TIP47 is a key effector for Rab9 localization

The human genome encodes approximately 70 Rab GTPases that localize to the surfaces of distinct membrane compartments. To investigate the mechanism of Rab localization, chimeras containing heterologous Rab hypervariable domains were generated, and their ability to bind seven Rab effectors was quantified. Two chimeras could bind effectors for two distinctly localized Rabs; a Rab5/9 hybrid bound both Rab5 and Rab9 effectors, and a Rab1/9 hybrid bound to certain Rab1 and Rab9 effectors. These unusual chimeras permitted a test of the importance of effector binding for Rab localization. In both cases, changing the cellular concentration of a key Rab9 effector, which is called tail-interacting protein of 47 kD, moved a fraction of the proteins from their parental Rab localization to that of Rab9. Thus, relative concentrations of certain competing effectors could determine a chimera's localization. These data confirm the importance of effector interactions for Rab9 localization, and support a model in which effector proteins rely on Rabs as much as Rabs rely on effectors to achieve their correct steady state localizations.     

Enneanuclear Ni(II) complexes from the use of the flexible ligand 2-pyridinealdoxime: The nature of the inorganic anion does not affect the chemical and structural identity of the cationic cluster

The use of 2-pyridinealdoximate(−1) [(py)CHNO⁻] in nickel(II) chemistry has been further investigated. The synthetic investigation has led to two new salts of the very recently reported (in the form of its tetraperchlorate salt, 1) enneanuclear cation [Ni₉(μ₃-OH)₂(μ₂-OH)₂{μ₃-(py)CHNO}₄{μ₂-(py)CHNO}₆(μ₂-OH₂)₂(H₂O)₆]⁴⁺. The two new cationic clusters [Ni₉(OH)₄{(py)CHNO}₁₀(H₂O)₈](SCN)₂(OH)₂ · 9.91H₂O (2 · 9.91H₂O) and [Ni₉(OH)₄{(py)CHNO}₁₀(H₂O)₈]{N(CN)₂}₃(ClO₄) · 11.11H₂O (3 · 11.11H₂O) have been structurally characterized by single-crystal X-ray crystallography at 100 K. The nature of the inorganic anions (Cl⁻/SCN⁻,) present in the reaction mixtures does not affect the chemical and structural identity of the enneanuclear cation. Characteristic IR data are discussed in terms of the nature of bonding and the structures of the complexes. The variable-temperature magnetic susceptibility data of 1, which had also been obtained by our group, were simulated by means of a 3-J model, which is compared with the 2-J model reported for this cluster by Chaudhuri and co-workers [S. Khanra, T. Weyhermüller, E. Rentschler, P. Chaudhuri, Inorg. Chem. 44 (2005) 8176]. The ground-state total spin of the cluster is S_T = 1.     

A putative thiamine transport protein is a receptor for feline leukemia virus subgroup A

Feline leukemia virus (FeLV) is a horizontally transmitted virus that causes a variety of proliferative and immunosuppressive diseases in cats. There are four subgroups of FeLV, A, B, C, and T, each of which has a distinct receptor requirement. The receptors for all but the FeLV-A subgroup have been defined previously. Here, we report the identification of the cellular receptor for FeLV-A, which is the most transmissible form of FeLV. The receptor cDNA was isolated using a gene transfer approach, which involved introducing sequences from a feline cell line permissive to FeLV-A into a murine cell line that was not permissive. The feline cDNA identified by this method was approximately 3.5 kb, and included an open reading frame predicted to encode a protein of 490 amino acids. This feline cDNA conferred susceptibility to FeLV-A when reintroduced into nonpermissive cells, but it did not render these cells permissive to any other FeLV subgroup. Moreover, these cells specifically bound FeLV-A-pseudotyped virus particles, indicating that the cDNA encodes a binding receptor for FeLV-A. The feline cDNA shares approximately 93% amino acid sequence identity with the human thiamine transport protein 1 (THTR1). The human THTR1 receptor was also functional as a receptor for FeLV-A, albeit with reduced efficiency compared to the feline orthologue. On the basis of these data, which strongly suggest the feline protein is the orthologue of human THTR1, we have named the feline receptor feTHTR1. Identification of this receptor will allow more detailed studies of the early events in FeLV transmission and may provide insights into FeLV pathogenesis.     

First report of Neospora caninum abortion in a beef cow-calf herd from Andorra, Europe

Neospora caninum-associated abortion was diagnosed in a 7-mo gestational age beef cow fetus from Andorra. The fetus had a multifocal necrotizing encephalitis and nonpurulent multifocal myocarditis. The diagnosis was confirmed by demonstration of N. caninum DNA by polymerase chain reaction and tachyzoites by specific staining with N. caninum polyclonal antibodies in the fetal brain. The dam of the aborted fetus had serum N. caninum antibodies at the time of abortion but not 2 mo before abortion took place. This is the first report of N. caninum abortion in Andorra and the first confirmed N. caninum abortion in an acutely infected cow.     

ERK and p38 pathways regulate amino acid signalling

The ribosomal protein S6 kinase 1 (S6K1) is emerging as a common downstream target of signalling by hormones and nutrients such as insulin and amino acids. Here, we have investigated how amino acids signal through the S6K1 pathway. First, we found that a commercial anti-phospho-Thr389-S6K1 antibody detects an 80-90 kDa protein that is rapidly phosphorylated in response to amino acids. Unexpectedly, this phosphorylation was insensitive to both mTOR and PI-3 kinase inhibitors, and knockdown experiments showed that this protein was not S6K1. Looking for candidate targets of this phosphorylation, we found that amino acids stimulated phosphorylation of RSK and MSK kinases at residues that are homologous to Thr389 in S6K1. In turn, these phosphorylations required the activity of either p38 or ERK MAP kinases, which could compensate for each other. Moreover, we show that these MAP kinases are also needed for the amino acid-induced phosphorylation of S6K1 at Thr421/Ser424, as well as for that of S6K1 substrate, the S6 ribosomal protein. Consistent with these results, concomitant inhibition of p38 and ERK pathways also antagonised the well-known effects of amino acids on the process of autophagy. Altogether, these findings demonstrate a previously unknown role for MAP kinases in amino acid signalling.     

Hyperglycosylation and reduced GABA currents of mutated GABRB3 polypeptide in remitting childhood absence epilepsy

Childhood absence epilepsy (CAE) accounts for 10% to 12% of epilepsy in children under 16 years of age. We screened for mutations in the GABA(A) receptor (GABAR) beta 3 subunit gene (GABRB3) in 48 probands and families with remitting CAE. We found that four out of 48 families (8%) had mutations in GABRB3. One heterozygous missense mutation (P11S) in exon 1a segregated with four CAE-affected persons in one multiplex, two-generation Mexican family. P11S was also found in a singleton from Mexico. Another heterozygous missense mutation (S15F) was present in a singleton from Honduras. An exon 2 heterozygous missense mutation (G32R) was present in two CAE-affected persons and two persons affected with EEG-recorded spike and/or sharp wave in a two-generation Honduran family. All mutations were absent in 630 controls. We studied functions and possible pathogenicity by expressing mutations in HeLa cells with the use of Western blots and an in vitro translation and translocation system. Expression levels did not differ from those of controls, but all mutations showed hyperglycosylation in the in vitro translation and translocation system with canine microsomes. Functional analysis of human GABA(A) receptors (alpha 1 beta 3-v2 gamma 2S, alpha 1 beta 3-v2[P11S]gamma 2S, alpha 1 beta 3-v2[S15F]gamma 2S, and alpha 1 beta 3-v2[G32R]gamma 2S) transiently expressed in HEK293T cells with the use of rapid agonist application showed that each amino acid transversion in the beta 3-v2 subunit (P11S, S15F, and G32R) reduced GABA-evoked current density from whole cells. Mutated beta 3 subunit protein could thus cause absence seizures through a gain in glycosylation of mutated exon 1a and exon 2, affecting maturation and trafficking of GABAR from endoplasmic reticulum to cell surface and resulting in reduced GABA-evoked currents.     

Holocene palaeoenvironment in a former coastal lagoon of the arid south eastern Iberian Peninsula: salinization effects on δ<Superscript>15</Superscript>N

The palaeoenvironment of a former coastal lagoon in the south eastern Iberian Peninsula (San Rafael, Almeria, Spain) were inferred from one core analyzed for particulate organic matter content (POM) together with its C/N, δ¹³C, δ¹⁵N to depict the biogeochemical record from the Late Glacial to the Holocene. The results, complemented by previously reported pollen assemblages, indicate the appearance of a freshwater lagoon at 7300 b.p. (uncalibrated ¹⁴C age), its salinization at 6200 b.p. and its disappearance at 4400 b.p. The period of existence of the lagoon coincided with a period of wetter conditions as inferred from terrestrial vegetation. The lagoon’s salinization was not related to a decrease in precipitation but to a stronger maritime influence since there were no parallel changes in terrestrial vegetation. Salinization caused an increase in δ¹³C, associated with a higher relative presence of C₄ plants, and an increase in δ¹⁵N, due to a decrease in plant N demand. The late period of the lagoon, from about 5100 to 4400 b.p., shows a progressive drying and salinization not detected in isotopes but reflected in a decrease in POM, and in the pollen records. Increases in δ¹⁵N were related to increases in salinity within the lagoon, and are indicative of a more open N cycle, because the absence of changes in terrestrial vegetation rules out changes in the catchment area as the cause for changes in δ¹⁵N.