PLCgamma2 Activates CREB-dependent Transcription in PC12 Cells Through Phosphorylation of CREB at Serine 133

Amino acid metabolic reprogramming in tumor metastatic colonization

Metastasis is considered as the major cause of cancer death. Cancer cells can be released from primary tumors into the circulation and then colonize in distant organs. How cancer cells acquire the ability to colonize in distant organs has always been the focus of tumor biology. To enable survival and growth in the new environment, metastases commonly reprogram their metabolic states and therefore display different metabolic properties and preferences compared with the primary lesions. For different microenvironments in various colonization sites, cancer cells must transfer to specific metabolic states to colonize in different distant organs, which provides the possibility of evaluating metastasis tendency by tumor metabolic states. Amino acids provide crucial precursors for many biosynthesis and play an essential role in cancer metastasis. Evidence has proved the hyperactivation of several amino acid biosynthetic pathways in metastatic cancer cells, including glutamine, serine, glycine, branched chain amino acids (BCAAs), proline, and asparagine metabolism. The reprogramming of amino acid metabolism can orchestrate energy supply, redox homeostasis, and other metabolism-associated pathways during cancer metastasis. Here, we review the role and function of amino acid metabolic reprogramming in cancer cells colonizing in common metastatic organs, including lung, liver, brain, peritoneum, and bone. In addition, we summarize the current biomarker identification and drug development of cancer metastasis under the amino acid metabolism reprogramming, and discuss the possibility and prospect of targeting organ-specific metastasis for cancer treatment.

Rh-CSF1 Attenuates Oxidative Stress and Neuronal Apoptosis via the CSF1R/PLCG2/PKA/UCP2 Signaling Pathway in a Rat Model of Neonatal HIE

Oxidative stress (OS) and neuronal apoptosis are major pathological processes after hypoxic-ischemic encephalopathy (HIE). Colony stimulating factor 1 (CSF1), binding to CSF1 receptor (CSF1R), has been shown to reduce neuronal loss after hypoxic-ischemia- (HI-) induced brain injury. In the present study, we hypothesized that CSF1 could alleviate OS-induced neuronal degeneration and apoptosis through the CSF1R/PLCG2/PKA/UCP2 signaling pathway in a rat model of HI. A total of 127 ten-day old Sprague Dawley rat pups were used. HI was induced by right common carotid artery ligation with subsequent exposure to hypoxia for 2.5 h. Exogenous recombinant human CSF1 (rh-CSF1) was administered intranasally at 1 h and 24 h after HI. The CSF1R inhibitor, BLZ945, or phospholipase C-gamma 2 (PLCG2) inhibitor, U73122, was injected intraperitoneally at 1 h before HI induction. Brain infarct volume measurement, cliff avoidance test, righting reflex test, double immunofluorescence staining, western blot assessment, 8-OHdG and MitoSOX staining, Fluoro-Jade C staining, and TUNEL staining were used. Our results indicated that the expressions of endogenous CSF1, CSF1R, p-CSF1R, p-PLCG2, p-PKA, and uncoupling protein2 (UCP2) were increased after HI. CSF1 and CSF1R were expressed in neurons and astrocytes. Rh-CSF1 treatment significantly attenuated neurological deficits, infarct volume, OS, neuronal apoptosis, and degeneration at 48 h after HI. Moreover, activation of CSF1R by rh-CSF1 significantly increased the brain tissue expressions of p-PLCG2, p-PKA, UCP2, and Bcl2/Bax ratio, but reduced the expression of cleaved caspase-3. The neuroprotective effects of rh-CSF1 were abolished by BLZ945 or U73122. These results suggested that rh-CSF1 treatment attenuated OS-induced neuronal degeneration and apoptosis after HI, at least in part, through the CSF1R/PLCG2/PKA/UCP2 signaling pathway. Rh-CSF1 may serve as therapeutic strategy against brain damage in patients with HIE.

Cause and effect of microenvironmental acidosis on bone metastases

Skeletal involvement is a frequent and troublesome complication in advanced cancers. In the process of tumor cells homing to the skeleton to form bone metastases (BM), different mechanisms allow tumor cells to interact with cells of the bone microenvironment and seed in the bone tissue. Among these, tumor acidosis has been directly associated with tumor invasion and aggressiveness in several types of cancer although it has been less explored in the context of BM. In bone, the association of local acidosis and cancer invasiveness is even more important for tumor expansion since the extracellular matrix is formed by both organic and hard inorganic matrices and bone cells are used to sense protons and adapt or react to a low pH to maintain tissue homeostasis. In the BM microenvironment, increased concentration of protons may derive not only from glycolytic tumor cells but also from tumor-induced osteoclasts, the bone-resorbing cells, and may influence the progression or symptoms of BM in many different ways, by directly enhancing cancer cell motility and aggressiveness, or by modulating the functions of bone cells versus a pro-tumorigenic phenotype, or by inducing bone pain. In this review, we will describe and discuss the cause of acidosis in BM, its role in BM microenvironment, and which are the final effectors that may be targeted to treat metastatic patients.

NSP-C contributes to the upregulation of CLOCK/BMAL1-mediated transcription

The bHLH-PAS transcription factors clock circadian regulator (CLOCK) and brain and muscle ARNT-like protein 1 (BMAL1) play essential roles in the generation of circadian gene expression rhythms through the activation of E-box-mediated transcription. Importantly, circadian transcriptional rhythms mediated by CLOCK/BMAL1 are observed in peripheral tissues as well as in the suprachiasmatic nucleus and contribute to tissue-specific functions. These findings suggest that CLOCK/BMAL1 have roles in many biological phenomena by interacting with various cellular regulators. In the present study, to understand the mechanisms underlying the multiple functional roles of CLOCK, we tried to identify new proteins that interact with CLOCK using a yeast two-hybrid system. We identified neuroendocrine-specific protein (NSP)-C, which is highly expressed in the brain, as a positive regulator of CLOCK/BMAL1-mediated transcription. We found that NSP-C interacted with CLOCK in mammalian cells. Co-expression of NSP-C with CLOCK/BMAL1 enhanced the transcriptional activation by CLOCK/BMAL1. Furthermore, knockdown of endogenous NSP-C by small interfering RNA (siRNA) suppressed E-box-mediated transcription, while this reduction of transcription was rescued by the expression of NSP-C protected from the action of siRNA. These observations suggest that NSP-C contributes to the upregulation of CLOCK/BMAL1-mediated transcription.

Unique Metabolic Adaptations Dictate Distal Organ-Specific Metastatic Colonization

Metastases arising from tumors have the proclivity to colonize specific organs, suggesting that they must rewire their biology to meet the demands of the organ colonized, thus altering their primary properties. Each metastatic site presents distinct metabolic challenges to a colonizing cancer cell, ranging from fuel and oxygen availability to oxidative stress. Here, we discuss the organ-specific metabolic adaptations that cancer cells must undergo, which provide the ability to overcome the unique barriers to colonization in foreign tissues and establish the metastatic tissue tropism phenotype.

Interactions between αCaMKII and calmodulin in living cells: conformational changes arising from CaM-dependent and -independent relationships

BACKGROUND

αCaMKII plays central and essential roles in long-term potentiation (LTP), learning and memory. αCaMKII is activated via binding with Ca²⁺/CaM in response to elevated Ca²⁺ concentration. Furthermore, prolonged increase in Ca²⁺ concentration leads to the auto-phosphorylation of αCaMKII at T286, maintaining the activation of αCaMKII even after Ca²⁺/CaM dissociation. Importantly, the active form of αCaMKII is thought to exhibit conformational change. In order to elucidate the relationships between the interaction of αCaMKII with CaM and the conformational change of αCaMKII, we generated molecular probes (YFP-αCaMKII with CFP-CaM and YFP-αCaMKII-CFP) and performed time-lapse imaging of the interaction with CaM and the conformational change, respectively, in living cells using FRET.

RESULTS

The interaction of YFP-αCaMKII with CFP-CaM and the conformational change of YFP-αCaMKII-CFP were induced simultaneously in response to increased concentrations of Ca²⁺. Consistent with previous predictions, high levels of Ca²⁺ signaling maintained the conformational change of YFP-αCaMKII-CFP at the time when CFP-CaM was released from YFP-αCaMKII. These observations indicated the transfer of αCaMKII conformational change from CaM-dependence to CaM-independence. Furthermore, analyses using αCaMKII mutants showed that phosphorylation at T286 and T305/306 played positive and negative roles, respectively, during in vivo interaction with CaM and further suggested that CaM-dependent and CaM-independent conformational changed forms displays similar but distinct structures.

CONCLUSIONS

Importantly, these structual differences between CaM-dependent and -independent forms of αCaMKII may exhibit differential functions for αCaMKII, such as interactions with other molecules required for LTP and memory. Our molecular probes could thus be used to identify therapeutic targets for cognitive disorders that are associated with the misregulation of αCaMKII.

Upregulation of CREB-mediated transcription enhances both short- and long-term memory

Unraveling the mechanisms by which the molecular manipulation of genes of interest enhances cognitive function is important to establish genetic therapies for cognitive disorders. Although CREB is thought to positively regulate formation of long-term memory (LTM), gain-of-function effects of CREB remain poorly understood, especially at the behavioral level. To address this, we generated four lines of transgenic mice expressing dominant active CREB mutants (CREB-Y134F or CREB-DIEDML) in the forebrain that exhibited moderate upregulation of CREB activity. These transgenic lines improved not only LTM but also long-lasting long-term potentiation in the CA1 area in the hippocampus. However, we also observed enhanced short-term memory (STM) in contextual fear-conditioning and social recognition tasks. Enhanced LTM and STM could be dissociated behaviorally in these four lines of transgenic mice, suggesting that the underlying mechanism for enhanced STM and LTM are distinct. LTM enhancement seems to be attributable to the improvement of memory consolidation by the upregulation of CREB transcriptional activity, whereas higher basal levels of BDNF, a CREB target gene, predicted enhanced shorter-term memory. The importance of BDNF in STM was verified by microinfusing BDNF or BDNF inhibitors into the hippocampus of wild-type or transgenic mice. Additionally, increasing BDNF further enhanced LTM in one of the lines of transgenic mice that displayed a normal BDNF level but enhanced LTM, suggesting that upregulation of BDNF and CREB activity cooperatively enhances LTM formation. Our findings suggest that CREB positively regulates memory consolidation and affects memory performance by regulating BDNF expression.

Selective genomic targeting by FRA-2/FOSL2 transcription factor: regulation of the Rgs4 gene is mediated by a variant activator protein 1 (AP-1) promoter sequence/CREB-binding protein (CBP) mechanism

FRA-2/FOSL2 is a basic region-leucine zipper motif transcription factor that is widely expressed in mammalian tissues. The functional repertoire of this factor is unclear, partly due to a lack of knowledge of genomic sequences that are targeted. Here, we identified novel, functional FRA-2 targets across the genome through expression profile analysis in a knockdown transgenic rat. In this model, a nocturnal rhythm of pineal gland FRA-2 is suppressed by a genetically encoded, dominant negative mutant protein. Bioinformatic analysis of validated sets of FRA-2-regulated and -nonregulated genes revealed that the FRA-2 regulon is limited by genomic target selection rules that, in general, transcend core cis-sequence identity. However, one variant AP-1-related (AP-1R) sequence was common to a subset of regulated genes. The functional activity and protein binding partners of a candidate AP-1R sequence were determined for a novel FRA-2-repressed gene, Rgs4. FRA-2 protein preferentially associated with a proximal Rgs4 AP-1R sequence as demonstrated by ex vivo ChIP and in vitro EMSA analysis; moreover, transcriptional repression was blocked by mutation of the AP-1R sequence, whereas mutation of an upstream consensus AP-1 family sequence did not affect Rgs4 expression. Nocturnal changes in protein complexes at the Rgs4 AP-1R sequence are associated with FRA-2-dependent dismissal of the co-activator, CBP; this provides a mechanistic basis for Rgs4 gene repression. These studies have also provided functional insight into selective genomic targeting by FRA-2, highlighting discordance between predicted and actual targets. Future studies should address FRA-2-Rgs4 interactions in other systems, including the brain, where FRA-2 function is poorly understood.

Characterization of the promoter of the mouse preproorexin gene

The neuropeptide Orexin is involved in the regulation of the sleep-awake cycle and feeding behavior. We isolated a 22-kb genomic clone containing the 5' flanking region of the mouse Orexin promoter. We determined that the transcription start site (+1) is located 96 nucleotides upstream of the initiation codon. The start site region contained consensus sequences corresponding to the transcription initiator and TATA box. Analysis of promoter activity using PC12 cells showed that regions between -13 and +112 and between -1,868 and -780 contained nerve growth factor (NGF)-responsive positive regulatory element and a negative regulatory element respectively.