Comparative study of flux redistribution of metabolic pathway in glutamate production by two coryneform bacteria

In amino acid production by coryneform bacteria, study on relationship between change in enzyme activities and production of a target amino acid is important. In glutamate production, Kawahara et al. discovered that the effect of decrease in 2-oxoglutamate dehydrogenase complex (ODHC) on glutamate production is essential (Kawahara et al., Biosci. Biotechnol. Biochem. 61(7) (1997) 1109). Significant reduction of the ODHC activity was observed in the cells under the several glutamate-productive conditions in Corynebacterium glutamicum. Recent progress in metabolic engineering enables us to quantitatively compare the flux redistribution of the different strains after change in enzyme activity precisely. In this paper, relationship between flux redistribution and change in enzyme activities after biotin deletion and addition of detergent (Tween 40) was studied in two coryneform bacteria, C. glutamicum and a newly isolated strain, Corynebacterium efficiens (Fudou et al., Int. J. Syst. Evol. Microbiol. 52(Part 4) 1127), based on metabolic flux analysis (MFA). It was observed that in both species the specific activities of isocitrate dehydrogenase (ICDH) and glutamate dehydrogenase (GDH) did not significantly change throughout the fermentation, while that of the ODHC significantly decreased after biotin depletion and Tween 40 addition. Flux redistribution clearly occurred after the decrease in ODHC specific activity. The difference in glutamate production between C. glutamicum and C. efficiens was caused by the difference in the degree of decrease in ODHC specific activity. The difference in Michaelis-Menten constants or K(m) value between ICDH, GDH, and ODHC explained the mechanism of flux redistribution at the branch point of 2-oxoglutarate. It was found that the K(m) values of ICDH and ODHC were much lower than that of GDH for both strains. It was quantitatively proved that the ODHC plays the most important role in controlling flux distribution at the key branch point of 2-oxoglutarate in both coryneform bacteria. Flux redistribution mechanism was well simulated by a Michaelis-Menten-based model with kinetic parameters. The knowledge of the mechanism of flux redistribution will contribute to improvement of glutamate production in coryneform bacteria.     

A giant subcutaneous leiomyosarcoma arising in the inguinal region

BACKGROUND: Subcutaneous leiomyosarcoma is a rare condition that accounts for 1% to 2% of all superficial soft tissue malignancies. Approximately 10% of cases arise in the trunk, although the extremities are the most commonly affected. CASE PRESENTATION: We report herein the case of a 31-year-old man with a subcutaneous leiomyosarcoma, measuring 124 x 105 mm, arising in the left inguinal region. A wide local excision (with a resection margin >/= 20 mm) was performed. Histological examination of the resected specimen revealed a leiomyosarcoma with high cellularity and two mitoses per 10 high-power fields. The patient remains well with no evidence of disease 5 years and 8 months after the operation. CONCLUSION: This is the first reported case of subcutaneous leiomyosarcoma arising in the inguinal region and also one of the largest tumors reported. The experience of this case and a review of the English-language literature (PubMed, National Library of Medicine, Bethesda, MD, USA) suggest that a resection margin of >/= 10 mm is recommended when excising this rare tumor.     

Isoform-specific phosphorylation of metabotropic glutamate receptor 5 by protein kinase C (PKC) blocks Ca2+ oscillation and oscillatory translocation of Ca2+-dependent PKC

Prolonged activation of metabotropic glutamate receptor 5a (mGluR5a) causes synchronized oscillations in intracellular calcium, inositol 1,4,5-trisphosphate production, and protein kinase C (PKC) activation. Additionally, mGluR5 stimulation elicited cyclical translocations of myristoylated alanine-rich protein kinase C substrate, which were opposite to that of gammaPKC (i.e. from plasma membrane to cytosol) and dependent on PKC activity, indicating that myristoylated alanine-rich protein kinase C substrate is repetitively phosphorylated by oscillating gammaPKC on the plasma membrane. Mutation of mGluR5 Thr(840) to aspartate abolished the oscillation of gammaPKC, but the mutation to alanine (T840A) did not. Cotransfection of gammaPKC with betaIIPKC, another Ca2+-dependent PKC, resulted in synchronous oscillatory translocation of both classical PKCs. In contrast, cotransfection of deltaPKC, a Ca2+-independent PKC, abolished the oscillations of both gammaPKC and inositol 1,4,5-trisphosphate. Regulation of the oscillations was dependent on deltaPKC kinase activity but not on gammaPKC. Furthermore, the T840A-mGluR5-mediated oscillations were not blocked by the deltaPKC overexpression. These results revealed that activation of mGluR5 causes translocation of both gammaPKC and deltaPKC to the plasma membrane. deltaPKC, but not gammaPKC, phosphorylates mGluR5 Thr(840), leading to the blockade of both Ca2+ oscillations and gammaPKC cycling. This subtype-specific targeting proposes the molecular basis of the multiple functions of PKC.     

Activation and translocation of PKCdelta is necessary for VEGF-induced ERK activation through KDR in HEK293T cells

VEGF-KDR/Flk-1 signal utilizes the phospholipase C-gamma-protein kinase C (PKC)-Raf-MEK-ERK pathway as the major signaling pathway to induce gene expression and cPLA2 phosphorylation. However, the spatio-temporal activation of a specific PKC isoform induced by VEGF-KDR signal has not been clarified. We used HEK293T (human embryonic kidney) cells expressing transiently KDR to examine the activation mechanism of PKC. PKC specific inhibitors and human PKCdelta knock-down using siRNA method showed that PKCdelta played an important role in VEGF-KDR-induced ERK activation. Myristoylated alanine-rich C-kinase substrate (MARCKS) translocates from the plasma membrane to the cytoplasm depending upon phosphorylation by PKC. Translocation of MARCKS-GFP induced by VEGF-KDR stimulus was blocked by rottlerin, a PKCdelta specific inhibitor, or human PKCdelta siRNA. VEGF-KDR stimulation did not induce ERK phosphorylation in human PKCdelta-knockdown HEK293T cells, but co-expression of rat PKCdelta-GFP recovered the ERK phosphorylation. Y311/332F mutant of rat PKCdelta-GFP which cannot be activated by tyrosine-phosphorylation but activated by DAG recovered the ERK phosphorylation, while C1B-deletion mutant of rat PKCdelta-GFP, which can be activated by tyrosine-phosphorylation but not by DAG, failed to recover the ERK phosphorylation in human PKCdelta-knockdown HEK293T cell. These results indicate that PKCdelta is involved in VEGF-KDR-induced ERK activation via C1B domain.     

Superoxide production at phagosomal cup/phagosome through beta I protein kinase C during Fc gamma R-mediated phagocytosis in microglia

Protein kinase C (PKC) plays a prominent role in immune signaling. To elucidate the signal transduction in a respiratory burst and isoform-specific function of PKC during FcgammaR-mediated phagocytosis, we used live, digital fluorescence imaging of mouse microglial cells expressing GFP-tagged molecules. betaI PKC, epsilonPKC, and diacylglycerol kinase (DGK) beta dynamically and transiently accumulated around IgG-opsonized beads (BIgG). Moreover, the accumulation of p47(phox), an essential cytosolic component of NADPH oxidase and a substrate for betaI PKC, at the phagosomal cup/phagosome was apparent during BIgG ingestion. Superoxide (O(2)(-)) production was profoundly inhibited by G?6976, a cPKC inhibitor, and dramatically increased by the DGK inhibitor, R59949. Ultrastructural analysis revealed that BIgG induced O(2)(-) production at the phagosome but not at the intracellular granules. We conclude that activation/accumulation of betaI PKC is involved in O(2)(-) production, and that O(2)(-) production is primarily initiated at the phagosomal cup/phagosome. This study also suggests that DGKbeta plays a prominent role in regulation of O(2)(-) production during FcgammaR-mediated phagocytosis.     

Differential properties between TRK-820 and U-50,488H on the discriminative stimulus effects in rats

It has been demonstrated that the newly synthesized kappa-opioid receptor agonist TRK-820, which has a unique structure that is different from those of other prototypical kappa-opioid receptor agonists such as U-50,488H, exert some behavioral effects that differ from those induced by U-50,488H. Therefore, the present study was designed to examine the possible difference between the discriminative stimulus effects of TRK-820 and U-50,488H in rats. Substitution tests with several kappa-opioid receptor agonists were initiated in rats trained to discriminate between TRK-820 (40 microg/kg) or U-50,488H (3.0 mg/kg) and saline. In the cross-substitution tests, U-50,488H substituted for the discriminative stimulus effects of TRK-820, whereas TRK-820 did not substitute completely for those of U-50,488H, indicating that the discriminative stimulus effects of TRK-820 and U-50,488H were somewhat different. In the substitution tests, E-2078, but not R-84760, substituted for the discriminative stimulus effects of both TRK-820 and U-50,488H. KT-90, CI-977 and ICI-199441 each substituted for the discriminative stimulus effects of U-50,488H, but not to those of TRK-820. These results imply that these kappa-opioid receptor agonists possess U-50,488H-like discriminative stimulus effects. Furthermore, that U-50,488H and the other kappa-opioid receptor agonists substituted for the discriminative stimulus effects of U-50,488H, produced aversive effects in rats. These findings suggest the possibility that unlike those of TRK-820, the cue of the discriminative stimulus effects of U-50,488H may be, at least in part, associated with its aversive effects.     

Cell elongation and cell death of helicobacter pylori is modulated by the disruption of cdrA (cell division-related gene A)

The cell division-related gene A (cdrA) of Helicobacter pylori is dispensable in vivo and unique in having a repressive role on cell division and long-term survival. To clarify its role, comparisons of the wildtype HPK5 and isogenic cdrA-disrupted mutant HPKT510 were examined by ultrastructural morphology, PBP profiles, and susceptibility to beta-lactam antibiotics during long-term cultivation. Ultrastructural analyses revealed that the shorter rods of HPKT510 had a slightly wider periplasmic space between the inner and the outer membrane than those of HPK5. Cell division of HPKT510 cells was complete even under high-salt conditions in which HPK5 cells became filamentous due to inhibition of division. The filamentous HPK5 cells constructed an inner membrane without a cell wall at the presumed division site. After 4 days of cultivation (the late stationary phase), most of the HPK5 cells turned into ghosts and aggregates, while some of the HPKT510 cells remained as curved rods, which coincided with the results of cell viability. HPKT510 cells became resistant to ampicillin killing compared to HPK5 cells, although their minimum inhibitory concentrations (MICs) and PBP profiles were not significantly different. These results suggest that the cdrA product represses cell division via inhibiting cell wall synthesis at division site. During infection in both mice and humans, inactivation of cdrA eventually gains biological aspects such as increased viability, long-term survival and tolerance to antibiotics and high-salt condition, which might enhance a persistent infection.