The Survival of Microorganisms in Space. Further Rocket and Balloon Borne Exposure Experiments

Rocket and balloon borne exposure experiments on survival of microorganisms in space environmen

Protein Kinase A Activity and Anchoring Are Required for Ovarian Cancer Cell Migration and Invasion

Epithelial ovarian cancer (EOC) is the deadliest of the gynecological malignancies, due in part to its clinically occult metastasis. Therefore, understanding the mechanisms governing EOC dissemination and invasion may provide new targets for antimetastatic therapies or new methods for detection of metastatic disease. The cAMP-dependent protein kinase (PKA) is often dysregulated in EOC. Furthermore, PKA activity and subcellular localization by A-kinase anchoring proteins (AKAPs) are important regulators of cytoskeletal dynamics and cell migration. Thus, we sought to study the role of PKA and AKAP function in both EOC cell migration and invasion. Using the plasma membrane-directed PKA biosensor, pmAKAR3, and an improved migration/invasion assay, we show that PKA is activated at the leading edge of migrating SKOV-3 EOC cells, and that inhibition of PKA activity blocks SKOV-3 cell migration. Furthermore, we show that while the PKA activity within the leading edge of these cells is mediated by anchoring of type-II regulatory PKA subunits (RII), inhibition of anchoring of either RI or RII PKA subunits blocks cell migration. Importantly, we also show – for the first time – that PKA activity is up-regulated at the leading edge of SKOV-3 cells during invasion of a three-dimensional extracellular matrix and, as seen for migration, inhibition of either PKA activity or AKAP-mediated PKA anchoring blocks matrix invasion. These data are the first to demonstrate that the invasion of extracellular matrix by cancer cells elicits activation of PKA within the invasive leading edge and that both PKA activity and anchoring are required for matrix invasion. These observations suggest a role for PKA and AKAP activity in EOC metastasis

A Direct Interaction with NEDD1 Regulates γ-Tubulin Recruitment to the Centrosome

The centrosome is the primary microtubule organizing centre of the cell. γ-tubulin is a core component of the centrosome and is required for microtubule nucleation and centrosome function. The recruitment of γ-tubulin to centrosomes is mediated by its interaction with NEDD1, a WD40-repeat containing protein. Here we demonstrate that NEDD1 is likely to be oligomeric in vivo and binds directly to γ-tubulin through a small region of just 62 residues at the carboxyl-terminus of the protein. This carboxyl-terminal domain that binds γ-tubulin has a helical structure and is a stable tetramer in solution. Mutation of residues in NEDD1 that disrupt binding to γ-tubulin result in a mis-localization of γ-tubulin away from the centrosome. Hence, this study defines the binding site on NEDD1 that is required for its interaction with γ-tubulin, and shows that this interaction is required for the correct localization of γ-tubulin

The Ordered Extension of Pseudopodia by Amoeboid Cells in the Absence of External Cues

Eukaryotic cells extend pseudopodia for movement. In the absence of external cues, cells move in random directions, but with a strong element of persistence that keeps them moving in the same direction Persistence allows cells to disperse over larger areas and is instrumental to enter new environments where spatial cues can lead the cell. Here we explore cell movement by analyzing the direction, size and timing of ∼2000 pseudopodia that are extended by Dictyostelium cells. The results show that pseudpopod are extended perpendicular to the surface curvature at the place where they emerge. The location of new pseudopods is not random but highly ordered. Two types of pseudopodia may be formed: frequent splitting of an existing pseudopod, or the occasional extension of a de novo pseudopod at regions devoid of recent pseudopod activity. Split-pseudopodia are extended at ∼60 degrees relative to the previous pseudopod, mostly as alternating Right/Left/Right steps leading to relatively straight zigzag runs. De novo pseudopodia are extended in nearly random directions thereby interrupting the zigzag runs. Persistence of cell movement is based on the ratio of split versus de novo pseudopodia. We identify PLA2 and cGMP signaling pathways that modulate this ratio of splitting and de novo pseudopodia, and thereby regulate the dispersal of cells. The observed ordered extension of pseudopodia in the absence of external cues provides a fundamental insight into the coordinated movement of cells, and might form the basis for movement that is directed by internal or external cues

Characterization of a nonvirulent variant of lymphocytic choriomeningitis virus

A cold-adapted, nonvirulent variant of the Armstrong strain of lymphocytic choriomeningitis virus was isolated from infected L929 cells maintained at 25° C. This variant, designated P17, was capable of replicating in the central nervous system of mice without causing disease and conferring immunity to back challenge with the parental strain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41689/1/705_2005_Article_BF01320786.pd

E2F1 Regulates Cellular Growth by mTORC1 Signaling

During cell proliferation, growth must occur to maintain homeostatic cell size. Here we show that E2F1 is capable of inducing growth by regulating mTORC1 activity. The activation of cell growth and mTORC1 by E2F1 is dependent on both E2F1's ability to bind DNA and to regulate gene transcription, demonstrating that a gene induction expression program is required in this process. Unlike E2F1, E2F3 is unable to activate mTORC1, suggesting that growth activity could be restricted to individual E2F members. The effect of E2F1 on the activation of mTORC1 does not depend on Akt. Furthermore, over-expression of TSC2 does not interfere with the effect of E2F1, indicating that the E2F1-induced signal pathway can compensate for the inhibitory effect of TSC2 on Rheb. Immunolocalization studies demonstrate that E2F1 induces the translocation of mTORC1 to the late endosome vesicles, in a mechanism dependent of leucine. E2F1 and leucine, or insulin, together affect the activation of S6K stronger than alone suggesting that they are complementary in activating the signal pathway. From these studies, E2F1 emerges as a key protein that integrates cell division and growth, both of which are essential for cell proliferation

Overexpression of Cathepsin Z Contributes to Tumor Metastasis by Inducing Epithelial-Mesenchymal Transition in Hepatocellular Carcinoma

The aim of this study was to characterize the oncogenic function and mechanism of Cathepsin Z (CTSZ) at 20q13.3, a frequently amplified region in hepatocellular carcinoma (HCC). Real-time PCR were used to compare CTSZ expression between paired HCC tumor and non-tumor specimens. CTSZ gene was stably transfected into HCC line QGY-7703 cells and its role in tumorigenicity and cell motility was characterized by soft agar, wound-healing, transwell invasion and cell adhesion assay, and tumor xenograft mouse model. Western blot analysis was used to study expression of proteins associated with epithelial-mesenchymal transition (EMT)

Tumour Suppressive Function and Modulation of Programmed Cell Death 4 (PDCD4) in Ovarian Cancer

Background: Programmed cell death 4 (PDCD4), originally identified as the neoplastic transformation inhibitor, was attenuated in various cancer types. Our previous study demonstrated a continuous down-regulation of PDCD4 expression in the sequence of normal-borderline-malignant ovarian tissue samples and a significant correlation of PDCD4 expression with disease-free survival. The objective of the current study was to further investigate the function and modulation of PDCD4 in ovarian cancer cells. Principal Findings: We demonstrated that ectopic PDCD4 expression significantly inhibited cell proliferation by inducing cell cycle arrest at G1 stage and up-regulation of cell cycle inhibitors of p27 and p21. Cell migration and invasion were also inhibited by PDCD4. PDCD4 over-expressing cells exhibited elevated phosphatase and tensin homolog (PTEN) and inhibited protein kinase B (p-Akt). In addition, the expression of PDCD4 was up-regulated and it was exported to the cytoplasm upon serum withdrawal treatment, but it was rapidly depleted via proteasomal degradation upon serum re-administration. Treatment of a phosphoinositide 3-kinase (PI3K) inhibitor prevented the degradation of PDCD4, indicating the involvement of PI3K-Akt pathway in the modulation of PDCD4. Conclusion: PDCD4 may play a critical function in arresting cell cycle progression at key checkpoint, thus inhibiting cell proliferation, as well as suppressing tumour metastasis. The PI3K-Akt pathway was implied to be involved in the regulatio

Methylation and Loss of Secreted Frizzled-Related Protein 3 Enhances Melanoma Cell Migration and Invasion

Wnt signaling is important in development and can also contribute to the initiation and progression of cancer. The Secreted Frizzled Related Proteins (SFRPs) constitute a family of Wnt modulators, crucial for controlling Wnt signaling. Here we investigate the expression and role of SFRP3 in melanoma

A Bacterial Cytotoxin Identifies the RhoA Exchange Factor Net1 as a Key Effector in the Response to DNA Damage

Background: Exposure of adherent cells to DNA damaging agents, such as the bacterial cytolethal distending toxin (CDT) or ionizing radiations (IR), activates the small GTPase RhoA, which promotes the formation of actin stress fibers and delays cell death. The signalling intermediates that regulate RhoA activation and promote cell survival are unknown. Principal Findings: We demonstrate that the nuclear RhoA-specific Guanine nucleotide Exchange Factor (GEF) Net1 becomes dephosphorylated at a critical inhibitory site in cells exposed to CDT or IR. Expression of a dominant negative Net1 or Net1 knock down by iRNA prevented RhoA activation, inhibited the formation of stress fibers, and enhanced cell death, indicating that Net1 activation is required for this RhoA-mediated responses to genotoxic stress. The Net1 and RhoAdependent signals involved activation of the Mitogen-Activated Protein Kinase p38 and its downstream target MAPKactivated protein kinase 2. Significance: Our data highlight the importance of Net1 in controlling RhoA and p38 MAPK mediated cell survival in cells exposed to DNA damaging agents and illustrate a molecular pathway whereby chronic exposure to a bacterial toxin ma