The protein kinase mammalian target of rapamycin (mTOR) plays an important role in the coordinate regulation of cellular responses to nutritional and growth factor conditions. mTOR achieves these roles through interacting with raptor and rictor to form two distinct protein complexes, mTORC1 and mTORC2. Previous studies have been focused on mTORC1 to elucidate the central roles of the complex in mediating nutritional and growth factor signals to the protein synthesis machinery. Cell growth relies on coordinated regulation of signaling pathways that integrate cellular physiological status in response to nutrient levels, growth factor signals, and environmental stress. Impairment of the coordinated regulation can lead to disastrous effects on cell physiology, resulting in cell death or uncontrolled growth. mTOR, 2 a member of the phosphatidylinositol kinase-related kinase family, has been known as a central player in the signaling pathway that regulates cell growth in response to a variety of cellular signals derived from nutrient levels, growth factors, and environmental stress (2-4). mTOR plays a central role in the signaling network that regulates a variety of cellular processes including ribosome biogenesis, protein synthesis, autophagy, and actin cytoskeleton organization; human diseases such as cancer, diabetes, obesity, and harmatoma syndrome are associated with defects in mTOR signaling (5-9).Recent years have seen discoveries of several mTOR effectors and binding proteins. mTOR exists in two multiprotein complexes, mTORC1 and mTORC2. mTORC1 consists of mTOR, raptor, G␤L, and PRAS40, and it functions to regulate protein synthesis and cell growth in response to nutrient levels and growth factor signals (10 -14). mTORC1 regulates phosphorylations of at least two regulators of protein synthesis, S6K1 and 4E-BP1, and mediates nutrient and insulin signals to the cell growth machinery (2, 15). mTORC1 is regulated by TSC-Rheb (tuberous sclerosis complex-Ras homolog-enriched in brain) signaling (16 -19). mTORC2 consists of mTOR, rictor, G␤L, and Sin1, and it does not likely bind rapamycin-FK506-binding protein 12 complex, which makes mTORC2 distinctive from mTORC1 (13,20,21). Saccharomyces cerevisiae TORC2 consists of TOR2, LST8, AVO1 (Sin1 ortholog), and AVO3 (rictor ortholog) and two other components, AVO2 and BIT61, whose homologues have not been identified in higher eukaryotes (13,22,23). Functions and regulatory mechanisms of mTORC2 remain largely unknown. Recent studies showed that mTORC2 regulates protein kinase C ␣ phosphorylation, actin cytoskeleton organization, and Akt phosphorylation at 21,24,25). Recognizing the complex relationship between mTOR, S6K1, and * This study was supported by the Tuberous Sclerosis Alliance, the Minnesota Medical Foundation, American Heart Association Grant 0655706Z, and National Institutes of Health Grant DK072004. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in acc...

The nucleotide sequences of the partial rpoB gene were determined from 38 Legionella species, including 15 serogroups of Legionella pneumophila. These sequences were then used to infer the phylogenetic relationships among the Legionella species in order to establish a molecular differentiation method appropriate for them. The sequences (300 bp) and the phylogenetic tree of rpoB were compared to those from analyses using 16S rRNA gene and mip sequences. The trees inferred from these three gene sequences revealed significant differences. This sequence incongruence between the rpoB tree and the other trees might have originated from the high frequency of synonymous base substitutions and/or from horizontal gene transfer among the Legionella species. The nucleotide variation of rpoB enabled more evident differentiation among the Legionella species than was achievable by the 16S rRNA gene and even by mip in some cases. Two subspecies of L. pneumophila (L. pneumophila subsp. pneumophila and subsp. fraseri) were clearly distinguished by rpoB but not by 16S rRNA gene and mip analysis. One hundred and five strains isolated from patient tissues and environments in Korea and Japan could be identified by comparison of rpoB sequence similarity and phylogenetic trees. These results suggest that the partial sequences of rpoB determined in this study might be applicable to the molecular differentiation of Legionella species.

Increased gelatinolytic activity was observed in respiratory syncytial virus (RSV)-infected HEp-2 cells by using zymography. The anti-matrix metalloproteinase-9 (MMP-9) antibody specifically reduced the gelatinolytic activity suggesting that the increased gelatinolytic activity was due to the MMP-9. It was also supported by the results from immunofluorescent staining, treatment of MMP inhibitors, and RSV infection of the cell clones that were transfected with plasmids to express more MMP-9 and tissue type inhibitor of metalloproteinase-1 (TIMP-1). The gelatinolytic activity of extracellular MMP-9 in RSV-infected HEp-2 cells increased 1.5 +/- 0.2 fold compared with the control (p < 0.01). Cell surface MMP-9 expression was also clearly detected by immunofluorescent staining. Treatment with 1,10-phenanthroline (0.05 mM), ethylenediamine-tetraacetate (EDTA) (1.5 mM), and penta-O-galloyl-beta-D-glucose (PGG) (3.3 microM) inhibited RSV multiplication as well as syncytia formation. Furthermore, the average syncytia size increased when the cells expressing more MMP-9 were infected by RSV. In contrast, syncytia formation was inhibited in the cells manipulated to express TIMP-1. Thus, this study concludes that although RSV infection induces MMP-9, which can enhance the syncytia formation leading to RSV multiplication and spread it can be inhibited by MMP inhibitors.