Specific glucocorticoid binding in human uterine tissues, placenta and fetal membranes

The binding of [3H]dexamethasone to cytosol fractions of human myometrium, endometrium, decidua, chorion, amnion and placenta has been studied. All tissues examined contained high affinity, low capacity binding sites with high specificity for glucocorticoids. Maximum specific binding of [3H]dexamethasone was reached after about 10 h at 0-4 degrees C and remained stable for at least the next 12 h. Sucrose density gradient analysis showed that the binding macromolecules sedimented at 7.9 S in hypotonic solutions and at 4.35 in solutions containing 0.4 M KCl. In the presence of sodium molybdate, the sedimentation coefficients shifted both in the absence and presence of 0.4 M KCl to 8.9 and 5.7 S, respectively. The apparent equilibrium dissociation constants (Kd) of the glucocorticoid binding sites were similar in most tissues, ranging between 1 and 6 nM, with the exception of the placenta in which the binding sites showed a higher Kd (13-22 nM). In all tissues studied, the binding affinities were similar in nonpregnant and pregnant patients and in patients at different stages of pregnancy or in labor. The concentration of the binding sites in the different tissues ranged from 11 to 268 fmol/mg protein, higher concentrations being found in myometrium, placenta and amnion and lower concentrations found in endometrium, chorion and decidua. The number of binding sites was higher in the myometrium of nonpregnant than pregnant women, but was similar in the myometrium of women at term pregnancy before or during labor. In the placenta, the number of binding sites increased significantly from early pregnancy to midpregnancy, while in chorion, amnion and decidua the number of binding sites did not change during pregnancy. It is concluded that human uterine tissues, placenta and fetal membranes contain specific binding sites with properties characteristic of glucocorticoid receptors suggesting that these tissues may respond directly to glucocorticoids.     

Pseudohypoparathyroidism type Ia: two new heterozygous frameshift mutations in exons 5 and 10 of the Gsα gene

Pseudohypoparathyroidism type Ia (PHP-Ia) is a hereditary disease characterized by resistance to PTH and other hormones that act via cAMP. Patients have deficient activity of Gs, the subunit of the G protein, which couples hormone receptors to stimulation of adenylate cyclase. We describe two new mutations discovered in two sporadic patients with PHP-Ia. Using genomic DNA, we have amplified exons 2–13 of the Gs gene (GNAS1) by PCR, and sequenced the resulting products. Both patients had Albright's hereditary osteodystrophy, resistance to multiple hormones, and deficient Gs activity. In the first patient, a deletion of a C in exon 5 at codon 115 was found. In the second patient, an insertion of a C in exon 10 at codon 267 was detected. Both these heterozygous mutations cause frameshift, and predict decreased production of Gs. This report adds two new Gs mutations to the known ten mutations recently described.     

Neuraminidase-Mediated,NKp46-Dependent Immune-Evasion Mechanism of Influenza Viruses

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Deletion of PsbM in tobacco alters the QB site properties and the electron flow within photosystem II

Photosystem II, the oxygen-evolving complex of photosynthetic organisms, includes an intriguingly large number of low molecular weight polypeptides, including PsbM. Here we describe the first knock-out of psbM using a transplastomic, reverse genetics approach in a higher plant. Homoplastomic Delta psbM plants exhibit photoautotrophic growth. Biochemical, biophysical, and immunological analyses demonstrate that PsbM is not required for biogenesis of higher order photosystem II complexes. However, photosystem II is highly light-sensitive, and its activity is significantly decreased in Delta psbM, whereas kinetics of plastid protein synthesis, reassembly of photosystem II, and recovery of its activity are comparable with the wild type. Unlike wild type, phosphorylation of the reaction center proteins D1 and D2 is severely reduced, whereas the redox-controlled phosphorylation of photosystem II light-harvesting complex is reversely regulated in Delta psbM plants because of accumulation of reduced plastoquinone in the dark and a limited photosystem II-mediated electron transport in the light. Charge recombination in Delta psbM measured by thermoluminescence oscillations significantly differs from the 2/6 patterns in the wild type. A simulation program of thermoluminescence oscillations indicates a higher Q(B)/Q(-)(B) ratio in dark-adapted mutant thylakoids relative to the wild type. The interaction of the Q(A)/Q(B) sites estimated by shifts in the maximal thermoluminescence emission temperature of the Q band, induced by binding of different herbicides to the Q(B) site, is changed indicating alteration of the activation energy for back electron flow. We conclude that PsbM is primarily involved in the interaction of the redox components important for the electron flow within, outward, and backward to photosystem II.     

Liprin beta 1, a member of the family of LAR transmembrane tyrosine phosphatase-interacting proteins, is a new target for the metastasis-associated protein S100A4 (Mts1)

Metastasis-associated protein S100A4 (Mts1) induces invasiveness of primary tumors and promotes metastasis. S100A4 belongs to the family of small calcium-binding S100 proteins that are involved in different cellular processes as transducers of calcium signal. S100A4 modulates properties of tumor cells via interaction with its intracellular targets, heavy chain of non-muscle myosin and p53. Here we report identification of a new molecular target of the S100A4 protein, liprin beta1. Liprin beta1 belongs to the family of leukocyte common antigen-related (LAR) transmembrane tyrosine phosphatase-interacting proteins that may regulate LAR protein properties via interaction with another member of the family, liprin alpha1. We showed by the immunoprecipitation analysis that S100A4 interacts specifically with liprin beta1 in vivo. Immunofluorescence staining demonstrated the co-localization of S100A4 and liprin beta1 in the cytoplasm and particularly at the protrusion sites of the plasma membrane. We mapped the S100A4 binding site at the C terminus of the liprin beta1 molecule between amino acid residues 938 and 1005. The S100A4-binding region contains two putative phosphorylation sites by protein kinase C and protein kinase CK2. S100A4-liprin beta1 interaction resulted in the inhibition of liprin beta1 phosphorylation by both kinases in vitro.     

Increased glucose uptake promotes oxidative stress and PKC-delta activation in adipocytes of obese,insulin-resistant mice

Increased oxidative stress is believed to be one of the mechanisms responsible for hyperglycemia-induced tissue damage and diabetic complications. In these studies, we undertook to characterize glucose uptake and oxidative stress in adipocytes of type 2 diabetic animals and to determine whether these promote the activation of PKC-delta. The adipocytes used were isolated either from C57Bl/6J mice that were raised on a high-fat diet (HF) and developed obesity and insulin resistance or from control animals. Basal glucose uptake significantly increased (8-fold) in HF adipocytes, and this was accompanied with upregulation of GLUT1 expression levels. Insulin-induced glucose uptake was inhibited in HF adipocytes and GLUT4 content reduced by 20% in these adipocytes. Reactive oxygen species (ROS) increased twofold in HF adipocytes compared with control adipocytes and were largely reduced with decreased glucose concentrations. At zero glucose, ROS levels were reduced to the normal levels seen in control adipocytes. The activity of PKC-delta increased twofold in HF adipocytes compared with control adipocytes and was further activated by H2O2. Moreover, PKC-delta activity was inhibited in HF adipocytes either by glucose deprivation or by treatment with the antioxidant N-acetyl-l-cysteine. In summary, we propose that increased glucose intake in HF adipocytes increases oxidative stress, which in turn promotes the activation of PKC-delta. These consequential events may be responsible, at least in part, for development of HF diet-induced insulin resistance in the fat tissue.     

Intracellular cysteine residues in the tail of MHC class I proteins are crucial for extracellular recognition by leukocyte Ig-like receptor 1

The activity of NK cells is regulated by activating receptors that recognize mainly stress-induced ligands and by inhibitory receptors that recognize mostly MHC class I proteins on target cells. Comparing the cytoplasmic tail sequences of various MHC class I proteins revealed the presence of unique cysteine residues in some of the MHC class I molecules which are absent in others. To study the role of these unique cysteines, we performed site specific mutagenesis, generating MHC class I molecules lacking these cysteines, and demonstrated that their expression on the cell surface was impaired. Surprisingly, we demonstrated that these cysteines are crucial for the surface binding of the leukocyte Ig-like receptor 1 inhibitory receptor to the MHC class I proteins, but not for the binding of the KIR2DL1 inhibitory receptor. In addition, we demonstrated that the cysteine residues in the cytoplasmic tail of MHC class I proteins are crucial for their egress from the endoplasmic reticulum and for their palmitoylation, thus probably affecting their expression on the cell surface. Finally, we show that the cysteine residues are important for proper extracellular conformation. Thus, although the interaction between leukocyte Ig-like receptor 1 and MHC class I proteins is formed between two extracellular surfaces, the intracellular components of MHC class I proteins play a crucial role in this recognition.