Polycystin-2 (TRPP2) Regulation by Ca2+ Is Effected and Diversified by Actin-Binding Proteins

Calcium regulation of Ca²⁺-permeable ion channels is an important mechanism in the control of cell function. Polycystin-2 (PC2, TRPP2), a member of the transient receptor potential superfamily, is a nonselective cation channel with Ca²⁺ permeability. The molecular mechanisms associated with PC2 regulation by Ca²⁺ remain ill-defined. We recently demonstrated that PC2 from human syncytiotrophoblast (PC2_hst) but not the in vitro translated protein (PC2_iv), functionally responds to changes in intracellular (cis) Ca²⁺. In this study we determined the regulatory effect(s) of Ca²⁺-sensitive and -insensitive actin-binding proteins (ABPs) on PC2_iv channel function in a lipid bilayer system. The actin-bundling protein α-actinin increased PC2_iv channel function in the presence of cis Ca²⁺, although instead was inhibitory in its absence. Conversely, filamin that shares actin-binding domains with α-actinin had a strong inhibitory effect on PC2_iv channel function in the presence, but no effect in the absence of cis Ca²⁺. Gelsolin stimulated PC2_iv channel function in the presence, but not the absence of cis Ca²⁺. In contrast, profilin that shares actin-binding domains with gelsolin, significantly increased PC2_iv channel function both in the presence and absence of Ca²⁺. The distinct effect(s) of the ABPs on PC2_iv channel function demonstrate that Ca²⁺ regulation of PC2 is actually mediated by direct interaction(s) with structural elements of the actin cytoskeleton. These data indicate that specific ABP-PC2 complexes would confer distinct Ca²⁺-sensitive properties to the channel providing functional diversity to the cytoskeletal control of transient receptor potential channel regulation.     

Alternaria alternata prevalence in cereal grains and soybean seeds from Entre Ríos, Argentina

A mycological survey was carried out at Entre Ríos province, Argentina, on sorghum grain, maize, rice, soybean seeds and on freshly harvested and stored wheat. The isolation frequencies and relative densities of species belonging to genera Alternaria, Aspergillus, Fusarium, Penicillium and other fungi were calculated. Alternaria alternata was the major fungal species isolated from sorghum, rice, soybean seeds and on freshly harvested wheat, and a low incidence of Fusarium species was observed on the same substrates. In maize the major fungal species isolated was Fusarium verticillioides. The high incidence levels of A. alternata observed,suggest that it may be necessary to determine, among other mycotoxins, if Alternaria toxins occur in these commodities.     

Bioavailability Studies of Stabilized Iron (II) Sulfate by Means of the Prophylactic-preventive Method

The bioavailability of stabilized ferrous sulfate was studied by means of the prophylactic-preventive test in rats. For comparative purposes, ferrous sulfate was used as reference standard. The test was performed in male weaned rats during 3 weeks, which were randomized into three groups of ten animals each. A control group received a basal diet of low iron content while the other groups received the same diet added with iron at a dose of 15 mg/kg as FeSO₄ 7H₂O and stabilized ferrous sulfate, respectively. Individual hemoglobin concentrations and weights were determined at the beginning and at the end of the study, and food intake was daily registered. Iron bioavailability (BioFe) of each source was calculated as the ratio between the amount of iron incorporated into hemoglobin during the treatment and the total iron intake per animal. A relative biological value was obtained as the ratio between the BioFe of stabilized ferrous sulfate and the reference standard given a value of 96%. Stabilized ferrous sulfate showed a high bioavailability, and when it is used to fortify dairy products as cheese and fluid milk in a dose of 15–20 mg of iron per kilogram, it behaved inertly in relation to the sensorial properties of the fortified food. These results suggest that this iron compound is a promising source to be use in food fortification.     

Acquisition of Visuomotor Abilities and Intellectual Quotient in Children Aged 4–10 Years: Relationship with Micronutrient Nutritional Status

Lethargy, poor attention, and the high rate and severity of infections in malnourished children affect their educational achievement. We therefore studied the association between visuomotor abilities and intelligence quotient (IQ) and their relationship with iron, zinc, and copper. A cross-sectional study was carried out on a sample of 89 healthy children (age range, 4-10 years). Evaluations of visuomotor ability and IQ were performed with the Developmental Test of Visual Motor Integration (VMI) and the Scale for Measurement of Intelligence for children aged 3-18 years, respectively. Nutritional status was assessed using anthropometry and biochemical assessments, which included serum ferritin, zinc and copper levels, and Hb. The sample was classified as having low or normal VMI scores: 47 children (52.8%, mean age 7 +/- 1.5 years) had low VMI, and 42 (47.2%, mean age 7 +/- 2.06 years) had normal VMI. There were no statistically significant differences in socioeconomic and cultural condition between both groups. We found significantly higher serum copper and ferritin levels in normal as compared to low VMI, but we did not find any differences with zinc. IQ was significantly higher in normal vs low VMI children. The fact that children with abnormal VMI presented low mean serum copper and ferritin concentrations could indicate that copper and iron deficiencies in this sample could be related with visuomotor abilities.     

Proteomic mapping of stimulus-specific signaling pathways involved in THP-1 cells exposed to Porphyromonas gingivalis or its purified components

Periodontitis is an inflammatory disease initiated by host-parasite interactions which contributes to connective tissue destruction and alveolar bone resorption. Porphyromonas gingivalis (P.g.), a black-pigmented Gram-negative anaerobic bacterium, is a major pathogen in the development and progression of periodontitis. To characterize the role that P. gingivalis and its cell surface components play in disease processes, we investigated the differential expression of proteins induced by live P.g., P.g. LPS, and P.g. FimA, using two-dimensional gel electrophoresis in combination with mass spectrometry. We have tested whether, at the level of protein expression, unique signaling pathways are differentially induced by the bacterial components P.g. LPS and P.g. FimA, as compared to live P.g. We found that P.g. LPS stimulation of THP-1 up-regulated the expression of a set of proteins compared to control: deoxyribonuclease, actin, carbonic anhydrase 2, alpha enolase, adenylyl cyclase-associated protein (CAP1), protein disulfide isomerase (PDI), glucose regulated protein (grp78), and 70-kDa heat shock protein (HSP70), whereas FimA treatment did not result in statistically significant changes to protein levels versus the control. Live P.g. stimulation resulted in 12 differentially expressed proteins: CAP1, tubulin beta-2 chain, ATP synthase beta chain, tubulin alpha-6 chain, PDI, vimentin, 60-kDa heat shock protein, and nucleolin were found to be up-regulated, while carbonic anhydrase II, beta-actin, and HSP70 were down-regulated relative to control. These differential changes by the bacteria and its components are interpreted as preferential signal pathway activation in host immune/inflammatory responses to P.g. infection.     

Constitutive expression of B7-1 on B cells uncovers autoimmunity toward the B cell compartment in the nonobese diabetic mouse

The NOD mouse is an invaluable model for the study of autoimmune diabetes. Furthermore, although less appreciated, NOD mice are susceptible to other autoimmune diseases that can be differentially manifested by altering the balance of T cell costimulatory pathways. In this study, we show that constitutively expressing B7-1 on B cells (NOD-B7-1B-transgenic mice) resulted in reduced insulitis and completely protected NOD mice from developing diabetes. Furthermore, B7-1 expression led to a dramatic reduction of the B cell compartment due to a selective deletion of follicular B cells in the spleen, whereas marginal zone B cells were largely unaffected. B cell depletion was dependent on B cell specificity, mediated by CD8(+) T cells, and occurred exclusively in the autoimmune-prone NOD background. Our results suggest that B cell deletion was a consequence of the specific activation of autoreactive T cells directed at peripheral self Ags presented by maturing B cells that expressed B7-1 costimulatory molecules. This study underscores the importance of B7 costimulatory molecules in controlling the amplitude and target of autoimmunity in genetically prone individuals and has important implications in the use of costimulatory pathway antagonists in the treatment of human autoimmune diseases.     

Disulfide bridges in the mesophilic triosephosphate isomerase from Giardia lamblia are related to oligomerization and activity

Triosephosphate isomerase from the mesophile Giardia lamblia (GlTIM) is the only known TIM with natural disulfide bridges. We previously found that oxidized and reduced thiol states of GlTIM are involved in the interconversion between native dimers and higher oligomeric species, and in the regulation of enzymatic activity. Here, we found that trophozoites and cysts have different oligomeric species of GlTIM and complexes of GlTIM with other proteins. Our data indicate that the internal milieu of G. lamblia is favorable for the formation of disulfide bonds. Enzyme mutants of the three most solvent exposed Cys of GlTIM (C202A, C222A, and C228A) were prepared to ascertain their contribution to oligomerization and activity. The data show that the establishment of a disulfide bridge between two C202 of two dimeric GlTIMs accounts for multimerization. In addition, we found that the establishment of an intramonomeric disulfide bond between C222 and C228 abolishes catalysis. Multimerization and inactivation are both reversed by reducing conditions. The 3D structure of the C202A GlTIM was solved at 2.1 A resolution, showing that the environment of the C202 is prone to hydrophobic interactions. Molecular dynamics of an in silico model of GlTIM when the intramonomeric disulfide bond is formed, showed that S216 is displaced 4.6 A from its original position, causing loss of hydrogen bonds with residues of the active-site loop. This suggests that this change perturb the conformational state that aligns the catalytic center with the substrate, inducing enzyme inactivation.