The Cell Adhesion Molecule Necl-4/CADM4 Serves as a Novel Regulator for Contact Inhibition of Cell Movement and Proliferation

Contact inhibition of cell movement and proliferation is critical for proper organogenesis and tissue remodeling. We show here a novel regulatory mechanism for this contact inhibition using cultured vascular endothelial cells. When the cells were confluently cultured, Necl-4 was up-regulated and localized at cell–cell contact sites where it cis-interacted with the vascular endothelial growth factor (VEGF) receptor. This interaction inhibited the tyrosine-phosphorylation of the VEGF receptor through protein-tyrosine phosphatase, non-receptor type 13 (PTPN13), eventually reducing cell movement and proliferation. When the cells were sparsely cultured, Necl-4 was down-regulated but accumulated at leading edges where it inhibited the activation of Rho-associated protein kinase through PTPN13, eventually facilitating the VEGF-induced activation of Rac1 and enhancing cell movement. Necl-4 further facilitated the activation of extracellular signal-regulated kinase 1/2, eventually enhancing cell proliferation. Thus, Necl-4 serves as a novel regulator for contact inhibition of cell movement and proliferation cooperatively with the VEGF receptor and PTPN13.     

A putative GDP–GTP exchange factor is required for development of the excretory cell in Caenorhabditis elegans

The Caenorhabditis elegans excretory cell extends tubular processes, called canals, along the basolateral surface of the epidermis. Mutations in the exc-5 gene cause tubulocystic defects in this canal. Ultrastructural analysis suggests that exc-5 is required for the proper placement of cytoskeletal elements at the apical epithelial surface. exc-5 encodes a protein homologous to guanine nucleotide exchange factors and contains motif architecture similar to that of FGD1, which is responsible for faciogenital dysplasia. exc-5 interacts genetically with mig-2, which encodes Rho GTPase. These results suggest that EXC-5 controls the structural organization of the excretory canal by regulating Rho family GTPase activities.     

Sequential polymerization of flagellin A and flagellin B into Caulobacter flagella

The mode of polymerization of two species of flagellins, flagellin A and flagellin B, in polar flagella of Caulobacter crescentus was examined. By immunological staining we found that 1 to 1.2 μm of the portion of the flagellar filament proximal to the cell was composed of flagellin B, whereas about 5 μm of the distal portion was composed of flagellin A. This result, together with the previous observation that a flagellin B-less mutant cannot form normal flagella but instead forms stubs in spite of their high level of flagellin A synthesis, indicates that flagellin B is very important for the formation of complete flagella and/or for the initiation of filament formation from the hook.     

Tissue producing the serum factor stimulating the release of cathepsin D from lysosomes in vitro

Pancreatectomy as well as thyroparathyroidectomy resulted in the quick disappearance of a serum factor (stimulating cathepsin D release from lysosomes in vitro) from the rat or mouse blood. Extirpation of other organs such as duodenum, stomach, spleen, kidney, submaxillary gland, testis, adrenal gland or hypophysis, showed no effect on the serum factor level. Glucagon (but not insulin or thyroxine) given to the pancreatectomized animals restored the serum factor level in a dose-dependent manner. The serum factor-like activity was detected only in the parathyroids (but not thyroid), and the release of activity from parathyroid-slices was stimulated by glucagon, suggesting that the parathyroid may produce and/or secrete the serum factor under the influence of glucagon.     

RNA-Induced Interference with Animal Virus Infection

Some RNAs, including both single- and double-stranded RNAs, when incubated with chick embryo cell culture induce cellular resistance against viruses. Evidence was now obtained indicating that the induction of cellular resistance by RNA depends on the cellular metabolic activity, especially on the synthesis of cellular RNA and protein. Thus, inhibitors of RNA and protein synthesis, actinomycin D and cycloheximide, were found to inhibit the development of an antiviral state when added before, or during the relatively early period of, incubation of the cells with RNA. In the course of induction of cellular resistance, three stages may be distinguished, the priming stage, the developing stage, and the established resistant stage.     

Biotic and Abiotic Factors Controlling Respiration Rates of Above- and Belowground Woody Debris of Fagus crenata and Quercus crispula in Japan

As a large, long-term pool and source of carbon and nutrients, woody litter is an important component of forest ecosystems. The objective of this study was to estimate the effect of the factors that regulate the rate of decomposition of coarse and fine woody debris (CFWD) of dominant tree species in a cool-temperate forest in Japan. Respiration rates of dead stems, branches, and coarse and fine roots of Fagus crenata and Quercus crispula felled 4 years prior obtained in situ ranged from 20.9 to 500.1 mg CO₂ [kg dry wood]^–1 h^–1 in a one-time measurement in summer. Respiration rate had a significant negative relationship with diameter; in particular, that of a sample of Q. crispula with a diameter of >15 cm and substantial heartwood was low. It also had a significant positive relationship with moisture content. The explanatory variables diameter, [N], wood density, and moisture content were interrelated. The most parsimonious path model showed 14 significant correlations among 8 factors and respiration. Diameter and [C] had large negative direct effects on CFWD respiration rate, and moisture content and species had medium positive direct effects. [N] and temperature did not have direct or indirect effects, and position and wood density had indirect effects. The model revealed some interrelationships between controlling factors. We discussed the influence of the direct effects of explanatory variables and the influence especially of species and position. We speculate that the small R ² value of the most parsimonious model was probably due to the omission of microbial biomass and activity. These direct and indirect effects and interrelationships between explanatory variables could be used to develop a process-based CFWD decomposition model.