2-OMe-lysophosphatidylcholine analogues are GPR119 ligands and activate insulin secretion from βTC-3 pancreatic cells: Evaluation of structure-dependent biological activity

GPR119 receptor has been proposed as a metabolic regulator playing a pivotal role in the modulation of glucose homeostasis in type 2 diabetes. GPR119 was identified on pancreatic β cells and its ligands have the ability to enhance glucose-stimulated insulin secretion (GSIS). Lysophosphatidylcholine (LPC) was shown to potentiate GSIS and our present studies indicate that 2-methoxy-lysophosphatidylcholine (2-OMe-LPC) analogues, unable to undergo 1 → 2 acyl migration, stimulate GSIS from murine βTC-3 pancreatic cells even more efficiently. Moreover, biological assays in engineered Tango? GPR119-bla U2OS cells were carried out to ascertain the agonist activity of 2-OMe-LPC at GPR119. 2-OMe-LPC possessing in sn-1 position the residues of myristic, palmitic, stearic and oleic acid were also evaluated as factors regulating [Ca^2 +]_i mobilization and cAMP levels. Extension of these studies to R- and S-enantiomers of 14:0 2-OMe-LPC revealed that the overall impact on GSIS does not depend on chirality, however, the intracellular calcium mobilization data show that the R enantiomer is significantly more active than S one. Taking into account differences in chemical structure between various native LPCs and their 2-methoxy counterparts the possible binding mode of 2-OMe-LPC to the GPR119 receptor was determined using molecular modeling approach.     

β Subunit M2-M3 loop conformational changes are uncoupled from α1 β glycine receptor channel gating: implications for human hereditary hyperekplexia

Hereditary hyperekplexia, or startle disease, is a neuromotor disorder caused mainly by mutations that either prevent the surface expression of, or modify the function of, the human heteromeric α1 β glycine receptor (GlyR) chloride channel. There is as yet no explanation as to why hyperekplexia mutations that modify channel function are almost exclusively located in the α1 to the exclusion of β subunit. The majority of these mutations are identified in the M2-M3 loop of the α1 subunit. Here we demonstrate that α1 β GlyR channel function is less sensitive to hyperekplexia-mimicking mutations introduced into the M2-M3 loop of the β than into the α1 subunit. This suggests that the M2-M3 loop of the α subunit dominates the β subunit in gating the α1 β GlyR channel. A further attempt to determine the possible mechanism underlying this phenomenon by using the voltage-clamp fluorometry technique revealed that agonist-induced conformational changes in the β subunit M2-M3 loop were uncoupled from α1 β GlyR channel gating. This is in contrast to the α subunit, where the M2-M3 loop conformational changes were shown to be directly coupled to α1 β GlyR channel gating. Finally, based on analysis of α1 β chimeric receptors, we demonstrate that the structural components responsible for this are distributed throughout the β subunit, implying that the β subunit has evolved without the functional constraint of a normal gating pathway within it. Our study provides a possible explanation of why hereditary hyperekplexia-causing mutations that modify α1 β GlyR channel function are almost exclusively located in the α1 to the exclusion of the β subunit.     

Erratum to: Ozpolat B,Akar U,Mehta K,Lopez-Berenstein G. PKCδ and tissue transglutaminase are novel inhibitors of autophagy in pancreatic cancer cells. Autophagy 2007; 3:480-3

Ozpolat B, Akar U, Mehta K, Lopez-Berenstein G. PKCδ and tissue transglutaminase are novel inhibitors of autophagy in pancreatic cancer cells. Autophagy 2007; 3:480-3. This addendum included figures from a previously published paper but omitted the proper attribution to Akar U, Ozpolat B, Mehta K, Fok J, Kondo Y, Lopez-Berestein G. Tissue transglutaminase inhibits autophagy in pancreatic cancer cells. Mol Cancer Res 2007; 5:241-9. Fig. 1A and B were modified from Fig. 1A and B, Fig. 1C was taken from Fig. 4D, and Fig. 1D was from Fig. 3D. Fig. 2A and B were from Fig. 4A and Fig. 6, respectively. Finally, part of Fig. 3A was from Fig. 7A.     

O2 and H2O are each the source of one O in NO−2 produced from NH3 by Nitrosomonas: 15N-NMR evidence

The exchange of ¹⁸O between H₂¹⁸O and exogeneously added ¹⁵N¹⁶O^?₂ which occurs during oxidation of ammonia by Nitrosomonas is shown to occur one oxygen at a time. Conditions in which the exchange is diminished (notably the presence of ¹⁴NO^–₂ and CCCP) allowed demonstration that water and dioxygen are each the source of one oxygen in nitrite produced from ¹⁵NH₃. The nitrate produced in the presence of ¹⁸O₂ consisted of 67 and 0% ¹⁵N¹⁸O¹⁶O^? and ¹⁵N¹⁸O¹⁸O^?, respectively. Analysis was made using the ¹⁸O-isotope shift in ¹⁵N-NMR.