Involvement of gicerin, a cell adhesion molecule, in development and regeneration of oviduct and metastasis of oviductal adenocarcinomas of the chicken

Gicerin is a novel cell adhesion molecule in the immunoglobulin superfamily and has both homophilic adhesion and heterophilic adhesive activity to neurite outgrowth factor (NOF), an extracellular matrix protein in the laminin family. We investigated the possible involvement of gicerin in oviductal development, regeneration, and metastasis of oviductal adenocarcinomas of the chicken. In the oviductal epithelium, gicerin was expressed strongly during development, disappeared after maturation, and reappeared during regeneration. NOF was constitutively expressed in the basement membrane of the epithelium. These molecules were expressed strongly in oviductal adenocarcinomas in both primary and metastatic lesions in the mesentery. An anti-gicerin antibody inhibited the attachment of adenocarcinoma cells to the mesentery in vitro. Many cells migrated from adenocarcinoma tissues on NOF, which were inhibited by an anti-gicerin antibody. These results suggest that gicerin might play a role in oviductal development and regeneration and also in the metastasis of adenocarcinomas.     

Identification of substrate binding site of cyclin-dependent kinase 5

Cyclin-dependent kinase 5 (CDK5), unlike other CDKs, is active only in neuronal cells where its neuron-specific activator p35 is present. However, it phosphorylates serines/threonines in S/TPXK/R-type motifs like other CDKs. The tail portion of neurofilament-H contains more than 50 KSP repeats, and CDK5 has been shown to phosphorylate S/T specifically only in KS/TPXK motifs, indicating highly specific interactions in substrate recognition. CDKs have been shown to have a high preference for a basic residue (lysine or arginine) as the n+3 residue, n being the location in the primary sequence of a phosphoacceptor serine or threonine. Because of the lack of a crystal structure of a CDK-substrate complex, the structural basis for this specific interaction is unknown. We have used site-directed mutagenesis ("charged to alanine") and molecular modeling techniques to probe the recognition interactions for substrate peptide (PKTPKKAKKL) derived from histone H1 docked in the active site of CDK5. The experimental data and computer simulations suggest that Asp86 and Asp91 are key residues that interact with the lysines at positions n+2 and/or n+3 of the substrates.     

Tetracycline up-regulates COX-2 expression and prostaglandin E2 production independent of its effect on nitric oxide

Tetracyclines (doxycycline and minocycline) augmented (one- to twofold) the PGE2 production in human osteoarthritis-affected cartilage (in the presence or absence of cytokines and endotoxin) in ex vivo conditions. Similarly, bovine chondrocytes stimulated with LPS showed (one- to fivefold) an increase in PGE2 accumulation in the presence of doxycycline. This effect was observed at drug concentrations that did not affect nitric oxide (NO) production. In murine macrophages (RAW 264.7) stimulated with LPS, tetracyclines inhibited NO release and increased PGE2 production. Tetracycline(s) and L-N-monomethylarginine (L-NMMA) (NO synthase inhibitor) showed an additive effect on inhibition of NO and PGE2 accumulation, thereby uncoupling the effects of tetracyclines on NO and PGE2 production. The enhancement of PGE2 production in RAW 264.7 cells by tetracyclines was accompanied by the accumulation of both cyclooxygenase (COX)-2 mRNA and cytosolic COX-2 protein. In contrast to tetracyclines, L-NMMA at low concentrations (< or = 100 microM) inhibited the spontaneous release of No in osteoarthritis-affected explants and LPS-stimulated macrophages but had no significant effect on the PGE2 production. At higher concentrations, L-NMMA (500 microM) inhibited NO release but augmented PGE2 production. This study indicates a novel mechanism of action of tetracyclines to augment the expression of COX-2 and PGE2 production, an effect that is independent of endogenous concentration of NO.     

Milking of microalgae

The low productivity of algal cultures in the production of high-value compounds is the most significant bottleneck for commercialization of this technology. Cultures in which cell mass is reused for continuous production are proposed as a solution to overcome this problem. Recently, a method was developed in which beta-carotene was harvested from the microalga Dunaliella salina grown in a two-phase bioreactor. This raises the question of whether this technique could also be used in the mass production of secondary metabolites. Understanding the mechanism of the milking process and its relationship to the product formation pathway should reveal whether other products can be milked from various species of microalgae.     

Polycystin-1 activates and stabilizes the polycystin-2 channel

Autosomal dominant polycystic kidney disease (ADPKD) is a prevalent genetic disorder largely caused by mutations in the PKD1 and PKD2 genes that encode the transmembrane proteins polycystin-1 and -2, respectively. Both proteins appear to be involved in the regulation of cell growth and maturation, but the precise mechanisms are not yet well defined. Polycystin-2 has recently been shown to function as a Ca(2+)-permeable, non-selective cation channel. Polycystin-2 interacts through its cytoplasmic carboxyl-terminal region with a coiled-coil motif in the cytoplasmic tail of polycystin-1 (P1CC). The functional consequences of this interaction on its channel activity, however, are unknown. In this report, we show that P1CC enhanced the channel activity of polycystin-2. R742X, a disease-causing polycystin-2 mutant lacking the polycystin-1 interacting region, fails to respond to P1CC. Also, P1CC containing a disease-causing mutation in its coiled-coil motif loses its stimulatory effect on wild-type polycystin-2 channel activity. The modulation of polycystin-2 channel activity by polycystin-1 may be important for the various biological processes mediated by this molecular complex.