The human endonexin II (ENX2) gene is located at 4q28----q32

A relatively recently identified family of structurally similar Ca2(+)-dependent phospholipid binding proteins is called the annexin gene family. At least seven genes are known, although their exact functions are unclear. The endonexin II gene (ENX2), one member of the gene family, is assigned to 4q28----q32 using both Southern transfer analysis of human x rodent somatic cell hybrid DNAs and in situ chromosome hybridization. One of the lipocortin II genes, another annexin, had previously been assigned to the long arm of chromosome 4.     

Characterization and cDNA cloning of phospholipase C-gamma, a major substrate for heparin-binding growth factor 1 (acidic fibroblast growth factor)-activated tyrosine kinase.

Heparin-binding growth factors (HBGFs) bind to high-affinity cell surface receptors which possess intrinsic tyrosine kinase activity. A Mr 150,000 protein phosphorylated on tyrosine in response to class 1 HBGF (HBGF-1) was purified and partially sequenced. On the basis of this sequence, cDNA clones were isolated from a human endothelial cell library and identified as encoding phospholipase C-gamma. Phosphorylation of phospholipase C-gamma in intact cells treated with HBGF-1 was directly demonstrated by using antiphospholipase C-gamma antibodies. Thus, HBGF-1 joins epidermal growth factor and platelet-derived growth factor, whose receptor activation leads to tyrosine phosphorylation and probable activation of phospholipase C-gamma.     

TAP1 and TAP2 transporter genes and predisposition to insulin dependent diabetes mellitus.

Genetic control of insulin dependent diabetes mellitus (IDDM) is mainly dependent on HLA genes in the major histocompatibility complex (MHC). The participation of TAP1 and TAP2 genes, located in the MHC region and coding for antigenic peptide transporters, was investigated in 116 IDDM patients and 98 normal controls using oligotyping after DNA amplification. The TAP2-B allele had a dominant protective effect, additive to that of the DR2 haplotype but antagonist to the susceptibility associated with the DR3 and/or DR4 haplotypes. The TAP2-A allele, in the homozygous state, had a predisposing effect. TAP1 allelic distribution did not differ among IDDM patients and controls. These data argue in favour of the role of peptide transporter gene in diabetogenesis.     

Ligand-induced transphosphorylation between different FGF receptors.

Recent evidence shows that different fibroblast growth factors (FGF) bind with similar high affinities to two FGF receptors (FGFR) called flg and bek. In order to explore the mechanism of FGFR tyrosine autophosphorylation, we have generated cell lines which co-express a kinase-negative mutant of FGFR and an active form of FGFR. The following transfected NIH 3T3 cells were generated: (i) cells which express a shorter truncated form of bek (two Ig domains) together with a kinase-negative mutant of full length bek (bek K517A), (ii) cells which express wild-type bek together with kinase-negative flg (flg K514A) and (iii) cells co-expressing wild-type flg together with bek K517A. Immunoprecipitations with either bek-or flg-specific antisera followed by immunoblotting indicated that the double transfectants express the desired receptor species. The addition of acidic FGF (aFGF) to the various cell lines followed by immunoprecipitation with anti-FGFR antibodies and immunoblotting with anti-phosphotyrosine specific antibodies indicated that aFGF induces tyrosine phosphorylation of the kinase-negative FGFR mutants. These results show that tyrosine autophosphorylation of the kinase-negative FGFR is mediated by a transphosphorylation mechanism and that both homologous (bek----bek) and heterologous (bek----flg and flg----bek) transphosphorylation occurs in living cells. Recent evidence shows that tyrosine autophosphorylation of receptors with tyrosine kinase activities is essential for mediating interactions with signaling molecules. Therefore, heterologous transphosphorylation could amplify the response of cells to various forms of FGFs and their cognate receptors.     

Oxygen consumption and body temperature in yellow-bellied marmot populations from montane-mesic and lowland-xeric environments

Summary Yellow-bellied marmots characteristically live in montane-mesic environments, but in several areas in western North America, this species extended its range into lowland-xeric habitats. Body mass was significantly smaller in the lowland-xeric population from eastern Washington at 393 m than in the montane-mesic population from western Colorado at 2900 m. Oxygen consumption of marmots from montane-mesic and lowland-xeric environments was signiflcantly affected by ambient temperature (T_A) water regimen, population, and a population x water regimen x temperature interaction. Lowland-xeric animals had a higher metabolic rate at low T_As, but a lower metabolic rate at higher T_As than the montane-mesic aminals. Oxygen consumption was lower on a restricted-water regimen than on ad libitum water in both populations. Coefficients relating oxygen consumption to body mass were affected by T_A, water regimen, and population. These intraspecific coefficients are larger than the interspecific coefficients for all mammals. Body temperature (T_B) was affected significantly by T_A, water regimen, and population. T_A body mass, and a population x water regimen interaction significantly affected conductance. Conductance generally was higher in the lowland-xeric than in the montane-mesic marmots. Both populations increased conductance at high T_A, but the lowland-xeric population dissipated a much higher proportion of the heat by evaporative water loss (EWL) than did the montane-mesic population. Metabolic water production exceeded or equaled EWL at 5–20°C. Smaller body size, reduced metabolism at high T_A, and increased EWL at high T_A characterized the lowland-xeric population.Metabolic rates of yellow-bellied marmots were higher than predicted from body size during the reproductive season but decreased to 67% of that predicted from the Kleiber curve by late summer. Marmots minimize thermoregulatory costs by concentrating activity at times when the microclimate is favorable, by tolerating hyperthermia at high T_A in the field, and by having a conductance lower than that predicted from body size.Abbreviations DHC dry-heat conductance - EHL evaporative heat loss - EWL evaporative water loss - HP heat produced - T _A ambient temperature - T _n body temperature - M body mass     

Identification of six novel autophosphorylation sites on fibroblast growth factor receptor 1 and elucidation of their importance in receptor activation and signal transduction.

Fibroblast growth factor receptor (FGFR) activation leads to receptor autophosphorylation and increased tyrosine phosphorylation of several intra cellular proteins. We have previously shown that autophosphorylated tyrosine 766 in FGFR1 serves as a binding site for one of the SH2 domains of phospholipase Cy and couples FGFR1 to phosphatidylinositol hydrolysis in several cell types. In this report, we describe the identification of six additional autophosphorylation sites (Y-463, Y-583, Y-585, Y-653, Y-654 and Y-730) on FGFR1. We demonstrate that autophosphorylation on tyrosines 653 and 654 is important for activation of tyrosine kinase activity of FGFR1 and is therefore essential for FGFR1-mediated biological responses. In contrast, autophosphorylation of the remaining four tyrosines is dispensable for FGFR1-mediated mitogen-activated protein kinase activation and mitogenic signaling in L-6 cells as well as neuronal differentiation of PC12 cells. Interestingly, both the wild-type and a mutant FGFR1 (FGFR1-4F) are able to phosphorylate Shc and an unidentified Grb2-associated phosphoprotein of 90 kDa (pp90). Binding of the Grb2/Sos complex to phosphorylated Shc and pp90 may therefore be the key link between FGFR1 and the Ras signaling pathway, mito-genesis, and neuronal differentiation.     

Effect of heparin on the binding affinity of acidic FGF for the cloned human FGF receptors, flg and bek.

Heparin potentiates the mitogenic activity of acidic fibroblast growth factor (aFGF) by 20-100 fold but mechanisms detailing this potentiation have not yet been fully elucidated. We report that heparin increases the binding affinity of aFGF for the two cloned and overexpressed human FGF receptors, flg and bek, by 2-3 fold. This increase in binding affinity, together with previous data demonstrating a 3-5 fold increase in the stability of aFGF, are likely to account for a significant portion of heparin's potentiation of aFGF activity observed in biological assay systems.     

The gene for human acidic fibroblast growth factor encodes two upstream exons alternatively spliced to the first coding exon

We have isolated two cDNA clones encoding human acidic fibroblast growth factor (aFGF) which represent the utilization of alternative upstream exons in aFGF mRNA. Isolation and sequence analysis of genomic clones spanning the first coding exon and each of the upstream sequences confirms that the divergent 5' sequences are separate exons, spliced alternatively to the first coding exon 34 nucleotides upstream of the initiator AUG codon. Restriction mapping of the genomic clones provides a minimum size estimate of 45 kilobase pairs for the aFGF locus.     

Increased Carotid Intima-Media Thickness and Reduced Distensibility in Human Class III Obesity: Independent and Differential Influences of Adiposity and Blood Pressure on the Vasculature

Carotid intima-media-thickness (cIMT) and carotid distensibility (distensibility), structural and functional properties of carotid arteries respectively, are early markers, as well as strong predictors of cardiovascular disease (CVD). The characteristic of these two parameters in individuals with BMI>40.0 kg/m² (Class III obesity), however, are largely unknown. The present study was designed to document cIMT and distensibility in this population and to relate these to other factors with established association with CVD in obesity. The study included 96 subjects (65 with BMI>40.0 kg/m² and 31, age- and gender-matched, with BMI of 18.5 to 30.0 kg/m²). cIMT and distensibility were measured by non-invasive high resolution ultrasonography, circulatory CD133⁺/KDR⁺ angiogenic cells and endothelial microparticles (EMP) by flow cytometry, and plasma levels of adipokines, growth factors and cytokines by Luminex immunoassay kits. The study results demonstrated increased cIMT (0.62±0.11 mm vs. 0.54±0.08 mm, P = 0.0002) and reduced distensibility (22.52±10.79 10⁻³kpa⁻¹ vs. 29.91±12.37 10⁻³kpa⁻¹, P<0.05) in individuals with BMI>40.0 kg/m². Both cIMT and distensibility were significantly associated with traditional CVD risk factors, adiposity/adipokines and inflammatory markers but had no association with circulating angiogenic cells. We also demonstrated, for the first time, elevated plasma EMP levels in individuals with BMI>40.0 kg/m². In conclusion, cIMT is increased and distensibility reduced in Class III obesity with the changes predominantly related to conventional CVD risk factors present in this condition, demonstrating that both cIMT and distensibility remain as CVD markers in Class III obesity.