High expression of CXCR4 may predict poor survival in resected pancreatic adenocarcinoma

Chemokines and their receptors are involved in tumourigenicity and clinicopathological significance of chemokines receptor expression in pancreatic adenocarcinoma (PA) is not fully understood. This study was conducted to determine patients' outcome according to the expressions of CXCR4, CXCR7 and HIF-1α after resection of PA. Immunohistochemistry for CXCR4, CXCR7 and HIF-1α expressions as well as cell proliferative index (Ki-67) was conducted in 71 resected (R0) PA and their 48 related lymph nodes (LN) using tissue microarray. CXCR4 and CXCR7 expressions were positively correlated to HIF-1α suggesting a potential role of HIF-1α in CXCR4 and CXCR7 transcription activation. Patients with CXCR4high tumour expression had shorter OS than those with low expression (median survival: 9.7 vs 43.2 months, P=0.0006), a higher risk of LN metastases and liver recurrence. In multivariate analysis, high CXCR4 expression, LN metastases and poorly differentiated tumour are independent negative prognosis factors. In a combining analysis, patients with CXCR4low/CXCR7low tumour had a significantly shorter DFS and OS than patients with a CXCR7high/CXCR4high tumour. CXCR4 in resected PA may represent a valuable prognostic factor as well as an attractive target for therapeutic purpose

A late role for a subset of neurogenic genes to limit sensory precursor recruitments in Drosophila embryos

In Drosophila , mutations in a class of genes, the neurogenic genes, produce an excess of neurons. This neural hyperplasia has been attributed to the formation of more than the normal number of neuronal precursor cells at the expense of epidermal cells. In order to find out whether the neurogenic genes only act at this intial step of neurogenesis, we studied the replication pattern of the sensory organ precursor cells by monitoring BrdU incorporation in embryos mutant for Notch ( N ), Delta ( Dl ), mastermind ( mam ), almondex ( amx ), neuralized ( neu ), big brain ( bib ) and the Enhancer of split -Complex ( E ( spl )- C ). Using temperature sensitive alleles of two of the neurogenic genes, DI and N , we also induced an acute increase of replicating sensory precursors by shifting briefly to the restricted temperature. We have found that the loss of function of all the seven neurogenic loci that were tested causes an increase in replicating sensory precursor cells, consistent with the model that these neurogenic genes normally participate in the process of restricting the number of neuronal precursors. Whereas the temporal pattern of replication appeared normal in mutants of five of the seven neurogenic loci, in N and mam embryos replicating PNS cells are present beyond the time when they normally undergo replication. Experiments with colchicine suggest that many of these late replicating cells may be newly emerging precursors and probably not additional cell divisions of already recruited precursors. Thus, different neurogenic genes may be required over different periods of time for the specification of sensory precursor cells.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47511/1/427_2004_Article_BF00188736.pd

ppk23-Dependent Chemosensory Functions Contribute to Courtship Behavior in Drosophila melanogaster

Insects utilize diverse families of ion channels to respond to environmental cues and control mating, feeding, and the response to threats. Although degenerin/epithelial sodium channels (DEG/ENaC) represent one of the largest families of ion channels in Drosophila melanogaster, the physiological functions of these proteins are still poorly understood. We found that the DEG/ENaC channel ppk23 is expressed in a subpopulation of sexually dimorphic gustatory-like chemosensory bristles that are distinct from those expressing feeding-related gustatory receptors. Disrupting ppk23 or inhibiting activity of ppk23-expressing neurons did not alter gustatory responses. Instead, blocking ppk23-positive neurons or mutating the ppk23 gene delayed the initiation and reduced the intensity of male courtship. Furthermore, mutations in ppk23 altered the behavioral response of males to the female-specific aphrodisiac pheromone 7(Z), 11(Z)-Heptacosadiene. Together, these data indicate that ppk23 and the cells expressing it play an important role in the peripheral sensory system that determines sexual behavior in Drosophila

C-Terminal Region of EBNA-2 Determines the Superior Transforming Ability of Type 1 Epstein-Barr Virus by Enhanced Gene Regulation of LMP-1 and CXCR7

Type 1 Epstein-Barr virus (EBV) strains immortalize B lymphocytes in vitro much more efficiently than type 2 EBV, a difference previously mapped to the EBNA-2 locus. Here we demonstrate that the greater transforming activity of type 1 EBV correlates with a stronger and more rapid induction of the viral oncogene LMP-1 and the cell gene CXCR7 (which are both required for proliferation of EBV-LCLs) during infection of primary B cells with recombinant viruses. Surprisingly, although the major sequence differences between type 1 and type 2 EBNA-2 lie in N-terminal parts of the protein, the superior ability of type 1 EBNA-2 to induce proliferation of EBV-infected lymphoblasts is mostly determined by the C-terminus of EBNA-2. Substitution of the C-terminus of type 1 EBNA-2 into the type 2 protein is sufficient to confer a type 1 growth phenotype and type 1 expression levels of LMP-1 and CXCR7 in an EREB2.5 cell growth assay. Within this region, the RG, CR7 and TAD domains are the minimum type 1 sequences required. Sequencing the C-terminus of EBNA-2 from additional EBV isolates showed high sequence identity within type 1 isolates or within type 2 isolates, indicating that the functional differences mapped are typical of EBV type sequences. The results indicate that the C-terminus of EBNA-2 accounts for the greater ability of type 1 EBV to promote B cell proliferation, through mechanisms that include higher induction of genes (LMP-1 and CXCR7) required for proliferation and survival of EBV-LCLs

The two major plant plasma membrane H+-ATPases display different regulatory properties.

The major plant plasma membrane H(+)-ATPases fall into two gene categories, subfamilies I and II. However, in many plant tissues, expression of the two subfamilies overlaps, thus precluding individual characterization. Yeast expression of PMA2 and PMA4, representatives of the two plasma membrane H(+)-ATPase subfamilies in Nicotiana plumbaginifolia, has previously shown that (i) the isoforms have distinct enzymatic properties and that (ii) PMA2 is regulated by phosphorylation of its penultimate residue (Thr) and binds regulatory 14-3-3 proteins, resulting in the displacement of the autoinhibitory C-terminal domain. To obtain insights into regulatory differences between the two subfamilies, we have constructed various chimeric proteins in which the 110-residue C-terminal-encoding region of PMA2 was progressively substituted by the corresponding sequence from PMA4. The PMA2 autoinhibitory domain was localized to a region between residues 851 and 915 and could not be substituted by the corresponding region of PMA4. In contrast to PMA2, PMA4 was poorly phosphorylated at its penultimate residue (Thr) and bound 14-3-3 proteins weakly. The only sequence difference around the phosphorylation site is located two residues upstream of the phosphorylated Thr. It is Ser in PMA2 (as in most members of subfamily I) and His in PMA4 (as in most members of subfamily II). Substitution of His by Ser in PMA4 resulted in an enzyme showing increased phosphorylation status, 14-13-3 binding, and ATPase activity, as well as improved yeast growth. The reverse substitution of Ser by His in PMA2 resulted in the failure of this enzyme to complement the absence of yeast H(+)-ATPases. These results show that the two plant H(+)-ATPase subfamilies differ functionally in their regulatory properties

Single point mutations distributed in 10 soluble and membrane regions of the Nicotiana plumbaginifolia plasma membrane PMA2 H+-ATPase activate the enzyme and modify the structure of the C-terminal region.

The Nicotiana plumbaginifolia pma2 (plasma membrane H+-ATPase) gene is capable of functionally replacing the H+-ATPase genes of the yeast Saccharomyces cerevisiae, provided that the external pH is kept above 5.0. Single point mutations within the pma2 gene were previously identified that improved H+-ATPase activity and allowed yeast growth at pH 4.0. The aim of the present study was to identify most of the PMA2 positions, the mutation of which would lead to improved growth and to determine whether all these mutations result in similar enzymatic and structural modifications. We selected additional mutants in total 42 distinct point mutations localized in 30 codons. They were distributed in 10 soluble and membrane regions of the enzyme. Most mutant PMA2 H+-ATPases were characterized by a higher specific activity, lower inhibition by ADP, and lower stimulation by lysophosphatidylcholine than wild-type PMA2. The mutants thus seem to be constitutively activated. Partial tryptic digestion and immunodetection showed that the PMA2 mutants had a conformational change making the C-terminal region more accessible. These data therefore support the hypothesis that point mutations in various H+-ATPase parts displace the inhibitory C-terminal region, resulting in enzyme activation. The high density of mutations within the first half of the C-terminal region suggests that this part is involved in the interaction between the inhibitory C-terminal region and the rest of the enzyme

Mechanical control of organ size in the development of the Drosophila wing disc

Control of cessation of growth in developing organs has recently been proposed to be influenced by mechanical forces acting on the tissue due to its growth. In particular, it was proposed that stretching of the tissue leads to an increase in cell proliferation. Using the model system of the Drosophila wing imaginal disc, we directly stretch the tissue finding a significant increase in cell proliferation, thus confirming this hypothesis. In addition, we characterize the growth over the entire growth period of the wing disc finding a correlation between the apical cell area and cell proliferation rate