) and 45% of C(24:0)). The potential of B. bovis to assemble the presented free GPI species was verified by the existence of seven genes in its genome that putatively encode the following GPI biosynthetic enzymes: PI N-acetyl-GlcN-transferase (PIG-A and GPI-1), N-acetyl-GlcN-PI-de-N-acetylase (PIG-L), acyltransferase (PIG-W), dolichyl-phosphate mannosyl transferase (DPM-1), GPI mannosyltransferase I (PIG-M), and GPI mannosyltransferase II (PIG-V). GPI biosynthesis is vital for the intraerythrocytic parasite stage as mannosamine, an inhibitor of GPI biosynthesis, impaired in vitro growth of B. bovis merozoites. Absence of the vast majority of N-glycan metabolism encoding genes in the B. bovis genome underscores that the growth inhibitory effect of mannosamine is attributable to its interference with GPI biosynthesis and not with assembly of N-linked oligosaccharides, as has been described for higher eukaryotes. Elucidation of the structure and biosynthesis of GPI may allow to facilitate the development of future immune interventions against bovine babesiosis.

Immunol Rev. 2009 Sep; 231(1): 45-58
Di Capite J, Parekh AB

Mast cells are integral members of the immune system. Upon activation by a rise in cytoplasmic Ca2+, they release a battery of paracrine signals, chemokines, and cytokines, which help sculpt the subsequent immune response. Ca2+ entry through store-operated Ca2+ release-activated Ca2+ (CRAC) channels in the plasma membrane is central for driving most of these responses. The molecular basis of the CRAC channel has been identified, with Orai1 forming the channel pore. Recent work has revealed that a range of mast cell responses are activated by spatially restricted Ca2+ signals just below the plasma membrane. These Ca2+ microdomains can activate cytosolic enzymes, leading to the generation of intracellular messengers as well as proinflammatory molecules like LTC4. In this review, we describe key features of CRAC channels in mast cells, how they generate local Ca2+ signals, and how the cell can decode these restricted signals to generate a raft of responses.

Biochem Soc Trans. 2009 Oct; 37(Pt 5): 1115-20
Kleineidam A, Vavassori S, Wang K, Schweizer LM, Griac P, Schweizer M

Prs [PRPP (phosphoribosyl pyrophosphate) synthetase] catalyses the transfer of pyrophosphate from ATP to ribose 5-phosphate, thereby activating the pentose sugar for incorporation into purine and pyrimidine nucleotides. The Saccharomyces cerevisiae genome contains five genes, PRS1-PRS5, whose products display characteristic PRPP and bivalent-cation-binding sites of Prs polypeptides. Deletion of one or more of the five PRS genes has far-reaching and unexpected consequences, e.g. impaired cell integrity, temperature-sensitivity and sensitivity to VPA (valproic acid) and LiCl. CTP pools in prs1Delta and prs3Delta are reduced to 12 and 31% of the wild-type respectively, resulting in an imbalance in phospholipid metabolism which may have an impact on the intracellular Inositol pool which is affected by the administration of either VPA or LiCl. Overexpression of CTP synthetase in prs1Delta prs3Delta strains partially reverses the VPA-sensitive phenotype. Yeast two-hybrid screening revealed that Prs3 and the yeast orthologue of GSK3 (glycogen synthase kinase 3), Rim11, a serine/threonine kinase involved in several signalling pathways, interact with each other. Furthermore, Prs5, an essential partner of Prs3, which also interacts with GSK3 contains three neighbouring phosphorylation sites, typical of GSK3 activation. These studies on yeast PRPP synthetases bring together and expand the current theories for the mood-stabilizing effects of VPA and LiCl in bipolar disorder.

J Inorg Biochem. 2009 Nov; 103(11): 1497-503
Chee-González L, Muñoz-Sánchez JA, Racagni-Di Palma G, Hernández-Sotomayor SM

In acid soils, aluminium (Al) toxicity and phosphate (Pi) deficiency are the most significant constraints on plant growth. Al inhibits cell growth and disrupts signal transduction processes, thus interfering with metabolism of phospholipase C (PLC), an enzyme involved in second messenger production in the cell. Using a Coffea arabica suspension cell model, we demonstrate that cell growth inhibition by Al toxicity is mitigated at a high Pi concentration. Aluminium-induced cell growth inhibition may be due to culture medium Pi deficiency, since Pi forms complexes with Al, reducing Pi availability to cells. phosphate does not mitigate inhibition of PLC activity by Al toxicity. Other enzymes of the phosphoinositide signal transduction pathway were also evaluated. Aluminium disrupts production of second messengers such as Inositol 1,4,5-trisphosphate (IP(3)) and phosphatidic acid (PA) by blocking PLC activity; however, phospholipase D (PLD) and diacylglycerol kinase (DGK) activities are stimulated by Al, a response probably aimed at counteracting Al effects on PA formation. phosphate deprivation also induces PLC and DGK activity. These results suggest that Al-induced cell growth inhibition is not linked to PLC activity inhibition.

J Microbiol Methods. 2009 Oct; 79(1): 106-10
Cao SS, Hu ZQ

An optimized Citrobacter braakii phytase gene, appA-c, was chemically synthesized by oligonucleotides synthesis and over-lap PCR method. The appA-c gene encoding 423 amino acids was cloned into expression vector pPIC9 and transformed into methylotropic yeast Pichia pastoris. From about 2000 transformants, 400 transformants exhibiting phytase activity were obtained. One transformant showing the strongest phytase activity was selected for detailed analyses in 5 L bioreactor. Under control of the highly-inducible alcohol oxidase gene (AOX1) promoter, the transformant was able to secrete 3.85 mg/ml protein to the culture supernatant in about 110 h methanol induction, which comprises of 12,116 U ml(-1) phytase activity. Further characterization of the recombinant phytase was conducted. The optimal pH and temperature for this recombinant phytase was about 4.0 and 50 degrees C, respectively. Fe3+, Zn2+ and Cu2+ could significantly inhibit the recombinant phytase enzyme activity. The specific activity of this recombinant enzyme was 3147 U mg(-1). The K(m) and V(max) values for sodium phytate were determined to be 0.5 mM and 3085 U/mg, respectively. To our knowledge, this is the first report of a chemically synthesized C. braakii appA gene heterologous expression with the highest expression level and highest phytase activity achieved. The novel gene optimization and synthesis method can be applied to other related researches.

PLoS Genet. 2009 Sep; 5(9): e1000636
Walker DS, Vázquez-Manrique RP, Gower NJ, Gregory E, Schafer WR, Baylis HA

When Caenorhabditis elegans encounters an unfavourable stimulus at its anterior, it responds by initiating an avoidance response, namely reversal of locomotion. The amphid neurons, ASHL and ASHR, are polymodal in function, with roles in the avoidance responses to high osmolarity, nose touch, and both volatile and non-volatile repellents. The mechanisms that underlie the ability of the ASH neurons to respond to such a wide range of stimuli are still unclear. We demonstrate that the Inositol 1,4,5-trisphosphate receptor (IP(3)R), encoded by itr-1, functions in the reversal responses to nose touch and benzaldehyde, but not in other known ASH-mediated responses. We show that phospholipase Cbeta (EGL-8) and phospholipase Cgamma (PLC-3), which catalyse the production of IP(3), both function upstream of ITR-1 in the response to nose touch. We use neuron-specific gene rescue and neuron-specific disruption of protein function to show that the site of ITR-1 function is the ASH neurons. By rescuing plc-3 and egl-8 in a neuron-specific manner, we show that both are acting in ASH. Imaging of nose touch-induced Ca(2+) transients in ASH confirms these conclusions. In contrast, the response to benzaldehyde is independent of PLC function. Thus, we have identified distinct roles for the IP(3)R in two specific responses mediated by ASH.

Diabetes. 2009 Nov; 58(11): 2607-15
Alquier T, Peyot ML, Latour MG, Kebede M, Sorensen CM, Gesta S, Ronald Kahn C, Smith RD, Jetton TL, Metz TO, Prentki M, Poitout V

OBJECTIVE: The G-protein-coupled receptor GPR40 mediates fatty acid potentiation of glucose-stimulated insulin secretion, but its contribution to insulin secretion in vivo and mechanisms of action remain uncertain. This study was aimed to ascertain whether GPR40 controls insulin secretion in vivo and modulates intracellular fuel metabolism in islets. RESEARCH DESIGN AND METHODS: Insulin secretion and sensitivity were assessed in GPR40 knockout mice and their wild-type littermates by hyperglycemic clamps and hyperinsulinemic euglycemic clamps, respectively. Transcriptomic analysis, metabolic studies, and lipid profiling were used to ascertain whether GPR40 modulates intracellular fuel metabolism in islets. RESULTS: Both glucose- and arginine-stimulated insulin secretion in vivo were decreased by approximately 60% in GPR40 knockout fasted and fed mice, without changes in insulin sensitivity. Neither gene expression profiles nor intracellular metabolism of glucose and palmitate in isolated islets were affected by GPR40 deletion. Lipid profiling of isolated islets revealed that the increase in triglyceride and decrease in lyso-phosphatidylethanolamine species in response to palmitate in vitro was similar in wild-type and knockout islets. In contrast, the increase in intracellular Inositol phosphate levels observed in wild-type islets in response to fatty acids in vitro was absent in knockout islets. CONCLUSIONS: These results indicate that deletion of GPR40 impairs insulin secretion in vivo not only in response to fatty acids but also to glucose and arginine, without altering intracellular fuel metabolism in islets, via a mechanism that may involve the generation of Inositol phosphates downstream of GPR40 activation.

Proc Natl Acad Sci U S A. 2009 Sep 15; 106(37): 15950-5
Ma L, Seager MA, Wittmann M, Jacobson M, Bickel D, Burno M, Jones K, Graufelds VK, Xu G, Pearson M, McCampbell A, Gaspar R, Shughrue P, Danziger A, Regan C, Flick R, Pascarella D, Garson S, Doran S, Kreatsoulas C, Veng L, Lindsley CW, Shipe W, Kuduk S, Sur C, Kinney G, Seabrook GR, Ray WJ

The forebrain cholinergic system promotes higher brain function in part by signaling through the M(1) muscarinic acetylcholine receptor (mAChR). During Alzheimer's disease (AD), these cholinergic neurons degenerate, therefore selectively activating M(1) receptors could improve cognitive function in these patients while avoiding unwanted peripheral responses associated with non-selective muscarinic agonists. We describe here benzyl quinolone carboxylic acid (BQCA), a highly selective allosteric potentiator of the M(1) mAChR. BQCA reduces the concentration of ACh required to activate M(1) up to 129-fold with an inflection point value of 845 nM. No potentiation, agonism, or antagonism activity on other mAChRs is observed up to 100 microM. Furthermore studies in M(1)(-/-) mice demonstrates that BQCA requires M(1) to promote Inositol phosphate turnover in primary neurons and to increase c-fos and arc RNA expression and ERK phosphorylation in the brain. Radioligand-binding assays, molecular modeling, and site-directed mutagenesis experiments indicate that BQCA acts at an allosteric site involving residues Y179 and W400. BQCA reverses scopolamine-induced memory deficits in contextual fear conditioning, increases blood flow to the cerebral cortex, and increases wakefulness while reducing delta sleep. In contrast to M(1) allosteric agonists, which do not improve memory in scopolamine-challenged mice in contextual fear conditioning, BQCA induces beta-arrestin recruitment to M(1), suggesting a role for this signal transduction mechanism in the cholinergic modulation of memory. In summary, BQCA exploits an allosteric potentiation mechanism to provide selectivity for the M(1) receptor and represents a promising therapeutic strategy for cognitive disorders.

Proteomics. 2009 Aug; 9(16): 4000-16
Hakimov HA, Walters S, Wright TC, Meidinger RG, Verschoor CP, Gadish M, Chiu DK, Strömvik MV, Forsberg CW, Golovan SP

In this study iTRAQ was used to produce a highly confident catalogue of 542 proteins identified in porcine muscle (false positive<5%). To our knowledge this is the largest reported set of skeletal muscle proteins in livestock. Comparison with human muscle proteome demonstrated a low level of false positives with 83% of the proteins common to both proteomes. In addition, for the first time we assess variations in the muscle proteome caused by sexually dimorphic gene expression and diet dephytinization. Preliminary analysis identified 19 skeletal muscle proteins differentially expressed between male and female pigs (> or = 1.2-fold, p<0.05), but only one of them, GDP-dissociation inhibitor 1, was significant (p<0.05) after false discovery rate correction. Diet dephytinization affected expression of 20 proteins (p<0.05). This study would contribute to an evaluation of the suitability of the pig as a model to study human gender-related differences in gene expression. Transgenic pigs used in this study might also serve as a useful model to understand changes in human physiology resulting from diet dephytinization.

J Neurochem. 2009 Oct; 111(2): 555-67
Canela L, Fernández-Dueñas V, Albergaria C, Watanabe M, Lluís C, Mallol J, Canela EI, Franco R, Luján R, Ciruela F

Metabotropic glutamate (mGlu) receptors mediate in part the CNS effects of glutamate. These receptors interact with a large array of intracellular proteins in which the final role is to regulate receptor function. Here, using co-immunoprecipitation and pull-down experiments we showed a close and specific interaction between mGlu(5) receptor and NECAB2 in both transfected human embryonic kidney cells and rat hippocampus. Interestingly, in pull-down experiments increasing concentrations of calcium drastically reduced the ability of these two proteins to interact, suggesting that NECAB2 binds to mGlu(5) receptor in a calcium-regulated manner. Immunoelectron microscopy detection of NECAB2 and mGlu(5) receptor in the rat hippocampal formation indicated that both proteins are codistributed in the same subcellular compartment of pyramidal cells. In addition, the NECAB2/mGlu(5) receptor interaction regulated mGlu(5b)-mediated activation of both Inositol phosphate accumulation and the extracellular signal-regulated kinase/mitogen-activated protein kinase pathway. Overall, these findings indicate that NECAB2 by its physical interaction with mGlu(5b) receptor modulates receptor function.

Food Nutr Bull. 2009 Jun; 30(2): 145-52
Lung'aho MG, Glahn RP

BACKGROUND: Iron-deficiency anemia is by far the most widespread micronutrient deficiency disease in the world, affecting more than 2 billion people. Although there are multiple causes of anemia, its high prevalence among children-especially in developing countries such as Kenya-is attributed to an inadequate intake of dietary iron. OBJECTIVE: The main objective of this study was to assess the amount of bioavailable iron in Kenyan complementary foods and to determine whether strategies such as food diversification using locally available foods would improve the bioavailability of iron from these foods. METHODS: The in vitro iron bioavailability system/ Caco-2 cell model that mirrors the gastric and intestinal digestion of humans was used in this study to estimate the amount of bioavailable iron in the porridges. RESULTS: The addition of cassava significantly increased the amount of ferritin formation in a cereal-based home recipe from 36.74 to 67.58 ng/mg. The in vitro data suggests that home recipes can provide an equal or greater amount of bioavailable iron as the commercially available nonfortified porridge products. However, in vitro assessment showed that the nonfortified recipes had less bioavailable iron than Cerelac, a commercially available fortified complementary food that provides about 26% of the RDA of iron for infants 6 and 7 months of age per serving (p < .0001). CONCLUSIONS: In addition to diet diversity, more approaches to address iron inadequacy of complementary foods are required to improve the bioavailability of iron from the Kenyan complementary foods analyzed.

Int J Food Microbiol. 2009 Sep 30; 135(1): 7-14
Haros M, Carlsson NG, Almgren A, Larsson-Alminger M, Sandberg AS, Andlid T

The growing awareness of the relationship between diet and health has led to an increasing demand for food products that support health above and beyond providing basic nutrition. Probiotics are live organisms present in foods, which yield health benefits related to their interactions with the gastrointestinal tract. Phytases are a subgroup of phosphatases that catalyse the desphosphorylation of phytate, which reduces its negative impact on mineral bioavailability, and generates lower Inositol phosphates. The aims of this investigation were to (i) study the ability of the probiotic candidate Bifidobacterium pseudocatenulatum to degrade phytate in synthetic medium, to (ii) identify the lower Inositol phosphates generated, to (iii) study its survival under conditions mimicking gastrointestinal passage and finally to (iv) assess adhesion of the bacteria to Caco-2 cells. The first steps of InsP(6) degradation by B. pseudocatenulatum phytate-degrading enzyme/s were preferentially initiated at the DL-6-position and 5-position of the myo-Inositol ring. It suggests that the main InsP(6) degradation pathway by B. pseudocatenulatum by sequential removal of phosphate groups was D/L-Ins(1,2,3,4,5)P(5) or D/L-Ins(1,2,3,4,6)P(5); D/L-Ins(1,2,3,4)P(4); to finally Ins(1,2,3)P(3) and D/L-Ins(1,2,4)P(3)/D/L-Ins(1,3,4)P(3). This human strain also showed a notable tolerance to bile as well as a selective adhesion capacity (adhesion to control surfaces was zero), to human intestinal Caco-2 cells comparable to the commercial probiotic B. lactis. The phytate-degrading activity constitutes a novel metabolic trait which could contribute to the improvement of mineral absorption in the intestine as a nutritional probiotic feature with potential trophic effect in human gut.

Nat Genet. 2009 Sep; 41(9): 1032-6
Bielas SL, Silhavy JL, Brancati F, Kisseleva MV, Al-Gazali L, Sztriha L, Bayoumi RA, Zaki MS, Abdel-Aleem A, Rosti RO, Kayserili H, Swistun D, Scott LC, Bertini E, Boltshauser E, Fazzi E, Travaglini L, Field SJ, Gayral S, Jacoby M, Schurmans S, Dallapiccola B, Majerus PW, Valente EM, Gleeson JG

PhosphotidylInositol (PtdIns) signaling is tightly regulated both spatially and temporally by subcellularly localized PtdIns kinases and phosphatases that dynamically alter downstream signaling events. Joubert syndrome is characterized by a specific midbrain-hindbrain malformation ('molar tooth sign'), variably associated retinal dystrophy, nephronophthisis, liver fibrosis and polydactyly and is included in the newly emerging group of 'ciliopathies'. In individuals with Joubert disease genetically linked to JBTS1, we identified mutations in the INPP5E gene, encoding Inositol polyphosphate-5-phosphatase E, which hydrolyzes the 5-phosphate of PtdIns(3,4,5)P3 and PtdIns(4,5)P2. Mutations clustered in the phosphatase domain and impaired 5-phosphatase activity, resulting in altered cellular PtdIns ratios. INPP5E localized to cilia in major organs affected by Joubert syndrome, and mutations promoted premature destabilization of cilia in response to stimulation. These data link PtdIns signaling to the primary cilium, a cellular structure that is becoming increasingly recognized for its role in mediating cell signals and neuronal function.

Development. 2009 Sep; 136(17): 3007-17
Mei W, Lee KW, Marlow FL, Miller AL, Mullins MC

Egg activation is an important cellular event required to prevent polyspermy and initiate development of the zygote. Egg activation in all animals examined is elicited by a rise in free Ca(2+) in the egg cytosol at fertilization. This Ca(2+) rise is crucial for all subsequent egg activation steps, such as cortical granule exocytosis, which modifies the vitelline membrane to prevent polyspermy. The cytosolic Ca(2+) rise is primarily initiated by Inositol 1,4,5-trisphosphate (IP(3))-mediated Ca(2+) release from the endoplasmic reticulum. The genes involved in regulating the IP(3)-mediated Ca(2+) release during egg activation remain largely unknown. Here we report on a zebrafish maternal-effect mutant, brom bones, which is defective in the cytosolic Ca(2+) rise and subsequent egg activation events, including cortical granule exocytosis and cytoplasmic segregation. We show that the egg activation defects in brom bones can be rescued by providing Ca(2+) or the Ca(2+)-release messenger IP(3), suggesting that brom bones is a regulator of IP(3)-mediated Ca(2+) release at fertilization. Interestingly, brom bones mutant embryos also display defects in dorsoventral axis formation accompanied by a disorganized cortical microtubule network, which is known to be crucial for dorsal axis formation. We provide evidence that the impaired microtubule organization is associated with non-exocytosed cortical granules from the earlier egg activation defect. Positional cloning of the brom bones gene reveals that a premature stop codon in the gene encoding hnRNP I (referred to here as hnrnp I) underlies the abnormalities. Our studies therefore reveal an important new role of hnrnp I in regulating the fundamental process of IP(3)-mediated Ca(2+) release at egg activation.

Int J Food Microbiol. 2009 Sep 30; 135(1): 28-33
Tamang JP, Tamang B, Schillinger U, Guigas C, Holzapfel WH

A total of 94 strains of Lactic acid bacteria (LAB), previously isolated from ethnic fermented vegetables and tender bamboo shoots of the Himalayas, were screened for functional properties such as acidification capacity, enzymatic activities, degradation of antinutritive factors and oligosaccharides, production of biogenic amines, hydrophobicity and adherence to mucus secreting HT29 MTX cells. Strong acidification and coagulation activities of LAB strains were recorded. Most of the LAB strains showed antimicrobial activities against the used indicator strains; however, only Lb. plantarum IB2 (BFE 948) isolated from inziangsang, a fermented leafy vegetable product, produced a bacteriocin against Staphylococcus aureus S1. LAB strains showed enzymatic activities and also degraded oligosaccharides. Almost all the strains of LAB were non-producers of biogenic amines except few strains. Some strains of Lb. plantarum showed more than 70% hydrophobicity. Adherence to the mucus secreting HT29 MTX cells was also shown by seven strains indicating their probiotic nature.

Biochemistry. 2009 Sep 8; 48(35): 8282-4
Pu M, Feng J, Redfield AG, Roberts MF

31P NMR relaxation studies from 0.005 to 11.7 T are used to monitor water-soluble Inositol 1,2-(cyclic) phosphate (cIP) binding to phosphatidylInositol-specific phospholipase C spin-labeled at H82C, a position near the active site of the enzyme, and to determine how activating phosphatidylcholine (PC) molecules affect this interaction. We show that, in the absence of an interface, cIP binding to the protein is not rate-limiting, and that lower activation by PC vesicles as opposed to micelles is likely due to hindered product release. The methodology is general and could be used for determining distances in other weakly binding small molecule ligand-protein interactions.

Biophys J. 2009 Aug 5; 97(3): 722-9
Fendler B, Zhang M, Satin L, Bertram R

Plasma insulin measurements from mice, rats, dogs, and humans indicate that insulin levels are oscillatory, reflecting pulsatile insulin secretion from individual islets. An unanswered question, however, is how the activity of a population of islets is coordinated to yield coherent oscillations in plasma insulin. Here, using mathematical modeling, we investigate the feasibility of a potential islet synchronization mechanism, cholinergic signaling. This hypothesis is based on well-established experimental evidence demonstrating intrapancreatic parasympathetic (cholinergic) ganglia and recent in vitro evidence that a brief application of a muscarinic agonist can transiently synchronize islets. We demonstrate using mathematical modeling that periodic pulses of acetylcholine released from cholinergic neurons is indeed able to coordinate the activity of a population of simulated islets, even if only a fraction of these are innervated. The role of islet-to-islet heterogeneity is also considered. The results suggest that the existence of cholinergic input to the pancreas may serve as a regulator of endogenous insulin pulsatility in vivo.