Identification of an interaction between the TPalpha and TPbeta isoforms of the human thromboxane A2 receptor with protein kinase C-related kinase (PRK) 1: implications for prostate cancer

In humans, thromboxane (TX) A(2) signals through the TPα and TPβ isoforms of the TXA(2) receptor or TP. Here, the RhoA effector protein kinase C-related kinase (PRK) 1 was identified as an interactant of both TPα and ΤPβ involving common and unique sequences within their respective C-terminal (C)-tail domains and the kinase domain of PRK1 (PRK1(640-942)). Although the interaction with PRK1 is constitutive, agonist activation of TPα/TPβ did not regulate the complex per se but enhanced PRK1 activation leading to phosphorylation of its general substrate histone H1 in vitro. Altered PRK1 and TP expression and signaling are increasingly implicated in certain neoplasms, particularly in androgen-associated prostate carcinomas. Agonist activation of TPα/TPβ led to phosphorylation of histone H3 at Thr(11) (H3 Thr(11)), a previously recognized specific marker of androgen-induced chromatin remodeling, in the prostate LNCaP and PC-3 cell lines but not in primary vascular smooth muscle or endothelial cells. Moreover, this effect was augmented by dihydrotestosterone in androgen-responsive LNCaP but not in nonresponsive PC-3 cells. Furthermore, PRK1 was confirmed to constitutively interact with TPα/TPβ in both LNCaP and PC-3 cells, and targeted disruption of PRK1 impaired TPα/TPβ-mediated H3 Thr(11) phosphorylation in, and cell migration of, both prostate cell types. Collectively, considering the role of TXA(2) as a potent mediator of RhoA signaling, the identification of PRK1 as a bona fide interactant of TPα/TPβ, and leading to H3 Thr(11) phosphorylation to regulate cell migration, has broad functional significance such as within the vasculature and in neoplasms in which both PRK1 and the TPs are increasingly implicated.     

Effects of electromagnetic field emitted by cellular phones on the EEG during an auditory memory task: a double blind replication study

The effects of electromagnetic fields (EMF) emitted by cellular phones on the event related desynchronization/synchronization (ERD/ERS) of the 4-6, 6-8, 8-10, and 10-12 Hz electroencephalogram (EEG) frequency bands were studied in 24 normal subjects performing an auditory memory task. This study was a systematic replication of our previous work. In the present double blind study, all subjects performed the memory task both with and without exposure to a digital 902 MHz field in a counterbalanced order. We were not able to replicate the findings from our earlier study. All eight of the significant changes in our earlier study were not significant in the present double blind replication. Also, the effect of EMF on the number of incorrect answers in the memory task was inconsistent. We previously reported no significant effect of EMF exposure on the number of incorrect answers in the memory task, but a significant increase in errors was observed in the present study. We conclude that EMF effects on the EEG and on the performance on memory tasks may be variable and not easily replicable for unknown reasons.     

Crystal Structure of BamB Bound to a Periplasmic Domain Fragment of BamA,the Central Component of the β-Barrel Assembly Machine

The β-barrel assembly machinery (BAM) mediates folding and insertion of β-barrel outer membrane proteins (OMPs) into the outer membrane of Gram-negative bacteria. BAM is a five-protein complex consisting of the β-barrel OMP BamA and lipoproteins BamB, -C, -D, and -E. High resolution structures of all the individual BAM subunits and a BamD-BamC complex have been determined. However, the overall complex architecture remains elusive. BamA is the central component of BAM and consists of a membrane-embedded β-barrel and a periplasmic domain with five polypeptide translocation-associated (POTRA) motifs thought to interact with the accessory lipoproteins. Here we report the crystal structure of a fusion between BamB and a POTRA3–5 fragment of BamA. Extended loops 13 and 17 protruding from one end of the BamB β-propeller contact the face of the POTRA3 β-sheet in BamA. The interface is stabilized by several hydrophobic contacts, a network of hydrogen bonds, and a cation-π interaction between BamA Tyr-255 and BamB Arg-195. Disruption of BamA-BamB binding by BamA Y255A and probing of the interface by disulfide bond cross-linking validate the physiological relevance of the observed interface. Furthermore, the structure is consistent with previously published mutagenesis studies. The periplasmic five-POTRA domain of BamA is flexible in solution due to hinge motions in the POTRA2–3 linker. Modeling BamB in complex with full-length BamA shows BamB binding at the POTRA2–3 hinge, suggesting a role in modulation of BamA flexibility and the conformational changes associated with OMP folding and insertion.     

Defining the risks of mesenchymal stromal cell therapy

We address the issue of the potential for malignant transformation of cultured mesenchymal stromal cells (MSC) commonly used in clinical cell-therapy protocols and describe the culture conditions under which tumorigenesis is likely to be an extremely uncommon event.     

RASSF1A Promoter Methylation Levels Positively Correlate with Estrogen Receptor Expression in Breast Cancer Patients

The aim of this study was to investigate the relationship between the promoter methylation in five cancer-associated genes and clinicopathologic features for identification of molecular markers of tumor metastatic potential and hormone therapy response efficiency in breast cancer. The methylation levels in paraffin-embedded tumor tissues, plasma, and blood cells from 151 sporadic breast cancer patients and blood samples of 50 controls were evaluated by quantitative multiplex methylation-specific polymerase chain reaction. DNA methylation of RAS-association domain family member 1 (RASSF1A), estrogen receptor 1 (ESR1), cadherin 1, type 1, E-cadherin (CDH1), TIMP metallopeptidase inhibitor 3 (TIMP3) and spleen tyrosine kinase (SYK) genes was detected in the tumors of 124, 19, 15, 15, and 6 patients with mean levels of 48.45%, 3.81%, 2.36%, 27.55%, and 10.81%, respectively. Plasma samples exhibited methylation in the same genes in 25, 10, 15, 17, and 3 patients with levels of 22.54%, 17.20%, 22.87%, 31.93%, and 27.42%, respectively. Cumulative methylation results confirmed different spectra in tumor and plasma samples. Simultaneous methylation in tumors and plasma were shown in less than 17% of patients. RASSF1A methylation levels in tumor samples statistically differ according to tumor size (P = .029), estrogen receptor (ER) and progesterone receptor (PR) status (P = .000 and P = .004), and immunohistochemical subtype (P = .000). Moreover, the positive correlation was found between RASSF1A methylation levels and percentage of cancer cells expressing ER and PR. The direct relationship between RASSF1A promoter methylation and expression of ER could aid the prognosis of hormonal therapy response.     

Characterization of reproductive activity in captive male Eurasian lynx (Lynx lynx)

This study characterizes the reproductive activity of male European lynx kept in Central Russia. Four captive adult males were subjected to an electroejaculation prior to (November), during (March) and after (June) the breeding season. Concentration, motility and morphological integrity of spermatozoa as well as testis diameter and testosterone levels in serum were evaluated. Additionally, fecal samples were collected for 2 years to determine the fecal testosterone secretion. Testis sizes and serum testosterone concentrations were characterized by little changes with highest levels in March (2.98 mm³; 1.96 ng/ml testosterone) and lowest in June (2.34 mm³; 0.75 ng/ml testosterone). In faeces, the highest testosterone concentrations were measured in February followed by a second increase in May. The volume of ejaculates and percentages of motile and intact spermatozoa reached the maxima in March. By performing two-male mating experiments, we could prove multiple paternity within three litters. Paternity analysis of litter also revealed that 26 of 31 cubs (84%) were sired from the same male, independently from being the first or second mating partner of the respective female. This particular male showed the most developed and activated reproductive tract and also had the best semen quality, which seems to be important for sperm competition.     

The Tumor Suppressor Functions of p27kip1 Include Control of the Mesenchymal/Amoeboid Transition

In many human cancers, p27 downregulation correlates with a worse prognosis, suggesting that p27 levels could represent an important determinant in cell transformation and cancer development. Using a mouse model system based on v-src-induced transformation, we show here that p27 absence is always linked to a more aggressive phenotype. When cultured in three-dimensional contexts, v-src-transformed p27-null fibroblasts undergo a morphological switch from an elongated to a rounded cell shape, accompanied by amoeboid-like morphology and motility. Importantly, the acquisition of the amoeboid motility is associated with a greater ability to move and colonize distant sites in vivo. The reintroduction of different p27 mutants in v-src-transformed p27-null cells demonstrates that the control of cell proliferation and motility represents two distinct functions of p27, both necessary for it to fully act as a tumor suppressor. Thus, we highlight here a new p27 function in driving cell plasticity that is associated with its C-terminal portion and does not depend on the control of cyclin-dependent kinase activity.Dissemination of tumor cells is strictly linked to their ability to attach to and move within the extracellular matrix (ECM) in a three-dimensional (3D) environment. The use of 3D experimental model systems revealed that a higher complexity in cell migration and adaptation responses exists in the 3D model than in the classical 2D model (10, 16, 41, 49). A striking example is given by the fact that only in 3D could individually migrating cells use different mechanisms such as mesenchymal and amoeboid motility (16, 17). The relative slow mesenchymal migration is characterized by a fibroblast-like spindle shape and is dependent on integrin-mediated adhesion and on protease function (16). The amoeboid motility can in some cases represent a less adhesive, integrin-independent type of movement. Cells use a propulsive mechanism and are highly deformable, and rather than degrade the matrix, they are able to squeeze through it (16). As a result, the cells that use the amoeboid motility can potentially move faster than cells that use a mesenchymal strategy. Mesenchymal and amoeboid movements are also characterized by a different involvement of small GTPases of the Rho family. A high RhoA activity is associated mainly with the amoeboid motility, while the mesenchymal migration needs a high Rac activity at the leading edge to promote the extension of cellular protrusions (41, 48). Under certain circumstances, cancer cells can undergo conversion from a mesenchymal toward an amoeboid motility, an event referred as mesenchymal-amoeboid transition (MAT) (50). MAT represents a putative escape mechanism in tumor cell dissemination that could be induced by inhibition of pericellular proteolysis (50) or by increased membrane-associated RhoA activity (18, 40).Key mediators of cell motility through ECM substrates are the members of the Src family kinases. The prototype of Src family kinases, c-Src (14), is activated following cell-ECM adhesion and contributes to regulate the focal adhesion turnover and the cytoskeletal modifications necessary for normal cell adhesion and motility (52). The c-Src gene is the proto-oncogene of the transforming gene v-src of Rous sarcoma virus, and its elevated protein level and activity have been found in many human tumors (20, 28, 27, 34). Despite the accumulation of information and new molecular understanding of how Src is controlled, there is still an incomplete picture about its role in the generation of the malignant phenotype. v-Src shows higher levels of the kinase activity and transforming ability than c-Src (14, 15, 52). It induces normal cells to acquire a variety of transformed features, including alteration of morphology and increase of invasion ability due to its role in focal adhesion remodeling (7, 9, 13).Many data suggest that there is a close relationship between cell-ECM interaction and the proliferation and movements in both normal and tumor cells (5, 38, 43). Accordingly, Src activation may influence not only cell motility but also cell cycle progression by targeting the cell cycle inhibitor p27^kip1 to proteasomal degradation (22, 39). Recent evidences indicated that p27^kip1 (hereafter called p27) can also regulate cell migration, even though its role still remains controversial since it has been reported to either block or stimulate cell movements (1, 4, 11, 19, 21, 23, 29, 45).Based on these notions, we tested the possible contribution of p27 to the growth and motility phenotypes induced by v-src transformation, with special regard to those cellular invasive features that can be observed in 3D environments. By studying in vitro and in vivo the behavior of wild-type (WT) and p27-null fibroblasts transformed with v-src, we highlight a new role for p27 in the regulation of cellular plasticity that can ultimately drive tumor cell shape, motility, and invasion.     

Photosynthesis is improved by exogenous calcium in heat-stressed tobacco plants

Effects of exogenous calcium chloride (CaCl₂) (20 mM) on photosynthetic gas exchange, photosystem II photochemistry, and the activities of antioxidant enzymes in tobacco plants under high temperature stress (43 °C for 2 h) were investigated. Heat stress resulted in a decrease in net photosynthetic rate (P_n), stomatal conductance as well as the apparent quantum yield (AQY) and carboxylation efficiency (CE) of photosynthesis. Heat stress also caused a decrease of the maximal photochemical efficiency of primary photochemistry (F_v/F_m). On the other hand, CaCl₂ application improved P_n, AQY, and CE as well as F_v/F_m under high temperature stress. Heat stress reduced the activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), whereas the activities of these enzymes either decreased less or increased in plants pretreated with CaCl₂; glutathione reductase (GR) activity increased under high temperature, and it increased more in plants pretreated with CaCl₂. There was an obvious accumulation of H₂O₂ and O₂⁻ under high temperature, but CaCl₂ application decreased the contents of H₂O₂ and O₂⁻ under heat stress conditions. Heat stress induced the level of heat shock protein 70 (HSP70), while CaCl₂ pretreatment enhanced it. These results suggested that photosynthesis was improved by CaCl₂ application in heat-stressed plants and such an improvement was associated with an improvement in stomatal conductance and the thermostability of oxygen-evolving complex (OEC), which might be due to less accumulation of reactive oxygen species.     

Physical Mapping of the Bacillus thuringiensis subsp. kurstaki and alesti Chromosomes

Two strains of the well-known insect pathogen and biopesticide, Bacillus thuringiensis (Bt), belonging to subspecies alesti (strain Bt5) and kurstaki (strain Bt213), were chosen for genetic characterization. The two strains belong to different serotypes and are currently classified into different subspecies, although their insecticidal activity is similar. Physical maps were constructed of Bt alesti and Bt kurstaki using Pulsed Field Gel Electrophoreses (PFGE), and the map positions of several genes were determined. The 5.5 Mb combined genetic and physical chromosome maps of the two strains were found to be indistinguishable, and the only differences detected between the strains were of extrachromosomal origin. A cryIA toxin gene probe hybridised to a chromosome fragment and to two extrachromosomal elements in both strains, migrating as 100 kb and 350 kb, respectively. In addition a cry hybridizing extrachromosomal element migrating as 80 kb was present only in Bt alesti. Both strains were also found to contain sequences hybridizing to an enterotoxin (hbla) gene probe. Such sequences were positioned on the 350 kb extrachromosomal element, as well as on the chromosome. Received: 20 April 2001 / Accepted: 29 May 2001