A specific DIF binding protein in Dictyostelium

Differentiation Inducing Factor (DIF-1), a small chlorinated organic molecule which is produced during Dictyostelium development, is believed to be the morphogen that controls the stalk-specific pathway of differentiation. We describe the identification and characterization of a protease-sensitive activity from cell lysates which binds tritiated DIF-1 with the properties expected of a DIF receptor. Scatchard and linear subtraction plots show a single class of binding sites, of high affinity (Kd = 1.8 nM) and low abundance (1100 sites/cell). The activity elutes from heparin-agarose as a single peak. Various DIF-1 analogues compete for binding in proportion to their activities in a stalk cell differentiation bioassay. The amount of binding activity is developmentally regulated, peaking shortly before the appearance of the prestalk-prespore pattern and before the developmental rise in DIF concentration; the rise occurs at the same time that prestalk-specific genes become DIF inducible. Addition of cyclic AMP to aggregated cells, which induces post-aggregative gene expression in general, also induces the binding activity.     

A polymorphic, prespore-specific cell surface glycoprotein is present in the extracellular matrix of Dictyostelium discoideum.

Polymorphisms of a major developmentally regulated prespore-specific protein (PsA) in Dictyostelium discoideum slugs are described. These polymorphisms allowed discrimination between PsA (found on the cell surface and in the extracellular matrix) and a similar extracellular but nonpolymorphic protein, ShA. The two proteins were also distinguished by their differing reactivities with a range of monoclonal antibodies and by their sensitivity to release from the sheath with cellulase. The results are discussed in terms of the molecular and genetic relationships between the cell surface and the extracellular matrix during development.     

The mif gene is transcriptionally regulated by glucose in insulin-secreting cells

We have established that focal adhesion kinase (FAK)-transfected HL-60 (HL-60/FAK) cells were highly resistant to hydrogen peroxide and etoposide-induced apoptosis compared to vector-transfected cells. Mutagenesis study revealed that Y397 is required for anti-apoptotic activity in HL-60/FAK, since Y397F-mutated FAK (397FAK) lost anti-apoptotic function. Assuming that 397FAK functions as a dominant negative FAK, we introduced 397FAK cDNA into a human glioma cell line, T98G, using an adenoviral vector. We found that 397FAK induced marked apoptosis with significant FAK degradation. As PI3-kinase-Akt survival pathway was constitutively activated in T98G cells, we hypothesized that this pathway was shut off by 397FAK gene transfection. As expected, activation of PI3-kinase-Akt survival pathway was decreased by the 397FAK gene transfection. 397FAK activated mainly caspase-6 which induced degradation of transfected FAK as well as endogenous FAK. These results indicated that 397FAK induces apoptosis in T98G cells, by interrupting signals of FAK leading to the survival pathway in T98G glioma cells.     

盘基网柄菌中分化诱导因子信号与细胞命运决定

对盘基网柄菌发育过程中分化诱导因子(DIF)的作用及其机制进行了综述,包括DIF对盘基网柄菌前柄细胞、柄细胞分化的作用以及DIF的生物合成、DIF的诱导、降解失活、DIF对细胞命运和细胞比例的调节及其作用机制等。     

The human PER1 gene is transcriptionally regulated by multiple signaling pathways

The mammalian period (Per) genes are components of the circadian clock and appear to be regulated via an autoregulatory feedback loop. Here we show that the human PER1 (hPER1) gene is synergistically activated by protein kinases A and C (PKA, PKC) and cAMP responsive element binding protein. Activators and inhibitors of PKA as well as PKC modulate endogenous hPER1 expression and hPER1 promoter-driven reporter gene activity in a dose-dependent manner. Our results suggest that the hPER1 promoter acts as a sensor for multiple signaling molecules thereby integrating different physiological parameters. This regulation of hPER1 appears to be significant for rapid adaptation to changing environmental conditions.