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Annexin A6-mediated tumor suppression requires inhibition of calcium influx and down-regulation of the calcium-activated RasGRF2

ABSTRACT: Membrane association of the tumor suppressor, annexin A6 (AnxA6), has been shown to regulate plasma membrane permeability to extracellular Ca2+, inhibit anchorage-independent tumor cell growth and paradoxically, promote tumor cell motility by mechanisms that remains poorly understood. Here, we identified RasGRF2, a Ca2+-activated Ras-specific guanine nucleotide exchange factor, as a major effector of AnxA6-elicited tumor-associated phenotypes in breast cancer cells. We demonstrate that reduced expression or loss of AnxA6 in breast cancer cells is associated with up-regulation of RasGRF2, increased Ras activity and consequently, early onset and rapid growth of xenograft tumors. Meanwhile, up-regulation of AnxA6 in AnxA6-low breast cancer cells is associated with a decrease in Ras activity and growth of xenograft tumors but on the contrary, an increase in Cdc42 activity and EGF-stimulated cell motility. Inhibition of Ca2+ influx into AnxA6-low breast cancer cells via Ni2+-sensitive or non-selective Ca2+ channels dose-dependently suppressed the expression of RasGRF2, induced the expression of AnxA6 and consequently, inhibited tumor cell proliferation. Finally, aberrant expression of RasGRF2 may be triggered by AnxA6-mediated or pharmacological inhibition of non-selective Ca2+ channels and occurs at least in part, by promoter methylation. These data for the first time identify RasGRF2 as a major effector of AnxA6-dependent breast tumor growth and motility and that regulated Ca2+ influx and/or RasGRF2 may be potential therapeutic targets for rapidly growing AnxA6-low breast carcinomas

ORGANISM(S): Homo sapiens

PROVIDER: GSE72083 | GEO | 2015/08/15

SECONDARY ACCESSION(S): PRJNA292905

REPOSITORIES: GEO

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Project description:Analysis of transcriptome in moss Physcomitrella patens CNGCb null mutant at 25 and 34 degrees C for 30 minutes. Results provide insight into role of CNGCb in acquired thermotolerance induced by non-lethal heat treatment. Typically at dawn of a hot summer day, land plants need precise molecular thermometers to sense harmless increments in the ambient temperature to timely develop a heat-shock response (HSR) and accumulate protective heat shock proteins (Hsps), in anticipation of upcoming harmful temperatures at mid-day. Here, we found that the CNGCb gene from Physcomitrella patens and its Arabidopsis ortholog CNGC2, encode for a component of cyclic nucleotide gated Ca2+ channels acting as the primary thermosensors of land plant cells. Disruption of CNGCb or CNGC2 produced a hyper-thermosensitive phenotype, giving rise to a HSR and acquired thermotolerance at significantly milder heat-priming treatments than in wild type plants. In an aequorin-expressing moss, CNGCb loss-of-function caused altered Ca2+ signaling and a sustained Ca2+ influx. Patch clamp recordings on moss protoplasts showed the presence of three distinct thermo-responsive Ca2+-channels in wild type cells. Deletion of CNGCb led to a total absence of one, and it increased the open probability of the remaining two thermo-responsive Ca2+ channels. Thus, both in Arabidopsis and moss, CNGC2 and CNGCb are expected to form with other related CNGCs, heteromeric Ca2+ channels in the plasma membrane that respond to mild increments in the ambient temperature by triggering an optimal HSR, leading to the onset of plant acquired thermotolerance. The WT moss tissues were heat-shocked for a half an hour at 34°C and 38°C and CNGCb at 25and 34°C followed by liquid nitrogen freezing. Total RNA was isolated using RNeasy Mini Kit (QIAGEN, Hilden, Germany) and two biological replicate samples for each treatment, were extracted. An Agilent-certified microarray service lab (MOgene, LC, St. Louis, MO, USA) was used to verify the integrity of the RNA and perform the microarray experiments. Two biological replicates were performed.

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Annexin A6-mediated tumor suppression requires inhibition of calcium influx and down-regulation of the calcium-activated RasGRF2

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