bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress Relief in Alcoholism
Authors: Kiberstis Paula A.
Published: March 2008

Despite the success of psychosocial interventions such as Alcoholics Anonymous, chronic alcohol abuse remains a significant public health problem. Noting that stress is a relapse trigger in alcoholism,

George
et al
. explored whether pharmacological inhibition of the neurokinin 1 receptor (NK1R), a mediator of the brain’s stress response, would alleviate symptoms associated with alcohol dependence. Mice genetically deficient in NK1R consumed less alcohol than controls. A drug that antagonizes NK1R was used in a small, controlled study of recently detoxified alcoholic inpatients and showed promising activity, such as reducing alcohol cravings. However, these latter results need to be confirmed in much larger, longer-term studies.

D. T. George, J. Gilman, J. Hersh, A. Thorsell, D. Herion, C. Geyer, X. Peng, W. Kielbasa, R. Rawlings, J. E. Brandt, D. R. Gehlert, J. T. Tauscher, S. P. Hunt, D. Hommer, M. Heilig, Neurokinin 1 receptor antagonism as a possible therapy for alcoholism.
Science
319
, 1536-1539 (2008).
[Abstract]
[Full Text]
Unfolding Possible Cancer Target
Authors: Ray L. Bryan
Published: March 2008

Work from Ozcan
et
al
. weaves the unfolded protein response (UPR) [which is initiated in the endoplasmic reticulum (ER) when the capacity of the ER to produce properly folded proteins is exceeded] into a regulatory network regulating insulin signaling and apoptosis. The paper focuses on signaling through the mTORC1 complex, which regulates protein synthesis by controlling the activity of ribosomal protein S6 kinases and eukaryotic initiation factor 4E. Deletion or loss of function of the tuberous sclerosis complex genes (TSC1 and TSC2) leads to sustained activation of mTORC1. In mouse embryo fibroblasts lacking TSC1 and TSC2 or in tumor cells from

Tsc2
+/–

mice, the UPR response was activated. This UPR-dependent activation of the mitogen-activated protein kinase JNK and serine/threonine phosphorylation of insulin receptor substrate 1 provided a mechanism by which insulin receptor signaling was inhibited. Treatments that alleviated ER stress (such as the addition of a chemical chaperone that promoted proper protein folding) alleviated the defects in insulin signaling in

Tsc1
–/–

or

Tsc2
–/–

cells. When ER stress gets really out of hand, cells undergo apoptosis, and the authors showed that TSC-deficient cells had increased vulnerability to apoptosis when treated with chemical agents that enhance ER stress. The authors and Reiling and Sabatini in associated commentary discuss the appealing logic of having the UPR feed back onto the mTORC1 pathway, which responds to nutrients and regulates growth and proliferation, thus coordinating pathways regulating metabolism and survival. They further point out the possibility that the UPR may provide a target to promote elimination of tumor cells, specifically those cells lacking TSC proteins, or more generally in tumor cells whose rapid growth and high rates of protein synthesis might make them more vulnerable than normal cells.

U. Ozcan, L. Ozcan, E. Yilmaz, K. Düvel, M. Sahin, B. D. Manning, G. S. Hotamisligil, Loss of the tuberous sclerosis complex tumor suppressors triggers the unfolded protein response to regulate insulin signaling and apoptosis.
Mol. Cell
29
, 541-551 (2008).
[PubMed]

J. H. Reiling, D. M. Sabatini, Increased mTORC1 signaling UPRegulates stress.
Mol. Cell
29
, 533-535 (2008).
[PubMed]
A STIM for Resting Cells
Authors: Ray L. Bryan
Published: March 2008

One of the "Breakthroughs of the Year" noted in last year’s compendium at STKE was the discovery of the role of STIM proteins, particularly STIM1, in coupling stimulus-induced depletion of intracellular calcium stores to influx of extracellular calcium through the plasma membrane calcium channel Orai1. Brandman
et al
. have now capped off 2007 with a paper describing a key role of STIM2 in regulation of basal concentrations of calcium in the cytoplasm and endoplasmic reticulum (ER) in unstimulated cells. The authors used an siRNA screen to find proteins that regulated basal calcium concentrations in cultured human HeLa cells. They sensitized the cells to depletion of calcium regulatory proteins by exposing them to low or high concentrations of extracellular calcium for 24 hours. The protein that stood out as a positive regulator of basal calcium concentrations was STIM2. Automated low-magnification imaging of fluorescently tagged STIM2 showed that, like STIM1, the protein translocated to the plasma membrane when intracellular stores of calcium were depleted. However, STIM2 was sensitive to smaller changes in the concentration of calcium in the ER and seemed to be tuned to provide a linear response to small changes in basal concentrations of calcium, whereas STIM1 has a switchlike response to large changes in the concentration of calcium after receptor stimulation. Thus, the authors propose that STIM2 may help maintain a constant basal concentration of calcium in the cytoplasm and ER, thus avoiding accidental activation of calcium signaling pathways. STIM2 may also provide a way for weak receptor stimuli to allow persistent changes in calcium concentrations, with STIM1 operating primarily to handle strong receptor stimuli.

O. Brandman, J. Liou, W. S. Park, T. Meyer, STIM2 is a feedback regulator that stabilizes basal cytosolic and endoplasmic reticulum Ca
2+
levels.
Cell
131
, 1327-1339 (2007).
[PubMed]
Akirins Clarify NF-κB Signaling
Authors: Gough Nancy R.
Published: March 2008

Once again, the fruit fly has proven an invaluable tool for revealing information about the immune responses involving the transcription factor nuclear factor κB (NF-κB), as Beutler and Moresco emphasize. Goto
et al
. performed a genome-wide RNA interference (RNAi) screen in cultured
Drosophila
S2 cells for genes required for NF-κB-dependent gene expression and found the gene
CG8580
, which they renamed
Akirin
(for the Japanese akiraka ni suru, meaning "making things clear"). The authors determined that
Drosophila
has a single
Akirin
gene, which is essential for viability, and there are two in mammals (
Akirin1
, which is not essential for viability in mice, and
Akirin2
, which is). Transfection experiments with tagged versions of the proteins indicated that Akirins are localized to the nucleus, and the nuclear localization signal is the only recognizable motif in these proteins. S2 cells in which Akirin was knocked down showed defective activation of gene expression in response to stimuli that activate the Imd pathway, which mediates immune response to Gram-negative bacteria through the activation of the NF-κB homolog Relish. In contrast, the response to signaling through the Toll pathway, which mediates the response to Gram-positive bacteria through the activation of the NF-κB homolog Dif was not affected. Epistasis experiments placed Akirin at the level of Relish in the Imd pathway. In flies, knockdown of Akirin led to decreased survival after Gram-negative bacterial infection. Analysis of Akirin1 or Akirin2 knockout mouse embryo fibroblasts (MEFs) suggested that Akirin2 was the homolog involved in NF-κB signaling downstream of Toll-like receptors (TLRs) or the tumor necrosis factor (TNF) receptor. Furthermore, the human Akirin2 protein rescued S2 cells from defective Imd signaling caused by knockdown of endogenous Akirin. MEFs deficient for Akirin2 showed impaired expression of a subset of NF-κB-regulated genes, yet stimulation of NF-κB DNA binding and degradation of the inhibitor protein IκBα was not impaired. These results suggest that in mice, as in the fly, Akirin2 acts at the same level as NF-κB, and it will be interesting to see whether these two proteins form a complex, as has been recently reported for ribosomal protein S3 and NF-κB (see related resource).

A. Goto, K. Matsushita, V. Gesellchen, L. El Chamy, D. Kuttenkeuler, O. Takeuchi, J. A. Hoffmann, S. Akira, M. Boutros, J.-M. Reichhart, Akirins are highly conserved nuclear proteins required for NF-κB-dependent gene expression in drosophila and mice.
Nat. Immunol.
9
, 97-104 (2008).
[PubMed]

B. Beutler, E. M. Y. Moresco, Akirins versus infection.
Nat. Immunol.
9
, 7-9 (2008).
[PubMed]
Transporting Behavior?
Authors: Adler Elizabeth M.
Published: March 2008

Courtship behavior in male
Drosophila
is influenced by various sensory cues. For instance, the pheromone 7-tricosene inhibits male flies from courting other males. Grosjean
et al
. found that male flies in which a mutation disrupted the production of mRNA and protein for the amino acid transporter genderblind (
gb
[
KG07905
] mutants) frequently courted other males. Analysis of several genotypes revealed an inverse relationship between male-male courtship and abundance of genderblind protein, and
gb
RNAi mimicked the
gb
mutant phenotype. Moreover, conditional expression of RNAi directed against
gb
indicated that its effects on courtship involved modulation of adult brain function rather than development. Whereas wild-type males preferred courting decapitated females to courting decapitated males,
gb
mutants failed to show this preference, effects that persisted in the absence of visual cues. Courtship of males deficient in various pheromones (including 7-tricosene) by
gb
mutants decreased to levels comparable to courtship of pheromone-deficient males by wild-type males, a decrease that was reversed by 7-tricosene. Genderblind immunoreactivity was present in glia, but not neurons, and, noting that their previous research had shown decreased ambient extracellular glutamate concentrations in the
gb
[
KG07905
] mutants (predicted to enhance glutamatergic synaptic strength), the authors determined that genderblind was present in brain regions containing glutamatergic neurons. Increasing glutamatergic synaptic strength by overloading synaptic vesicles with glutamate promoted male-male courtship, whereas a glutamate-receptor antagonist inhibited male-male courtship in
gb
mutants. Thus, the authors conclude that glial modulation of extracellular glutamate concentration and thereby glutamatergic transmission affects male
Drosophila
courtship behavior. Levine discusses the research and notes the importance of precision in language as applied to insect behavior.

Y. Grosjean, M. Grillet, H. Augustin, J.-F. Ferveur, D. E. Featherstone, A glial amino-acid transporter controls synapse strength and courtship in
Drosophila
.
Nat.
Neurosci.
11
, 54-61 (2008).
[PubMed]

J. D. Levine, Glia and romance.
Nat. Neurosci.
11
, 8-10 (2008).
[PubMed]
Changing Her Ways
Authors: Adler Elizabeth M.
Published: March 2008

Sex peptide (SP, a component of seminal fluid) elicits marked changes in the behavior of female
Drosophila melanogaster
: They lay eggs and are no longer receptive to male courtship. Yapici
et al
. used a genome-wide transgenic RNA interference (RNAi) screen to identify a gene (
SPR
, for sex peptide receptor) whose disruption led to a decrease in egg laying. Whereas virgin
SPR
RNAi females behaved like control females, mated females, in addition to laying few eggs, failed to reject courtship by a second male. Similarly,
SPR
RNAi females remained receptive to courtship after exposure to SP. When
SPR
(predicted to encode a G protein-coupled receptor) was expressed in Chinese hamster ovary (CHO) cells, it responded to nanomolar concentrations of SP and the related peptide DUP99B (which also elicits the postmating response) but not to other
Drosophila
peptides. Experiments involving coexpression of chimeric heterotrimeric GTP-binding protein α subunits suggested that SPR coupled to Gα
i
, Gα
o
, or both, to regulate adenosine 3',5'-monophosphate (cAMP) concentrations. SPR was present in the brain and ventral nerve cord, as well as in the female reproductive tract, and, in a subset of neurons, was coexpressed with
fruitless
, a gene previously implicated in determination of courtship behavior. SPR knockdown in
fruitless
neurons mimicked SPR deficiency, whereas selective expression of
SPR
in
fruitless
neurons rescued the remating phenotype and partially rescued egg laying. Putative SPR orthologs were identified in other insect genomes, and those from
Drosophila pseudoobscura
,
Aedes aegypti
, and
Bombyx mori
responded to SP and DUP99B in the CHO cell assay. The authors predict that the identification of SPR may lead to new strategies for controlling insect pests, and, in commentary discussing this research in the context of male reproductive strategies, Griffith notes the similarity between
Drosophila
and vertebrate seminal fluid.

N. Yapici, Y.-J. Kim, C. Ribeiro, B. J. Dickson, A receptor that mediates the post-mating switch in
Drosophila
reproductive behaviour.
Nature
451
, 33-37 (2008).
[PubMed]

L. C. Griffith, Love hangover.
Nature
451
, 24-25 (2008).
[PubMed]
2007: Signaling Breakthroughs of the Year
Authors: Adler Elizabeth M. , Foley John F. , Gough Nancy R. , Ray L. Bryan
Published: March 2008

This year's notable advances in cell signaling span research into the signals that regulate the state of chromatin in the cell nucleus to those signals that modulate the social behavior of organisms. This year’s findings include unexpected mechanisms and players in immune signaling pathways; new insights into the mechanisms underlying cell differentiation and development; lessons from model organisms regarding organismal behavior; revelations regarding the dynamics of cell signaling pathways; increasing recognition of the ubiquity and complexity of ubiquitin and related molecules in signaling processes; and a family of channels that have cornered the market on peripheral sensory perception.
Nuclear Ubiquitin Ligases, NF-κB Degradation, and the Control of Inflammation
Authors: Natoli Gioacchino , Chiocca Susanna
Published: March 2008

Transcriptional control of the vast majority of genes involved in the inflammatory response requires the nuclear factor κB (NF-κB) family of transcription factors. Stimulation and termination of NF-κB activity are subject to stringent spatiotemporal control. According to the classical model of NF-κB regulation, both activation and termination mechanisms are centered on inhibitor of NF-κB (IκB) proteins. Whereas activation of NF-κB requires degradation of the IκBs, the main mechanism responsible for termination of NF-κB activity is the resynthesis of a specific IκB, IκBα, which sequesters NF-κB dimers in the nucleus and translocates them to the cytoplasm in an inactive form. Studies now show that an additional mechanism that is required to prevent the uncontrolled activity of NF-κB proteins is their nuclear degradation. At least two E3 ubiquitin ligases, one of which seems to be essential for control of nuclear NF-κB p65 (also known as RelA) in myeloid cells, have been identified. Moreover, additional evidence indicates that individual NF-κB dimers with particular activating or repressive properties may be differentially controlled by nuclear degradation, thus paving the way for the exploitation of NF-κB degradation pathways for therapeutic purposes.
Protons Keep Worms Regular
Authors: Ray L. Bryan
Published: March 2008

The worm
C. elegans
has a particularly active gut that voids its intestinal contents every 50 seconds. Part of this process is mediated by a contraction of posterior muscle cells in response to cues from intestinal cells. Beg
et al.
screened for mutant animals that did not have proper contractions of the posterior body and identified three genes,
pbo-4
,
pbo-5
, and
pbo-6
, all of which appear to function in a mechanism through which protons act as transmitters (analogous to neurotransmitters, except that they are not released from neurons) that bind to channel proteins on posterior muscle cells to cause contraction. The
pbo-4
gene encodes a Na
+
/H
+
exchanger localized to intestinal cells that swaps one Na
+
ion into the cell in exchange for an extruded H
+
ion. The
pbo-5
and
pbo-6
genes encode subunits of an ion channel that belongs to a family of proteins that contain a disulfide-bonded loop and are thus known as "Cys-loop" ligand-gated ion channels. Heterologous expression of PBO-5 and PBO-6 in
Xenopus
oocytes showed that the proteins had channel function that was activated by protons. In the worm, the authors detected rhythmic increases in proton concentrations outside intestinal cells with a green fluorescent protein sensor. Furthermore, release of chemically "caged" protons in the coelomic space between the intestinal cells and muscle induced muscle contraction. Such proton release restored contraction in the
pbo-4
mutants (which lack the Na
+
/H
+
exchanger) but did not cause contraction in the mutants lacking components of the channel, which thus appears to act as the proton receptor. Members of another family of acid-sensing ion channels are present in the central nervous system of vertebrates, and deletion of the gene encoding one family member in the mouse causes defects in learning and memory. This leads the authors to speculate that protons may also function as bona fide neurotransmitters in the vertebrate central nervous system. Kim and Zhen provide commentary.

A. A. Beg, G. G. Ernstrom, P. Nix, M. W. Davis, E. M. Jorgensen, Protons act as a transmitter for muscle contraction in
C. elegans
.
Cell
132
, 149-160 (2008).
[PubMed]

J. S. M. Kim, M. Zhen, Protons as intercellular messengers.
Cell
132
, 21-22 (2008).
[PubMed]
Vision from Afar
Authors: Adler Elizabeth M.
Published: March 2008

A research group that previously showed that overexpression of ceramidase (CDase) in
Drosophila
photoreceptors suppressed retinal degeneration in response to certain mutations has now made the intriguing discovery that CDase regulation of photoreceptor function is cell nonautonomous. CDases, which convert ceramide to sphingosine, play a key role in metabolism of the sphingolipids, a lipid family that comprises not only structural components of cell membranes but also signaling molecules. Acharya
et al
. created flies in which almost the entire eye was homozygous for a null mutation of CDase, whereas other regions were CDase heterozygous. Ultrastructural analysis revealed that the photoreceptors of the mosaic flies were structurally normal; furthermore, immunocytochemical analysis of eye discs and Western blot analysis of retinal extracts revealed CDase protein. Overexpression of CDase in the fat body or in mushroom body neurons (tissues distinct from the retina) rescued photoreceptor degeneration in arrestin mutants and stimulated rhabdomeric membrane turnover in rhodopsin-null mutants. Viable functional CDase-null mutants experienced light-dependent photoreceptor degeneration; interactions between rhodopsin and arrestins in the CDase-null mutant flies were abnormal, and the photoreceptors of dark-raised mutant flies failed to respond to light. Retinal extracts of CDase-null mutants in which CDase was overexpressed in the fat body showed CDase activity, and eye discs in these flies exhibited CDase immunoreactivity. Experiments with cultured
Drosophila
Schneider cells revealed that extracellular CDase hydrolyzed ceramide at the cell surface and was internalized to localize to endosomes. Thus, the authors conclude that CDase acts in a cell-nonautonomous manner to regulate
Drosophila
photoreceptor function and survival. Dolph discusses this research as well as research by Wang
et al
. implicating a SOCS box protein, which the authors named STOPS (slow termination of phototransduction), in
Drosophila
phototransduction.

J. K. Acharya, U. Dasgupta, S. S. Rawat, C. Yuan, P. D. Sanxaridis, I. Yonamine, P. Karim, K. Nagashima, M. H. Brodsky, S. Tsunoda, U. Acharya, Cell-nonautonomous function of ceramidase in photoreceptor homeostasis.
Neuron
57
, 69-79 (2008).
[PubMed]

T. Wang, X. Wang, Q. Xie, C. Montell, The SOCS box protein STOPS is required for phototransduction through its effects on phospholipase C.
Neuron
57
, 56-68 (2008).
[PubMed]

P. Dolph, New insights into
Drosophila
vision.
Neuron
57
, 1-2 (2008).
[PubMed]
EPCs at the Switch
Authors: Kiberstis Paula A.
Published: March 2008

To ensure a steady supply of oxygen and nutrients, tumors send signals that stimulate the growth of new blood vessels. Bone marrow-derived cells called endothelial progenitor cells (EPCs) are known to be recruited to the tumor-associated growing vessels, but the presence of these cells at only very low levels in the tumor vasculature has made it difficult to assess their functional contribution. Studying mouse models of lung metastasis, Gao
et al
. (see the Perspective by Rafii and Lyden) show that EPCs are critical regulators of the "angiogenic switch" that helps drive the progression of dormant micrometastases to lethal metastases. Genetic manipulations that blocked EPC mobilization in tumor-bearing mice inhibited angiogenesis, impaired formation of lung metastases, and increased survival time.

D. Gao, D. J. Nolan, A. S. Mellick, K. Bambino, K. McDonnell, V. Mittal, Endothelial progenitor cells control the angiogenic switch in mouse lung metastasis.
Science
319
, 195-198 (2008).
[Abstract]
[Full Text]

S. Rafii, D. Lyden, A few to flip the angiogenic switch.
Science
319
, 163-164 (2008).
[Summary]
[Full Text]
Cancer Antigens Uncovered
Authors: Simpson Stephen J.
Published: March 2008

The potential of T cells to invade and attack tumors forms the basis for some very promising avenues of cancer immunotherapy. However, progress is often hampered by poor characterization of the antigens that killer T lymphocytes use to target tumor cells. Savage
et al.
(see the Perspective by Schreiber and Rowley) describe a broadly recognized antigen in a mouse model of prostate cancer. Unusually, the antigen was derived from a ubiquitous histone protein that is normally compartmentalized away from detection by the immune system. However, in the context of the tumor, the antigen was revealed to potentially reactive T cells, which suggests that the tumor environment somehow bends the rules of antigen processing and engagement by the immune system. Because features of this model are similar to those seen in human cancers, the system may also be useful in exploring tumor detection and therapeutic immune intervention.

P. A. Savage, K. Vosseller, C. Kang, K. Larimore, E. Riedel, K. Wojnoonski, A. A. Jungbluth, J. P. Allison, Recognition of a ubiquitous self antigen by prostate cancer-infiltrating CD8
+
T lymphocytes.
Science
319
, 215-220 (2008).
[Abstract]
[Full Text]

H. Schreiber, D. A. Rowley, Quo vadis, specificity?
Science
319
, 164-165 (2008).
[Summary]
[Full Text]
An Emerging Picture of Synapse Formation: A Balance of Two Opposing Pathways
Authors: Ono Fumihito
Published: March 2008

The neuromuscular junction (NMJ) is a well-studied chemical synapse and has served as a tractable model system to clarify how synapse formation occurs. Proteins on both the presynaptic and postsynaptic sides collaborate to induce the high-density accumulation of acetylcholine receptors (AChRs) at the NMJ. Two opposing pathways work in this process: A dispersing pathway works through acetylcholine and the AChR, and a clustering pathway works through agrin and the transmembrane tyrosine kinase MuSK. The molecular mechanisms underlying these two signaling cascades are beginning to be understood.
Heads or Tails
Authors: Purnell Beverly A.
Published: March 2008

Planarians--tubular flatworms--can regenerate all of their body parts and entire organ systems after amputation. However, the mechanism by which the animal "knows" how to generate a head after head removal or a tail after tail removal, a property called regeneration polarity, is unknown. Gurley
et al.
and Petersen and Reddien now find that a conserved factor within the Wnt signaling pathway is used to distinguish head from tail. Decreased Wnt signaling through β-catenin causes the regeneration of heads, whereas activation of Wnt signaling induces tails. β-catenin also maintains the anteroposterior body axis in uncut animals.

K. A. Gurley, J. C. Rink, A. Sánchez Alvarado, β-catenin defines head versus tail identity during planarian regeneration and homeostasis.
Science
319
, 323-327 (2008).
[Abstract]
[Full Text]

C. P. Petersen, P. W. Reddien,
Smed
-β
catenin
-1 is required for anteroposterior blastema polarity in planarian regeneration.
Science
319
, 327-330 (2008).
[Abstract]
[Full Text]
Tumor Suppressor Yin-Yang
Authors: Purnell Beverly A.
Published: March 2008

The Wnt signal transduction pathway is a critical player in the development of animals. However, inappropriate activation of this pathway triggers tumorigenesis; for example, disruption of the adenomatous polyposis coli (APC) tumor suppressor, a negative regulator of Wnt signaling, results in colorectal carcinoma development. Although APC is well known to function in inhibiting gene expression, Takacs
et al.
now report that fruit fly homologs of APC have an opposing job in the activation of Wnt signaling. Separable domains in APC not only restrained inappropriate signaling when the Wnt signal was absent but also promoted signaling upon Wnt stimulation.

C. M. Takacs, J. R. Baird, E. G. Hughes, S. S. Kent, H. Benchabane, R. Paik, Y. Ahmed, Dual positive and negative regulation of Wingless signaling by adenomatous polyposis coli.
Science
319
, 333-336 (2008).
[Abstract]
[Full Text]
GABA Stems Proliferation
Authors: Adler Elizabeth M.
Published: March 2008

Cell proliferation and differentiation, processes that are inversely correlated, are typically regulated during the G1 phase of the cell cycle. Self-renewing stem cells need to proliferate and remain multipotent; indeed, embryonic stem (ES) cells may lack the G1 pathways through which proliferation is regulated. Andäng
et al
. identified γ-aminobutyric acid type A receptor (GABA
A
R) subunits and GABA synthetic enzymes in mouse ES cells and peripheral neural crest stem (NCS) cells and combined electrophysiological analysis with use of a voltage-sensitive dye to confirm that the cells contained functional GABA
A
Rs. The GABA
A
R agonist muscimol inhibited proliferation of cultured stem cells, whereas the antagonist bicuculline promoted it, as did knockdown of the GABA
A
R β3 subunit (GABA
A
R β3) with RNA interference. Cell cycle distribution analysis indicated that receptor activation promoted the accumulation of ES cells in S phase. Moreover, muscimol stimulated the phosphorylation of histone H2AX (which is involved in the S/G2 DNA damage checkpoint response) by means of the checkpoint kinases ataxia telangiectasia mutated (ATM) and ataxia telangiectasia, Rad3-related (ATR), even though no overt DNA damage was evident. Furthermore, GABA-dependent inhibition of proliferation depended on H2AX. Muscimol decreased the incorporation of bromodeoxyuridine into blastocysts in vivo, and injection of siRNA directed against GABA
A
R β3 into zygotes led to the faster development of blastocyst-stage embryos. GABA also regulated proliferation of NCS cells. Thus the proliferation of ES and NCS cells appears to be regulated through autocrine- or paracrine-derived GABA through a pathway that uses components of the DNA damage checkpoint response.

M. Andäng, J. Hjerling-Leffler, A. Moliner, T. K. Lundgren, G. Castelo-Branco, E. Nanou, E. Pozas, V. Bryja, S. Halliez, H. Nishimaru, J. Wilbertz, E. Arenas, M. Koltzenburg, P. Charnay, A. El Manira, C. F. Ibañez, P. Ernfors, Histone H2AX-dependent GABA
A
receptor regulation of stem cell proliferation.
Nature
451
, 460-464 (2008).
[PubMed]
Activating Aurora
Authors: Riddihough Guy
Published: March 2008

Cell division in eukaryotes requires tight spatial and temporal control of its many components. Aurora B kinase, as part of the chromosomal passenger complex (CPC), plays a critical role in regulating chromosome segregation to daughter cells. How is the activity of Aurora B itself controlled? Rosasco-Nitcher
et al
. show that Aurora B is regulated at several levels by the protein teleophase disc 60-kD (TD-60), which, like Aurora B, is also found at inner centromeres during metaphase. Interaction with TD-60 brings the CPC to the centromere and, in combination with microtubules, activates Aurora B. Furthermore, Aurora B can only act on previously phosphorylated substrates, whose phosphorylation is also enhanced by TD-60. Thus, TD-60 may function to ensure that high levels of Aurora B activity occur only at centromeres.

S. E. Rosasco-Nitcher, W. Lan, S. Khorasanizadeh, P. T. Stukenberg, Centromeric Aurora-B activation requires TD-60, microtubules, and substrate priming phosphorylation.
Science
319
, 469-472 (2008).
[Abstract]
[Full Text]
Stop and Go Signals
Authors: Foley John F.
Published: March 2008

The mitogen-activated protein kinase (MAPK) c-Jun N-terminal kinase (JNK) has been implicated in a number of neuropathologies, but a clear role for JNK in physiological processes in the brain has not been well defined. The effects of JNK in neuropathologies often do not correlate with the phosphorylation and activation of the transcription factor c-Jun, a target of activated JNK, which suggested to Thomas
et al
. that other neuronal substrates of JNK might exist. The authors searched a database of protein sequences to identify potential JNK substrates based on a consensus phosphorylation sequence and identified the AMPA-type glutamate receptor (GluR) subunits GluR2L and GluR4 as JNK targets. In vitro kinase assays showed the JNK1-mediated phosphorylation of GST fusion proteins that contained either the C terminus of GluR2L or that of GluR4. JNK1 is constitutively active in the brain, and the authors found that both GluR2L and GluR4 were constitutively phosphorylated in unstimulated rat cortical neurons in culture. This phosphorylation was blocked by an inhibitor of JNK but not by inhibitors of other MAPKs. Coimmunoprecipitation experiments showed the presence of complexes that contained JNK1, the JNK activator MAPK kinase 7, and either GluR2L or GluR4. Stimulation of neurons with NMDA, which activates NMDA-type glutamate receptors, resulted in the rapid dephosphorylation of GluR2L and GluR4, without affecting JNK activity, whereas inhibition of glutamatergic signaling by treatment of cells with tetrodotoxin resulted in the rapid phosphorylation of the receptor subunits. NMDA treatment also caused the internalization of GluR2L. JNK-mediated rephosphorylation of a fluorescently tagged GluR2L was necessary for reinsertion of the receptor into the plasma membrane following NMDA removal. Thus, JNK plays a physiological role in regulating AMPA receptor trafficking as a consequence of neuronal activity.

G. M. Thomas, D.-T. Lin, M. Nuriya, R. L. Huganir, Rapid and bi-directional regulation of AMPA receptor phosphorylation and trafficking by JNK.
EMBO
J
.
27
, 361-372 (2008).
[PubMed]
Hearing About Glutamate Transporters
Authors: Adler Elizabeth M.
Published: March 2008

Although three vesicular glutamate transporters (VGLUTs) have been identified, only two are found in identified glutamatergic neurons. In contrast, VGLUT3 is expressed in several populations of neurons that release other classical neurotransmitters, including inhibitory GABAergic interneurons in the hippocampus and cortex, as well as outside the nervous system. Seal
et al
. found that mice lacking VGLUT3 were profoundly deaf: They failed to show a startle response to loud noises and did not exhibit auditory evoked potentials. Electrophysiological analysis revealed a defect in signaling from the inner hair cells of the cochlea to the auditory nerve, and morphological analysis showed abnormalities of inner hair cell synapses, as well as a moderate loss of cochlear ganglion neurons. Immunofluorescence analysis revealed that VGLUT3 was present in synaptic regions of the inner hair cells of wild-type mice. Furthermore, expression of VGLUT3--but not VGLUT1 or VGLUT2--in the inner hair cells of the rat was confirmed by reverse transcription polymerase chain reaction. Whereas various conductances in the IHCs of the mice lacking VGLUT3 resembled those in wild-type mice, electrophysiological analysis indicated that they failed to release synaptic glutamate. In addition to the defect in the auditory pathway, electroencephalography revealed spontaneous cortical seizures, with little effect on motor activity, in mice lacking VGLUT3. The authors conclude that VGLUT3 is essential for hearing and plays an important role in the regulation of cortical excitability. Ahnert-Hilger and Jahn discuss the work and speculate on the implications of releasing both an excitatory and an inhibitory transmitter from the same neuron.

R. P. Seal, O. Akil, E. Yi, C. M. Weber, L. Grant, J. Yoo, A. Clause, K. Kandler, J. L. Noebels, E. Glowatzki, L. R. Lustig, R. H. Edwards, Sensorineural deafness and seizures in mice lacking vesicular glutamate transporter 3.
Neuron
57
, 263-275 (2008).
[PubMed]

G. Ahnert-Hilger, R. Jahn, Into great silence without VGLUT3.
Neuron
57
, 173-174 (2008).
[PubMed]
How Yeast Responds to Change
Authors: Ray L. Bryan
Published: March 2008

The origin of the rapid adaptive response of yeast cells to changes in environmental osmolarity has been unclear. Mettetal
et al.
(see the Perspective by Lipan) now show that increases in extracellular osmolarity activate the high-osmolarity glycerol signaling pathway, which changes transcription of particular target genes. By measuring the cellular response to pulses of medium with increased ionic strength, the authors were able to develop a predictive model of the dynamics of this regulatory system. Rather than changes in gene expression, which have often been suggested to be at the core of the response to osmotic shock, the fast response is actually dominated by a nontranscriptional response that probably involves altered glycerol transport.

J. T. Mettetal, D. Muzzey, C. Gómez-Uribe, A. van Oudenaarden, The frequency dependence of osmo-adaptation in
Saccharomyces cerevisiae
.
Science
319
, 482-484 (2008).
[Abstract]
[Full Text]

O. Lipan, Enlightening rhythms.
Science
319
, 417-418 (2008).
[Summary]
[Full Text]
Fast and Slow
Authors: Purnell Beverly A.
Published: March 2008

During gene transcription, some activator proteins bind cyclically to their promoters, with periodicities of ~30 seconds (fast cycling) or ~30 minutes (slow cycling). Karpova
et al
. now show that these different cycles are distinct but that the same transcription activator can engage in both cycling activities on the same promoter at the same time. It seems that the fast cycle is involved in transcription initiation, whereas the slow cycle modulates the number of promoters accessible for initiation.

T. S. Karpova, M. J. Kim, C. Spriet, K. Nalley, T. J. Stasevich, Z. Kherrouche, L. Heliot, J. G. McNally, Concurrent fast and slow cycling of a transcriptional activator at an endogenous promoter.
Science
319
, 466-469 (2008).
[Abstract]
[Full Text]
Human ITPK1: A Reversible Inositol Phosphate Kinase/Phosphatase That Links Receptor-Dependent Phospholipase C to Ca
2+
-Activated Chloride Channels
Authors: Saiardi Adolfo , Cockcroft Shamshad
Published: March 2008

Inositol 3,4,5,6-tetrakisphosphate [Ins(3,4,5,6)P
4
] is an inhibitor of the conductance of the Ca
2+
-activated chloride channels in the plasma membrane. These ion channels are required for salt and fluid secretion from epithelial cells, for cell volume homeostasis, and for electrical excitability in neurons and smooth muscle. The enzyme ITPK1 (inositol 1,3,4-triphosphate 5/6 kinase) is the source of Ins(3,4,5,6)P
4
. It can phosphorylate both Ins(1,3,4)P
3
at the 5 or 6 positions and Ins(3,4,5,6)P
4
at the 1 position and can also dephosphorylate Ins(1,3,4,5,6)P
5
to Ins(3,4,5,6)P
4
. A study now shows that these various enzyme activities manifested by ITPK1 provide a molecular mechanism that allows the receptor-activated changes in phospholipase C activity and consequent increases in the concentration of Ins(1,3,4)P
3
to regulate the abundance of Ins(3,4,5,6)P
4
. ITPK1 sequesters a tightly bound nucleotide that can accept a phosphate from, or donate a phosphate directly to, an inositol polyphosphate without the nucleotide being released in the bulk medium. This phenomenon of "intersubstrate" transfer is found only in the human enzyme, which can use Ins(1,3,4)P
3
to promote increased cellular concentrations of Ins(3,4,5,6)P
4
.
A Bioinformatics Approach to Addiction
Authors: Gough Nancy R.
Published: March 2008

Li
et al
. performed an analysis on peer-reviewed literature, spanning 30 years, that linked genes to addiction in an attempt to uncover new molecular pathways that contribute to addiction. The authors acknowledged that pathways are subjective concepts; however, their analysis did identify pathways previously implicated in addiction and also suggested that gonadotropin-releasing hormone signaling and gap junction signaling may contribute as well. Their analysis of pathways associated with four different addictive classes of drugs led to the development of a hypothetical molecular network based on these pathways and additional protein interaction data. Systems analysis of the "addiction" network suggested that calcium/calmodulin-dependent protein kinase II (CaMKII) may be a central regulator with two "fast" positive-feedback loops (based on second messenger and downstream effector signaling) and two "slow" positive-feedback loops (based on gene transcription and translation) interlinking through CaMKII. Although the predictions were not confirmed experimentally, the analysis points toward experimentally testable hypotheses, and the associated database provides a tool for addiction researchers.

C.-Y. Li, X. Mao, L. Wei, Genes and (common) pathways underlying drug addiction.
PLoS Comput. Biol.
4
, e2 (2008).
[PubMed]
Endocannabinoid Interactions
Authors: Adler Elizabeth M.
Published: March 2008

Noting that stimulation of metabotropic glutamate (mGlu) receptors attenuates release of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) in various brain regions by means of retrograde endocannabinoid signaling through presynaptic CB1 receptors (see Di Marzo and Cristino), Maccarrone
et al
. investigated endocannabinoid signaling in the striatum. A combination of pharmacological and electrophysiological analysis of striatal slices revealed that activation of mGlu5 receptors with 3,5-dihydroxyphenylglycine (DHPG) led to the CB1-dependent inhibition of GABA release. There are two principal endocannabinoids, anandamide and 2-arachidonoylglycerol (2-AG), and DHPG increased 2-AG concentration, but not that of anandamide, by stimulating activity of the 2-AG synthetic enzyme diacylglycerol lipase (DAGL) and inhibiting activity of the 2-AG degrading enzyme monoacylglycerol lipase (MAGL). Although functional interactions between anandamide and 2-AG had not previously been shown, pharmacological inhibition of fatty acid amide hydrolase (FAAH, the enzyme that degrades anandamide) blocked the DHPG-mediated increase in 2-AG and prevented its effects on GABAergic transmission, as did FAAH knockout. The stable anandamide derivative methanandamide also blocked DHPG-mediated increase in 2-AG and decreased basal 2-AG. Anandamide activates transient receptor potential vanilloid 1 (TRPV1) channels, and the TRPV1 agonist capsaicin inhibited the effects of DHPG on 2-AG concentration and GABAergic transmission as well, whereas pharmacological inhibition of FAAH and capsaicin failed to block the effects of DHPG on 2-AG and GABAergic transmission in mice lacking TRPV1. Manipulations that increased anandamide concentration were associated with decreased DAGL activity, and capsaicin blocked a DHPG-dependent increase in striatal glutathione (which stimulates DAGL). Thus, anandamide can inhibit the production and effects of striatal 2-AG through activation of TRPV1, effects that seem to involve a glutathione-dependent pathway.

M. Maccarrone, S. Rossi, M. Bari, V. De Chiara, F. Fezza, A. Musella, V. Gasperi, C. Prosperetti, G. Bernardi, A. Finazzi-Agrò, B. F Cravatt, D. Centonze, Anandamide inhibits metabolism and physiological actions of 2-arachidonoylglycerol in the striatum.
Nat. Neurosci.
11
, 152-159 (2008).
[PubMed]

V. Di Marzo, L. Cristino, Why endocannabinoids are not all alike.
Nat.
Neurosci.
11
, 124-126 (2008).
[PubMed]
Monogamy in the TGF-β Receptor Relationship
Authors: Gough Nancy R.
Published: March 2008

The transforming growth factor-β (TGF-β) superfamily includes bone morphogenetic proteins (BMPs), nodals, and activins, as well as TGF-βs. Unlike the other type I and type II receptors, which bind promiscuously to several members of the BMP, activin, and nodal families, the TGF-β receptor I (TβRI) and TGF-β receptor II (TβRII) bind only the TGF-βs (see Massagué). In addition to this ligand selectivity, only the type II receptor subunit TβRII has high affinity for the TGF-β ligand, and the TGF-β:TβRII complex recruits TβRI, whereas the receptors that interact with the other family members exhibit binding of ligands to both the type I and type II receptors. Groppe
et al
. provide insight into the mechanism for this cooperative and selective interaction by crystallizing the extracellular domains of TβRI, TβRII, and TGF-β3. The crystal showed a dimer of the ligand bound in a symmetrical complex with two of each receptor subunit. In contrast to the other ligands in the superfamily, TGF-β3 induced an interaction between an N-terminal extension in TβRII with TβRI that docks the TβRI subunit to the complex. Experiments with TβRII with mutations in the N-terminal extension region showed that this region was not necessary for binding of TGF-β3 to TβRII but was necessary for mediating the recruitment of TβRI (based on in vitro binding assays) and activation of the receptor complex (based on cellular receptor activation assays). Thus, a cooperative induced fit allows a subset of TGF-β ligands to selectively activate a specific receptor complex.

J. Groppe, C. S. Hinck, P. Samavarchi-Tehrani, C. Zubieta, J. P. Schuermann, A. B. Taylor, P. M. Schwarz, J. L. Wrana, A. P. Hinck, Cooperative assembly of TGF-β superfamily signaling complexes is mediated by two disparate mechanisms and distinct modes of receptor binding.
Mol. Cell
29
, 157-168 (2008).
[PubMed]

J. Massagué, A very private TGF-β receptor embrace.
Mol. Cell
29
, 149-150 (2008).
[PubMed]
EphA2 Destabilizes Adherens Junctions
Authors: Foley John F.
Published: March 2008

Ephs are receptor tyrosine kinases that are activated by membrane-bound ephrin ligands on adjacent cells. The Eph-ephrin system plays an important role in coordinating cell movement and organization in development. Some Ephs are associated with certain cancers, and their abundance in cancer cells seems to correlate with tumor malignancy; however, there has been some controversy as to the strength of this relationship. Fang
et al
. investigated the involvement of Ephs in promoting tumor malignancy in their study of EphA2 signaling in a human breast epithelial cell line (MCF-10A). The authors used a retrovirus to increase the abundance of EphA2 in these cells and demonstrated in cell-cell adhesion assays that MCF-10A cells that expressed wild-type EphA2, but not a signaling-deficient mutant EphA2 (ΔC), exhibited decreased cell-cell adhesion in response to ephrinA. Cell-cell contacts are mediated by E-cadherin (in a Ca
2+
-dependent fashion) and its associated catenin proteins, which are localized at contact points known as adherens junction complexes. Western blotting and immunofluorescence studies showed that the increased abundance of EphA2 had no effect on the abundance or phosphorylation state of any of the known components of the adherens junction complexes. However, depletion of Ca
2+
from the culture medium resulted in accelerated loss of E-cadherin from adherens junctions of cells that contained wild-type EphA2 compared to that in cells that contained ΔC. Further studies showed EphA2-mediated adherens junction destabilization involved Src protein kinase–mediated inhibition of p190RhoGAP, an inhibitor of the small guanosine triphosphatase Rho. These results suggest that the EphA2-stimulated increase in Rho activity may lead to a redistribution of E-cadherin and a loss in cell-cell adhesion, which could be a contributing factor in cancer cell migration and malignancy.

W. B. Fang, R. C. Ireton, G. Zhuang, T. Takahashi, A. Reynolds, J. Chen, Overexpression of EPHA2 receptor destabilizes adherens junctions via a RhoA-dependent mechanism.
J
.
Cell
Sci
.
121
, 358-368 (2008).
[Abstract]
[Full Text]
Growth and Survival—The Complete Toolkit
Authors: Kiberstis Paula A.
Published: March 2008

As tumors progress to a more aggressive state, they acquire multiple genetic alterations, some that have little functional impact and others that are essential for the continued growth and survival of the tumor cells. Schlabach
et al.
and Silva
et al.
have developed a functional genomics strategy that will allow, at a genome-wide level, systematic identification of genes required for cell growth and survival. Cell lines derived from human mammary and colorectal cancers and normal mammary tissue showed a similar pattern of so-called "essential" genes, with many residing within functional pathways known to be critical for fundamental cellular processes such as cell cycle and translational control. Importantly, however, additional genes were identified as being essential for the growth of specific cell lines. This functional genomics strategy complements the cancer genome sequencing approaches that have shown recent success and could set the stage for high-throughput discovery of cancer drugs.

M. R. Schlabach, J. Luo, N. L. Solimini, G. Hu, Q. Xu, M. Z. Li, Z. Zhao, A. Smogorzewska, M. E. Sowa, X. L. Ang, T. F. Westbrook, A. C. Liang, K. Chang, J. A. Hackett, J. W. Harper, G. J. Hannon, S. J. Elledge, Cancer proliferation gene discovery through functional genomics.
Science
319
, 620-624 (2008).
[Abstract]
[Full Text]

J. M. Silva, K. Marran, J. S. Parker, J. Silva, M. Golding, M. R. Schlabach, S. J. Elledge, G. J. Hannon, K. Chang, Profiling essential genes in human mammary cells by multiplex RNAi screening.
Science
319
, 617-620 (2008).
[Abstract]
[Full Text]
Interfering with Inflammation
Authors: Simpson Stephen J.
Published: March 2008

The efficient and selective targeting of small interfering RNA (siRNA) molecules to cells could help to harness this technology for treating disease. Peer
et al.
(see the Perspective by Szoka) combine nanoscale liposomal packaging of siRNAs with antibody targeting to immune cells. The targeted siRNA cargo was able to find and efficiently inactivate its target, a key cell-cycle regulating molecule called cyclin D1. Furthermore, the systemic injection of the packaged siRNA particles reversed pathology in a mouse model of inflammatory bowel disease.

D. Peer, E. J. Park, Y. Morishita, C. V. Carman, M. Shimaoka, Systemic leukocyte-directed siRNA delivery revealing cyclin D1 as an anti-inflammatory target.
Science
319
, 627-630 (2008).
[Abstract]
[Full Text]

F. Szoka, The art of assembly.
Science
319
, 578-579 (2008).
[Summary]
[Full Text]