Protein-tyrosine phosphatase-1B (PTP1B) mediates the anti-migratory actions of Sprouty

Mammalian Sprouty proteins have been shown to inhibit the proliferation and migration of cells in response to growth factors and serum. In this communication, using HeLa cells, we have examined the possibility that human Sprouty 2 (hSPRY2) mediates its anti-migratory actions by modulating the activity or intracellular localization of protein-tyrosine phosphatases. In HeLa cells, overexpression of hSPRY2 resulted in an increase in protein-tyrosine phosphatase (PTP1B) amount and activity in the soluble (100,000 x g) fraction of cells without an increase in total amount of cellular PTP1B. This increase in the soluble form of PTP1B was accompanied by a decrease in the amount of the enzyme in the particulate fraction. The amounts of PTP-PEST or PTP1D in the soluble fractions were not altered. Consistent with an increase in soluble PTP1B amount and activity, the tyrosine phosphorylation of cellular proteins and p130(Cas) was decreased in hSPRY2-expressing cells. In control cells, overexpression of wild-type (WT) PTP1B, but not its C215S catalytically inactive mutant mimicked the actions of hSPRY2 on tyrosine phosphorylation of cellular proteins and migration. On the other hand, in hSPRY2-expressing cells, the C215S mutant, but not WT PTP1B, increased tyrosine phosphorylation of cellular proteins and attenuated the anti-migratory actions of hSPRY2. Interestingly, neither WT nor C215S mutant forms of PTP1B modulated the anti-mitogenic actions of hSPRY2. Therefore, we conclude that an increase in soluble PTP1B activity contributes to the anti-migratory, but not anti-mitogenic, actions of hSPRY2.     

Genetic diversity of the human serotonin receptor 1B (HTR1B) gene

We systematically and comprehensively investigated polymorphisms of the HTR1B gene as well as their linkage disequilibrium and ancestral relationships. We have detected the following polymorphisms in our sample via denaturing gradient gel electrophoresis, database comparisons, and/or previously published assays: G-511T, T-261G, -182INS/DEL-181, A-161T, C129T, T371G, T655C, C705T, G861C, A1099G, G1120A, and A1180G. The results of the intermarker analyses showed strong linkage disequilibrium between the C129T and the G861C polymorphisms and revealed four common haplotypes: ancestral (via chimpanzee comparisons), 129T/861C, -161T, and -182DEL-181. The results of association tests with schizophrenia were negative, although A-161T had a nominal P = 0.04 via ASPEX/sib_tdt. The expressed missense substitutions, Phe124Cys, Phe219Leu, Ile367Val, and Glu374Lys, could potentially affect ligand binding or interaction with G proteins and thus modify drug response in carriers of these variants. On average, the human cSNPs and differences among other primates clustered in the more thermodynamically unstable regions of the mRNA, which suggests that the evolutionary survival of nucleotide sequence variation may be influenced by the mRNA structure of this gene.     

Alternative pathways of glucose transport in Prevotella bryantii B(1)4(1)

Prevotella bryantii B(1)4 grew faster on glucose than mannose (0.70 versus 0.45 h(-1)), but these sugars were used simultaneously rather than diauxically. 2-deoxy-glucose (2DG) decreased the growth rate of cells that were provided with either glucose or mannose, but 2DG did not completely prevent growth. Cells grown on glucose or mannose transported both (14)C-glucose and (14)C-mannose, but cells grown on glucose had over three-fold higher rates of (14)C-glucose transport than cells grown on mannose. The (14)C-mannose transport rates of glucose- and mannose-grown cells were similar. Woolf-Augustinsson-Hofstee plots were not linear, and it appeared that the glucose/mannose/2DG carrier acted as a facilitated diffusion system at high substrate concentrations. When cultures were grown on nitrogen-deficient (excess sugar) medium, isolates had three-fold lower (14)C-glucose transport, but the (14)C-mannose transport did not change significantly. (14)C-glucose and (14)C-mannose transport rates could be inhibited by 2DG and either mannose or glucose, respectively. The (14)C-glucose transport of mannose-grown cells was inhibited more strongly by mannose and 2DG than those grown on glucose. Cells grown on glucose or mannose had similar ATP-dependent glucokinase activity, and 2DG was a competitive inhibitor (K(i)=0.75 mM). Thin layer chromatography indicated that cell extracts also had ATP-dependent mannose phosphorylation, but only a small amount of phosphorylated 2DG was detected. Glucose, mannose or 2DG were not phosphorylated in the presence of PEP. Based on these results, it appeared that P. bryantii B(1)4 had: (1) two mechanisms of glucose transport, a constitutive glucose/mannose/2DG carrier and an alternative glucose carrier that was regulated by glucose availability, (2) an ATP-dependent glucokinase that was competitively inhibited by 2DG but was unable to phosphorylate 2DG at a rapid rate, and (3) virtually no PEP-dependent glucose, mannose or 2DG phosphorylation activities.     

Das Aneurin (Vitamin B1)

Reviews of Physiology, Biochemistry and Pharmacology -