Role of the tumor suppressor IQGAP2 in metabolic homeostasis: possible link between diabetes and cancer

Deficiency of IQGAP2, a scaffolding protein expressed primarily in liver leads to rearrangements of hepatic protein compartmentalization and altered regulation of enzyme functions predisposing development of hepatocellular carcinoma and diabetes. Employing a systems approach with proteomics, metabolomics and fluxes characterizations, we examined the effects of IQGAP2 deficient proteomic changes on cellular metabolism and the overall metabolic phenotype. Iqgap2 ^?/?mice demonstrated metabolic inflexibility, fasting hyperglycemia and obesity. Such phenotypic characteristics were associated with aberrant hepatic regulations of glycolysis/gluconeogenesis, glycogenolysis, lipid homeostasis and futile cycling corroborated with corresponding proteomic changes in cytosolic and mitochondrial compartments. IQGAP2 deficiency also led to truncated TCA-cycle, increased anaplerosis, increased supply of acetyl-CoA for de novo lipogenesis, and increased mitochondrial methyl-donor metabolism necessary for nucleotides synthesis. Our results suggest that changes in metabolic networks in IQGAP2 deficiency create a hepatic environment of a ‘pre-diabetic’ phenotype and a predisposition to non-alcoholic fatty liver disease which has been linked to the development of hepatocellular carcinoma.     

Regulation and dysregulation of immunoglobulin E: a molecular and clinical perspective

Background

Altered levels of Immunoglobulin E (IgE) represent a dysregulation of IgE synthesis and may be seen in a variety of immunological disorders. The object of this review is to summarize the historical and molecular aspects of IgE synthesis and the disorders associated with dysregulation of IgE production.

Methods

Articles published in Medline/PubMed were searched with the keyword Immunoglobulin E and specific terms such as class switch recombination, deficiency and/or specific disease conditions (atopy, neoplasia, renal disease, myeloma, etc.). The selected papers included reviews, case reports, retrospective reviews and molecular mechanisms. Studies involving both sexes and all ages were included in the analysis.

Results

Both very low and elevated levels of IgE may be seen in clinical practice. Major advancements have been made in our understanding of the molecular basis of IgE class switching including roles for T cells, cytokines and T regulatory (or Treg) cells in this process. Dysregulation of this process may result in either elevated IgE levels or IgE deficiency.

Conclusion

Evaluation of a patient with elevated IgE must involve a detailed differential diagnosis and consideration of various immunological and non-immunological disorders. The use of appropriate tests will allow the correct diagnosis to be made. This can often assist in the development of tailored treatments.     

Culture surface and exogenous putrescine-altered shoot growth pattern in mannitol- and cadmium chloride-pretreated callus of <Emphasis Type="BoldItalic">Cymbidium</Emphasis> Via del Playa “Yvonne”

Evidence for the link between the surface of culture medium and abnormal shoot formation in the presence of exogenous putrescine is presented. Little is known about the role of putrescine in rapid shoot regeneration in the callus of orchids pretreated with mannitol and cadmium chloride (CdCl₂). Ultrastructural analysis of putrescine-altered CdCl₂- and mannitol-treated callus after 4 wk of culture showed the presence of numerous oil droplets, rough endoplasmic reticulum, and dictyosomes. Callus pretreated with mannitol and CdCl₂ but without exogenous putrescine showed the presence of amyloplasts, condensed mitochondria, and active vacuole within 12 h of pretreatment. This study not only establishes a new method to achieve rapid regeneration of Cymbidium callus but also describes different types of shoots on the basis of its contact with the surface of the culture medium. Histologically, two types of cells in the apical meristem are defined. One type of cells has compromised volume which was lost upon division and is represented by small deeply stained cells of the shoots regenerated from the upper portion of the callus and is considered normal. The other type is represented by highly vacuolated and less deeply stained cells of the shoots regenerated from the lower portion of the callus in contact with the medium and is considered abnormal in this study. To avoid such abnormalities, frequent subculture of callus halves which were obtained by a median transverse cut before the regenerants (PLBs) were converted to shoots is recommended. This new methodology was successful in achieving rapid regeneration of uniform shoots from callus.     

Genomic variation in the mitochondrially encoded cytochrome b (MT-CYB) and 16S rRNA (MT-RNR2) genes: characterization of eight endangered Pecoran species

In an effort to develop species-specific identification markers, we examined genetic variants and molecular signatures within genes encoding mitochondrial cytochrome b and 16S rRNA in eight endangered Pecoran species endemic to the Indian peninsula. Our results revealed that the cytochrome b gene exhibited higher sequence diversity than the 16S rRNA gene, both between and within species. However, the 16S rRNA gene harboured a larger number of species-specific mutation sites compared with the cytochrome b gene, suggesting that it could be useful for species identification. Indeed, we successfully used 'forensically informative nucleotide sequencing' (FINS) analysis of the 16S rRNA gene to identify two previously unknown biological specimens.     

The multifaceted roles of neutrophil gelatinase associated lipocalin (NGAL) in inflammation and cancer

Neutrophil gelatinase associated lipocalin (NGAL), also known as oncogene 24p3, uterocalin, siderocalin or lipocalin 2, is a 24kDa secreted glycoprotein originally purified from a culture of mouse kidney cells infected with simian virus 40 (SV-40). Subsequent investigations have revealed that it is a member of the lipocalin family of proteins that transport small, hydrophobic ligands. Since then, NGAL expression has been reported in several normal tissues where it serves to provide protection against bacterial infection and modulate oxidative stress. Its expression is also dysregulated in several benign and malignant diseases. Its small size, secreted nature and relative stability have led to it being investigated as a diagnostic and prognostic biomarker in numerous diseases including inflammation and cancer. Functional studies, conducted primarily on lipocalin 2 (Lcn2), the mouse homologue of human NGAL have revealed that Lcn2 has a strong affinity for iron complexed to both bacterial siderophores (iron-binding proteins) and certain human proteins like norepinephrine. By sequestering iron-laden siderophores, Lcn2 deprives bacteria of a vital nutrient and thus inhibits their growth (bacteriostatic effect). In malignant cells, its proposed functions range from inhibiting apoptosis (in thyroid cancer cells), invasion and angiogenesis (in pancreatic cancer) to increasing proliferation and metastasis (in breast and colon cancer). Ectopic expression of Lcn2 also promotes BCR-ABL induced chronic myelogenous leukemia in murine models. By transporting iron into and out of the cell, NGAL also regulates iron responsive genes. Further, it stabilizes the proteolytic enzyme matrix metalloprotease-9 (MMP-9) by forming a complex with it, and thereby prevents its autodegradation. The factors regulating NGAL expression are numerous and range from pro-inflammatory cytokines like interleukins, tumor necrosis factor-α and interferons to vitamins like retinoic acid. The purpose of this review article is to examine the expression, structure, regulation and biological role of NGAL and critically assess its potential as a novel diagnostic and prognostic marker in both benign and malignant human diseases.     

USP2a protein deubiquitinates and stabilizes the circadian protein CRY1 in response to inflammatory signals

The mammalian circadian clock coordinates various physiological activities with environmental cues to achieve optimal adaptation. The clock manifests oscillations of key clock proteins, which are under dynamic control at multiple post-translational levels. As a major post-translational regulator, the ubiquitination-dependent proteasome degradation system is counterbalanced by a large group of deubiquitin proteases with distinct substrate preference. Until now, whether deubiquitination by ubiquitin-specific proteases can regulate the clock protein stability and circadian pathways remains largely unclear. The mammalian clock protein, cryptochrome 1 (CRY1), is degraded via the FBXL3-mediated ubiquitination pathway, suggesting that it is also likely to be targeted by the deubiquitination pathway. Here, we identified that USP2a, a circadian-controlled deubiquitinating enzyme, interacts with CRY1 and enhances its protein stability via deubiquitination upon serum shock. Depletion of Usp2a by shRNA greatly enhances the ubiquitination of CRY1 and dampens the oscillation amplitude of the CRY1 protein during a circadian cycle. By stabilizing the CRY1 protein, USP2a represses the Per2 promoter activity as well as the endogenous Per2 gene expression. We also demonstrated that USP2a-dependent deubiquitination and stabilization of the CRY1 protein occur in the mouse liver. Interestingly, the pro-inflammatory cytokine, TNF-α, increases the CRY1 protein level and inhibits circadian gene expression in a USP2a-dependent fashion. Therefore, USP2a potentially mediates circadian disruption by suppressing the CRY1 degradation during inflammation.