Veena Sangwan

The induction of kin genes in cold-acclimating Arabidopsis thaliana. Evidence of a role for calcium

Abstract. The involvement of calcium signaling during cold-induction of the kin genes of Arabidopsis thaliana (L.) Heynh. was examined. Treatments with chemicals which either chelate extracellular calcium (EGTA) or block the plasma-membrane calcium channels (La3+, Gd3+) inhibited cold acclimation as well as kin gene expression. Ruthenium red, an inhibitor of calcium release from intracellular stores partially inhibited kin gene expression and development of freezing tolerance. An inhibitor of calcium-dependent protein kinases (CDPKs) and calmodulin prevented cold acclimation as well as the cold induction of kin genes. Using restriction fragment length polymorphism-coupled domain-directed differential display, five CDPK clones were identified which showed differential regulation by cold. The amplified fragments showed homology to known plant CDPKs. The involvement of calcium andu2009calcium-binding proteins in cold acclimation of A.u2009thaliana is discussed.

In vivo and in vitro activation of temperature-responsive plant map kinases

Alfalfa cells possess two temperature‐responsive Mitogen‐Activated Protein Kinases (MAPKs), SAMK (Stress‐Activated MAP Kinase) activated at 4°C and HAMK (Heat shock‐Activated MAP Kinase) activated at 37°C. Both are inactive at 25°C. We show here that SAMK is activated when cells are transferred from 37°C to 25°C, and HAMK is activated when cells are transferred from 4°C to 25°C. Moreover, we show that heat activation of HAMK also occurs in cell‐free extracts. We conclude that (i) SAMK or HAMK activation does not require a particular temperature but a relative temperature shift, and (ii) that either HAMK itself or one or more of its upstream activators can sense temperature change directly.

Expression of DRD2 Is Increased in Human Pancreatic Ductal Adenocarcinoma and Inhibitors Slow Tumor Growth in Mice

BACKGROUND & AIMSnIncidence of and mortality from pancreatic ductal adenocarcinoma (PDAC), the most common form of pancreatic cancer, are almost equivalent, so better treatments are needed. We studied gene expression profiles of PDACs and the functions of genes with altered expression to identify new therapeutic targets.nnnMETHODSnWe performed microarray analysis to analyze gene expression profiles of 195 PDAC and 41 non-tumor pancreatic tissue samples. We undertook an extensive analysis of the PDAC transcriptome by superimposing interaction networks of proteins encoded by aberrantly expressed genes over signaling pathways associated with PDAC development to identify factors that might alter regulation of these pathways during tumor progression. We performed tissue microarray analysis to verify changes in expression of candidate protein using an independent set of 152 samples (40 nontumor pancreatic tissues, 63 PDAC sections, and 49 chronic pancreatitis samples). We validated the functional relevance of the candidate molecule using RNA interference or pharmacologic inhibitors in pancreatic cancer cell lines and analyses of xenograft tumors in mice.nnnRESULTSnIn an analysis of 38,276 human genes and loci, we identifiedxa01676 genes that were significantly up-regulated and 1166xa0genes that were significantly down-regulated in PDAC compared with nontumor pancreatic tissues. One gene that was up-regulated and associated with multiple signaling pathways that are dysregulated in PDAC was G protein subunit αi2, which has not been previously associated with PDAC. G protein subunit αi2 mediates the effects of dopamine receptor D2 (DRD2) on cyclic adenosine monophosphate signaling; PDAC tissues had a slight but significant increase in DRD2 messenger RNA. Levels of DRD2 protein were substantially increased in PDACs, compared with non-tumor tissues, in tissue microarray analyses. RNA interference knockdown of DRD2 or inhibition with pharmacologic antagonists (pimozide and haloperidol) reduced proliferation of pancreatic cancer cells, induced endoplasmic reticulum stress and apoptosis, and reduced cell migration. RNA interference knockdown of DRD2 in pancreatic tumor cells reduced growth of xenograft tumors in mice, and administration of the DRD2 inhibitor haloperidol to mice with orthotopic xenograft tumors reduced final tumor size and metastasis.nnnCONCLUSIONSnIn gene expression profile analysis of PDAC samples, we foundxa0the DRD2 signaling pathway to be activated. Inhibition of DRD2 in pancreatic cancer cells reduced proliferation and migration, and slowed growth of xenograft tumors in mice. DRD2 antagonists routinely used for management of schizophrenia might be tested in patients with pancreatic cancer.

5′-Inositol phosphatase SHIP2 recruits Mena to stabilize invadopodia for cancer cell invasion

Invadopodia are membrane protrusions used by cancer cells to remodel and invade the extracellular matrix. Here, Rajadurai et al. show that the lipid phosphatase SHIP2 recruits the Ena/VASP-family actin regulatory protein Mena to stabilize invadopodia membrane protrusions and promote cell invasion.

Early Events During Low Temperature Signaling

Environmental factors, such as temperature and water availability, are important determinants of plant growth, development and geographical distribution. Thus crop production is severely limited by stresses due to freezing temperatures and drought. The vulnerability of plants to environmental stresses is primarily due to their sessile growth habit. However, the same growth habit, by enforcing a selection pressure, has also led to the development of sophisticated mechanisms by which plants constantly monitor their environment and activate mechanisms to tolerate these stresses. Plants incapable of mounting such responses succumb to the stressful environment. Thus, freezing tolerant plants can survive sub-zero temperatures for months. They do so by sensing the non-lethal initial decline in temperature as seen in nature at the onset of winter and launching the processes involved in cold acclimation. Cold acclimation is a complex process comprising perception of non-freezing low temperature, transmission of this perception to the nucleus through a cascade of transduction events, and activation of gene transcription; products resulting from this step then confer freezing tolerance on the plant. Cold acclimation is a time-dependent process, the completion of which may take days or weeks. The state of acclimation temporally coincides with the stress and as the latter is relieved, de-acclimation occurs rapidly. Therefore, in order to improve crop production, and to extend geographical range of crop growth, a clear understanding of the processes involved in cold acclimation is essential.

Low Temperature Signal Transduction During Cold Acclimation of Alfalfa

Cold acclimation is the development of increased freezing tolerance in competent genotypes upon exposure to low but non-freezing temperatures over a period of days or weeks (Levitt, 1980). In nature, it is triggerred by declining temperature during the onset of winter and is quickly lost as temperature rises during spring. Cold acclimation can be reproduced in the laboratory by exposing the seedlings or cell suspension cultures to 2–5°C for a prolonged period and rapid deacclimation can be observed on returning the samples to 25°C.