Genetic basis for tissue isozymes of glutamine synthetase in elasmobranchs

Tissue-specific isozymes of glutamine synthetase are present in elasmobranchs. A larger isozyme occurs in tissues in which the enzyme is localized in mitochondria (liver, kidney) whereas a smaller form occurs in tissues in which it is cytosolic (brain, spleen, etc.). The nucleotide sequence of spiny dogfish shark (Squalus acanthias) liver glutamine synthetase mRNA, derived from its cDNA, shows there are two in-frame initiation codons (AUG) at the N-terminus which will account for the size differences between the two isozymes. Initiation at the up-stream and down-stream sites would yield peptides of 45,406 and 41,869 mol. wts. representing the precursor of the mitochondrial isozyme and the cytosolic isozyme, respectively. The additional N-terminal 29 amino acids present in the mitochondrial isozyme precursor contains two putative cleavage sites based on the Arg-X-(Phe,Ile,Leu) motif. The predicted two-step processing would remove 14 of the 29 N-terminal amino acids. These 14 amino acids can be predicted to form a very strong amphipathic mitochondrial targeting signal. Their removal would yield a mature peptide of 43,680 mol. wt. The calculated mol. wts. based on the derived amino acid sequence are therefore in good agreement with previous estimates of an approximately 1.5–2-kDa difference between the M_rs of the mitochondrial and cytosolic isozymes. A model for the evolution of the mitochondrial targeting of glutamine synthetase in vertebrates is proposed. Correspondence to: J.W. CampbellThe nucleotide sequence reported will appear in GenBank under accession number U04617     

Hormonal regulation of sialic acid-binding (SAS) protein synthesis of rat uterus

Sialic acid binding proteins (SAS) of rat uteri have been found in all three stages of the estrous cycle. To study the control of synthesis of these proteins two different animal models were used I-immature female rats (25 d) where the hormones estradiol (E₂) and progesterone (P₄) were given separately and together, and II-adult female rats where hormone treatment commenced 14 days after ovariectomy. The data indicated that E₂ initiated the synthesis of SAS proteins in the immature animals, while P₄ could inhibit SAS synthesis, either given alone or together with E₂. However, prior priming of the rat with E₂ and subsequent administration of P₄ stimulated SAS protein synthesis.     

Cutting edge: macrophage migration inhibitory factor is necessary for progression of experimental autoimmune encephalomyelitis

Macrophage migration inhibitory factor (MIF) has been implicated in the pathogenesis of inflammatory and autoimmune diseases. The role of MIF in the progression of experimental autoimmune encephalomyelitis (EAE) was explored using MIF-/- mice. Wild-type mice showed a progressive disease course, whereas MIF-/- mice exhibited acute signs but no further progression of clinical disease. MIF-/- mice displayed markedly elevated corticosterone levels and significant decreases in the inflammatory cytokines TNF-alpha, IFN-gamma, IL-2, and IL-6 before, during, and after EAE onset. Taken together, these findings support that MIF is an important mediator of EAE progression through glucocorticoid antagonism and up-regulation of the inflammatory response.     

Antihypertensive Peptides Derived from Soy Protein by Fermentation

Soy protein is widely used as a nitrogen source in infant and adult formulations, both in an intact and hydrolyzed form. Here, the objective was to screen for maximum proteolytic activity in different strains of lactobacillus and use it for fermentation of soy protein to obtain Angiotensin converting-I-enzyme (ACE I) inhibitory peptides for its use as a nutraceutical. Based on the proteolytic activity, Lactobacillus casei spp. pseudoplantarum was selected. The two ACE inhibitory peptide fractions F2 and F3 were isolated having IC₅₀ values of 17 ± 0.63 and 30 ± 0.13 μg/ml respectively. The N-terminal sequence of peptide (F2) was determined to be Leu-Ile-Val-Thr-Gln (LIVTQ). The peptide analogues of LIVTQ were synthesized to study the effect of individual residues on ACE enzyme. LIVTQ and LIVT peptides show inhibition against ACE enzyme having an IC₅₀ value of 0.087 and 0.110 μM respectively. Our results depict that glutamine (Q) and threonine (T) residues have an important role in ACE inhibition.     

Interactions between immunity,proliferation and molecular subtype in breast cancer prognosis

Background

Gene expression signatures indicative of tumor proliferative capacity and tumor-immune cell interactions have emerged as principal biology-driven predictors of breast cancer outcomes. How these signatures relate to one another in biological and prognostic contexts remains to be clarified.

Results

To investigate the relationship between proliferation and immune gene signatures, we analyzed an integrated dataset of 1,954 clinically annotated breast tumor expression profiles randomized into training and test sets to allow two-way discovery and validation of gene-survival associations. Hierarchical clustering revealed a large cluster of distant metastasis-free survival-associated genes with known immunological functions that further partitioned into three distinct immune metagenes likely reflecting B cells and/or plasma cells; T cells and natural killer cells; and monocytes and/or dendritic cells. A proliferation metagene allowed stratification of cases into proliferation tertiles. The prognostic strength of these metagenes was largely restricted to tumors within the highest proliferation tertile, though intrinsic subtype-specific differences were observed in the intermediate and low proliferation tertiles. In highly proliferative tumors, high tertile immune metagene expression equated with markedly reduced risk of metastasis whereas tumors with low tertile expression of any one of the three immune metagenes were associated with poor outcome despite higher expression of the other two metagenes.

Conclusions

These findings suggest that a productive interplay among multiple immune cell types at the tumor site promotes long-term anti-metastatic immunity in a proliferation-dependent manner. The emergence of a subset of effective immune responders among highly proliferative tumors has novel prognostic ramifications.     

Visceral adipose inflammation in obesity is associated with critical alterations in tregulatory cell numbers

Background

The development of insulin resistance (IR) in mouse models of obesity and type 2 diabetes mellitus (DM) is characterized by progressive accumulation of inflammatory macrophages and subpopulations of T cells in the visceral adipose. Regulatory T cells (Tregs) may play a critical role in modulating tissue inflammation via their interactions with both adaptive and innate immune mechanisms. We hypothesized that an imbalance in Tregs is a critical determinant of adipose inflammation and investigated the role of Tregs in IR/obesity through coordinated studies in mice and humans.

Methods and Findings

Foxp3-green fluorescent protein (GFP) “knock-in” mice were randomized to a high-fat diet intervention for a duration of 12 weeks to induce DIO/IR. Morbidly obese humans without overt type 2 DM (n = 13) and lean controls (n = 7) were recruited prospectively for assessment of visceral adipose inflammation. DIO resulted in increased CD3⁺CD4⁺, and CD3⁺CD8⁺ cells in visceral adipose with a striking decrease in visceral adipose Tregs. Treg numbers in visceral adipose inversely correlated with CD11b⁺CD11c⁺ adipose tissue macrophages (ATMs). Splenic Treg numbers were increased with up-regulation of homing receptors CXCR3 and CCR7 and marker of activation CD44. In-vitro differentiation assays showed an inhibition of Treg differentiation in response to conditioned media from inflammatory macrophages. Human visceral adipose in morbid obesity was characterized by an increase in CD11c⁺ ATMs and a decrease in foxp3 expression.

Conclusions

Our experiments indicate that obesity in mice and humans results in adipose Treg depletion. These changes appear to occur via reduced local differentiation rather than impaired homing. Our findings implicate a role for Tregs as determinants of adipose inflammation.     

Epigenetic regulation of transcription by RNA polymerase III

Chromatin participates actively in all DNA transactions and all phenomena directly under the influence of chromatin are explained by epigenetic mechanisms. The genes transcribed by RNA polymerase (pol) III are generally found in regions free of nucleosomes, the structural units of chromatin. Yet, histone modifications and positions of nucleosomes in the gene flanking regions have been reported to show direct correlation with activity status of these genes. Gene-specific as well as genome-wide studies have also revealed association of several epigenetic components with pol III-transcribed genes. This review presents a summary of the research in past many years, which have gathered enough evidence to conclude that pol III-transcribed genes are important components of an epigenome.