Related Signaling Events Research Articles

Water channel aquaporin 4 is required for T cell receptor mediated lymphocyte activation.

Aquaporins are a family of ubiquitously expressed transmembrane water channels implicated in a broad range of physiological functions. We have previously reported that aquaporin 4 (AQP4) is expressed on T cells and that treatment with a small molecule AQP4 inhibitor significantly delays T cell mediated heart allograft rejection. Using either genetic deletion or small molecule inhibitor, we show that AQP4 supports T cell receptor mediated activation of both mouse and human T cells. Intact AQP4 is required for optimal T cell receptor (TCR)-related signaling events, including nuclear translocation of transcription factors and phosphorylation of proximal TCR signaling molecules. AQP4 deficiency or inhibition impairs actin cytoskeleton rearrangements following TCR crosslinking, causing inferior TCR polarization and a loss of TCR signaling. Our findings reveal a novel function of AQP4 in T lymphocytes and identify AQP4 as a potential therapeutic target for preventing TCR-mediated T cell activation.

Regulation of autophagy and lipid accumulation under phosphate limitation in Rhodotorula toruloides.

It is known that autophagy is essential for cell survival under stress conditions. Inorganic phosphate (Pi) is an essential nutrient for cell growth and Pi-limitation can trigger autophagy and lipid accumulation in oleaginous yeasts, yet protein (de)-phosphorylation and related signaling events in response to Pi limitation and the molecular basis linking Pi-limitation to autophagy and lipid accumulation remain elusive. Here, we compared the proteome and phosphoproteome of Rhodotorula toruloides CGMCC 2.1389 under Pi-limitation and Pi-repletion. In total, proteome analysis identified 3,556 proteins and the phosphoproteome analysis identified 1,649 phosphoproteins contained 5,659 phosphosites including 4,499 pSer, 978 pThr, and 182 pTyr. We found Pi-starvation-induced autophagy was regulated by autophagy-related proteins, but not the PHO pathway. When ATG9 was knocked down, the engineered strains produced significantly less lipids under Pi-limitation, suggesting that autophagy required Atg9 in R. toruloides and that was conducive to lipid accumulation. Our results provide new insights into autophagy regulation under Pi-limitation and lipid accumulation in oleaginous yeast, which should be valuable to guide further mechanistic study of oleaginicity and genetic engineering for advanced lipid producing cell factory.

Aptamer-Based Analysis and Manipulation of the Protein Activity in Living Cells.

Directly analyzing and precisely manipulating the activity of target proteins without altering their natural structure and expression would be essential to decoding many protein-dominant cellular processes. To meet this goal, we used streptavidin as the carrier to develop an aptamer-based nanoplatform for monitoring the activation process of specific proteins in living cells. Our results showed that this nanoplatform could efficiently enter the cellular cytoplasm and specifically report the presence of RelA in the activated state. Meanwhile, with incorporation of a photoresponsive module, this aptamer-based nanoplatform was able to manipulate the nuclear translocation behavior of active RelA, enabling control over related downstream signaling events.

JNK signaling-dependent regulation of histone acetylation are involved in anacardic acid alleviates cardiomyocyte hypertrophy induced by phenylephrine.

Cardiac hypertrophy is a complex process induced by the activation of multiple signaling pathways. We previously reported that anacardic acid (AA), a histone acetyltransferase (HAT) inhibitor, attenuates phenylephrine (PE)-induced cardiac hypertrophy by downregulating histone H3 acetylation at lysine 9 (H3K9ac). Unfortunately, the related upstream signaling events remained unknown. The mitogen-activated protein kinase (MAPK) pathway is an important regulator of cardiac hypertrophy. In this study, we explored the role of JNK/MAPK signaling pathway in cardiac hypertrophy induced by PE. The mice cardiomyocyte hypertrophy model was successfully established by treating cells with PE in vitro. This study showed that p-JNK directly interacts with HATs (P300 and P300/CBP-associated factor, PCAF) and alters H3K9ac. In addition, both the JNK inhibitor SP600125 and the HAT inhibitor AA attenuated p-JNK overexpression and H3K9ac hyperacetylation by inhibiting P300 and PCAF during PE-induced cardiomyocyte hypertrophy. Moreover, we demonstrated that both SP600125 and AA attenuate the overexpression of cardiac hypertrophy-related genes (MEF2A, ANP, BNP, and β-MHC), preventing cardiomyocyte hypertrophy and dysfunction. These results revealed a novel mechanism through which AA might protect mice from PE-induced cardiomyocyte hypertrophy. In particular, AA inhibits the effects of JNK signaling on HATs-mediated histone acetylation, and could therefore be used to prevent and treat pathological cardiac hypertrophy.

Effect of dietary NiCl2 on the cell cycle of cecal tonsil in the chicken broiler.

Although the effects of nickel chloride (NiCl2) on the immune system have long been recognized, little is known about the effects of nickel (II) on the cell cycle and related signaling events in immune organs, such as cecal tonsil, a key immune organ of chicken. In the present study, we investigated the effect of NiCl2 on the cell cycle of cecal tonsil. The cell cycle was detected by the methods of flow cytometry (FCM), quantitative real-time PCR (qRT-PCR) and immunohistochemistry (IHC). The results showed that dietary NiCl2 in excess of 300 mg/kg caused the G2/M cell cycle arrest and the reduction of cell proportion at S phase of the cecal tonsil. The G2/M cell cycle arrest was accompanied by the up-regulation of p53, p21 protein expression and mRNA expression, and down-regulation of cyclinB and proliferating cell nuclear antigen (PCNA) protein expression and mRNA expression. The data suggested that the cells' (mainly the T lymphocytes) proliferation in the cecal tonsil was inhibited by the high dietary NiCl2.

Single Cell Durotaxis Assay for Assessing Mechanical Control of Cellular Movement and Related Signaling Events

Single Cell Durotaxis Assay for Assessing Mechanical Control of Cellular Movement and Related Signaling Events

Single Cell Durotaxis Assay for Assessing Mechanical Control of Cellular Movement and Related Signaling Events.

Durotaxis is the process by which cells sense and respond to gradients of tension. In order to study this process in vitro, the stiffness of the substrate underlying a cell must be manipulated. While hydrogels with graded stiffness and long-term migration assays have proven useful in durotaxis studies, immediate, acute responses to local changes in substrate tension allow focused study of individual cell movements and subcellular signaling events. To repeatably test the ability of cells to sense and respond to the underlying substrate stiffness, a modified method for application of acute gradients of increased tension to individual cells cultured on deformable hydrogels is used which allows for real time manipulation of the strength and direction of stiffness gradients imparted upon cells in question. Additionally, by fine tuning the details and parameters of the assay, such as the shape and dimensions of the micropipette or the relative position, placement, and direction of the applied gradient, the assay can be optimized for the study of any mechanically sensitive cell type and system. These parameters can be altered to reliably change the applied stimulus and expand the functionality and versatility of the assay. This method allows examination of both long term durotactic movement as well as more immediate changes in cellular signaling and morphological dynamics in response to changing stiffness.

Selenium maintains Ca2+ homeostasis in sheep lymphocytes challenged by oxidative stress.

Selenium (Se) is an essential element in human and animal diets, based upon a widespread range of beneficial effects that are primarily due to its antioxidant properties. While Se can be associated to anti-cancer and anti-diabetic activities, reproductive efficiency, and enhancement of the immune system, the mechanistic details of the corresponding biological processes are still largely elusive. To avoid deficiencies and increase bioavailability, Se it is generally supplied to livestock through Se-supplemented feeds or forage plants fertilized with inorganic Se. While the relationship between Ca2+ and ROS (reactive oxygen species) is well known, only a few studies have addressed the possible involvement of Se in the control of cytosolic Ca2+ in oxidative stress. The results on Ca2+ homeostasis were obtained adding exogenous Se in the form of SeO42- to sheep lymphomonocytes cultured in vitro. In particular, Se strongly attenuated 1mM H2O2-induced alteration of intracellular [Ca2+]C as well as the entry of extracellular Ca2+ into the cells with comparable EC50 values for sodium selenate accounting to 1.72 and 2.28 mM, respectively. In an ex vivo trial, it was observed that Ca2+ homeostasis can effectively be rescued in sheep lymphomonocytes exposed in vivo to a Se concentration of approximately 1.9 mM, that was achieved by feeding sheep with olive leaves previously sprayed with 500 mg/plant Na-selenate. Thus the results obtained suggest that the mode of action of selenium markedly influenced Ca2+-related signaling events. Furthermore, results clearly reveal that the protective effect of Se on Ca2+ homeostasis under oxidative challenge can be clearly and effectively achieved through an appropriate dietary regimen obtained also in a circular economy logic using pruning of olive trees treated to reduce tree drought stress.

Promoting Glucose Transporter-4 Vesicle Trafficking along Cytoskeletal Tracks: PAK-Ing Them Out.

Glucose is the principal cellular energy source in humans and maintenance of glucose homeostasis is critical for survival. Glucose uptake into peripheral skeletal muscle and adipose tissues requires the trafficking of vesicles containing glucose transporter-4 (GLUT4) from the intracellular storage compartments to the cell surface. Trafficking of GLUT4 storage vesicles is initiated via the canonical insulin signaling cascade in skeletal muscle and fat cells, as well as via exercise-induced contraction in muscle cells. Recent studies have elucidated steps in the signaling cascades that involve remodeling of the cytoskeleton, a process that underpins the mechanical movement of GLUT4 vesicles. This review is focused upon an alternate phosphoinositide-3 kinase-dependent pathway involving Ras-related C3 botulinum toxin substrate 1 signaling through the p21-activated kinase p21-activated kinase 1 and showcases related signaling events that co-regulate both the depolymerization and re-polymerization of filamentous actin. These new insights provide an enriched understanding into the process of glucose transport and yield potential new targets for interventions aimed to improve insulin sensitivity and remediate insulin resistance, pre-diabetes, and the progression to type 2 diabetes.

Alterations in fatty acid metabolism and sirtuin signaling characterize early type-2 diabetic hearts of fructose-fed rats.

Despite the fact that skeletal muscle insulin resistance is the hallmark of type‐2 diabetes mellitus (T2DM), inflexibility in substrate energy metabolism has been observed in other tissues such as liver, adipose tissue, and heart. In the heart, structural and functional changes ultimately lead to diabetic cardiomyopathy. However, little is known about the early biochemical changes that cause cardiac metabolic dysregulation and dysfunction. We used a dietary model of fructose‐induced T2DM (10% fructose in drinking water for 6 weeks) to study cardiac fatty acid metabolism in early T2DM and related signaling events in order to better understand mechanisms of disease. In early type‐2 diabetic hearts, flux through the fatty acid oxidation pathway was increased as a result of increased cellular uptake (CD36), mitochondrial uptake (CPT1B), as well as increased β‐hydroxyacyl‐CoA dehydrogenase and medium‐chain acyl‐CoA dehydrogenase activities, despite reduced mitochondrial mass. Long‐chain acyl‐CoA dehydrogenase activity was slightly decreased, resulting in the accumulation of long‐chain acylcarnitine species. Cardiac function and overall mitochondrial respiration were unaffected. However, evidence of oxidative stress and subtle changes in cardiolipin content and composition were found in early type‐2 diabetic mitochondria. Finally, we observed decreased activity of SIRT1, a pivotal regulator of fatty acid metabolism, despite increased protein levels. This indicates that the heart is no longer capable of further increasing its capacity for fatty acid oxidation. Along with increased oxidative stress, this may represent one of the earliest signs of dysfunction that will ultimately lead to inflammation and remodeling in the diabetic heart.

Abstract 1398: Metastatic neuroblastoma cancer stem cells exhibit flexible plasticity and adaptive stemness signaling

Abstract High-risk neuroblastoma (HR-NB) presented with hematogenous metastasis is one of the most difficult cancers to cure with poor patient survival. Aggressive tumors contain populations of rapidly proliferating clonogens that exhibit stem cell properties, cancer stem cells (CSCs). Conceptually, CSCs that evade intensive multimodal therapy dictates tumor progression, relapse/recurrence and poor clinical outcomes. Herein, we investigated the plasticity and stem-cell related molecular response of aggressive metastatic neuroblastoma cells that fits CSC model. Well characterized clones of ‘metastatic site derive aggressive cells’ (MSDACs) from the manifold of metastatic tumors of clinically translatable HR-NB were characterized for their CSC fit. Alternated, yet stabilized (three generations) microenvironment simulation experiments with ‘serum-free stem cell medium’ to ‘growth medium with serum’ and vice versa identified flexible revocable plasticity. Signatures stem-cell related molecular responses consistent with phenotypic conversions are observed. Successive reintroduction to the favorable niche not only regained identical EMT, self-renewal capacity, pluripotency maintenance, and other stem-cell related signaling events, but also instigated additional events depicting the aggressive adaptive plasticity. Together, these results demonstrated the flexible plasticity of HR-NB MSDACs that typically fits in CSC model and further identified the intrinsic adaptivness of the successive phenotype switching that clarify the heterogeneity of HR-NB. Moreover, the continuous ongoing acquisition of stem-cell related molecular rearrangements may hold the key for the switch from favorable disease to HR-NB. Citation Format: Satish Kumar Ramraj, Faizan H. Khan, Sheeja Aravindan, Mohan Natarajan, Terence S. Herman, Natarajan Aravindan. Metastatic neuroblastoma cancer stem cells exhibit flexible plasticity and adaptive stemness signaling. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1398. doi:10.1158/1538-7445.AM2015-1398

Lipid rafts signaling detected by FRET-based molecular biosensors

Cells recognize and process various extracellular signals via transmembrane receptors and membrane-associated signaling molecules. Therefore, the precise regulation of these signaling events at the plasma membrane, which occur spatiotemporally, is necessary for proper cellular functions such as cell proliferation, migration, and survival. The plasma membrane may contain dynamic microdomains called lipid rafts, which are suggested to be crucial for the regulation of efficient and specific signaling pathways. However, because of the limitation in methodologies, the specific molecular mechanisms underlying dynamic signaling events at lipid rafts are largely unknown. This review discusses the traditional biochemical methods for the visualization of lipid rafts and the related signaling events at these microdomains. In addition, the review reports on fluorescence resonance energy transfer (FRET)-based molecular biosensors with lipid rafts targeting sequences as a powerful tool for live-cell imaging of spatiotemporal signaling events at lipid rafts. In particular, examples of dynamic lipid rafts signaling mechanisms visualized by FRET-based biosensors in live cells are covered in the last section.

Sortilin mediates the release and transfer of exosomes in human lung cancer A549 cells

The transfer of exosomes containing both genetic and protein materials is necessary for the control of cancer cell microenvironment to promote tumor angiogenesis. The nature and function of proteins found in the exosomal cargo, their mechanisms in membrane transport and related signaling events are not clearly understood. The multifaceted receptor, neurotensin (NT) receptor-3, also called sortilin plays a multitude of roles in the cell as a receptor or a co-receptor, in protein transport to the plasma membrane and to lysosomes, and in the regulated secretion. Numerous studies indicate that sortilin expression is elevated in several human cancers. These same reports suggested that NT mediated by sortilin stimulated by an autocrine/paracrine function could be a mechanism associated with the tumorigenesis. In this study, we demonstrate in human lung cancer A549 cells, that the exosome release mechanism is closely linked to a multifaceted receptor, neurotensin (NT) receptor-3 also called sortilin. Sortilin is already known to be important for cancer cell function. We report for the first time its role in the assembly of a tyrosine kinase complex and subsequent exosome release. This novel complex (TES complex) found in exosomes results in the linkage of two tyrosine kinase receptors, TrkB and EGFR with sortilin. Using in vitro models, we demonstrate that this complex containing sortilin exhibits a control on endothelial cells and angiogenesis activation through exosome transfer. We show for the first time, a new role for sortilin in the release and the assembly TES complex in lung cancer cells. Our data suggest a paracrine function for sortilin and its partners in exosome transfer and the control of the microenvironment. This novel complex containing sortilin could act as a molecular switch in cancer progression by promoting angiogenesis.

Ca2+‐related signaling events influence TLR9‐induced IL‐10 secretion in human B cells

Suppressory B-cell function controls immune responses and is mainly dependent on IL-10 secretion. Pharmacological manipulation of B-cell-specific IL-10 synthesis could, thus, be therapeutically useful in B-cell chronic lymphocytic leukemia, transplantation, autoimmunity and sepsis. TLR are thought to play a protagonistic role in the formation of IL-10-secreting B cells. The aim of the study was to identify the molecular events selectively driving IL-10 production in TLR9-stimulated human B cells. Our data highlight the selectivity of calcineurin inhibitors in blocking TLR9-induced B-cell-derived IL-10 transcription and secretion, while IL-6 transcription and release, B-cell proliferation, and differentiation remain unaffected. Nevertheless, TLR9-induced IL-10 production was found to be independent of calcineurin phosphatase activity and was even negatively regulated by NFAT. In contrast to TLR9-induced IL-6, IL-10 secretion was highly sensitive to targeting of spleen tyrosine kinase (syk) and Bruton's tyrosine kinase. Further analyses demonstrated increased phosphorylation of Ca(2+) /calmodulin kinase II (CaMKII) in TLR9-stimulated B cells and selective reduction of TLR9-induced secretion of IL-10 upon treatment with CaMKII inhibitors, with negligible impact on IL-6 levels. Altogether, our results identify calcineurin antagonists as selective inhibitors of IL-10 transcription and syk/Bruton´s tyrosine kinase-induced Ca(2+) /calmodulin- and CaMKII-dependent signaling as a pathway regulating the release of TLR9-induced B-cell-derived IL-10.

Sortilin mediates the release and transfer of exosomes in concert with two tyrosine kinase receptors.

The transfer of exosomes containing both genetic and protein materials is necessary for the control of the cancer cell microenvironment to promote tumor angiogenesis. The nature and function of proteins found in the exosomal cargo, and the mechanism of their action in membrane transport and related signaling events are not clearly understood. In this study, we demonstrate, in human lung cancer A549 cells, that the exosome release mechanism is closely linked to the multifaceted receptor sortilin (also called neurotensin receptor 3). Sortilin is already known to be important for cancer cell function. Here, we report for the first time its role in the assembly of a tyrosine kinase complex and subsequent exosome release. This new complex (termed the TES complex) is found in exosomes and results in the linkage of the two tyrosine kinase receptors TrkB (also known as NTRK2) and EGFR with sortilin. Using in vitro models, we demonstrate that this sortilin-containing complex exhibits a control on endothelial cells and angiogenesis activation through exosome transfer.

Critical roles for Akt kinase in controlling HIV envelope-mediated depletion of CD4 T cells

BackgroundThe cell surface receptors CD4 and CCR5 bind CCR5-tropic HIV Envelope (Env) glycoprotein during virus attachment. These same receptors have signaling activities related to normal immune cell functions. We also know that Env binds to CCR5 present at high levels on CD4-negative γδ T cells where it signals through p38 MAP kinase to activate caspases and Fas-independent cell death. Here, we asked whether Env signaling through cellular receptors is responsible for death among uninfected CD4+/CCR5+ T cells and what are the effects of Env on CD4+/CCR5-negative cells that might impact HIV infection. The outcomes of Env binding are analyzed in terms of signal transduction and the effects on cell activation or cell death pathways.ResultsEnv binding to CD4 signals through Erk and Akt kinases. Activation of Erk/Akt suppresses p38 due to CCR5 binding, and allows cell survival. When CD4 signaling was blocked by soluble CD4 or protein kinase inhibitors, p38 activation and Fas-independent cell death were increased among uninfected CD4+ CCR5+ T cells. We also noted specific effects of CD4 signaling on CCR5-negative CD4 T cells in tonsil lymphocyte cultures. Exposure to CCR5-tropic HIV Env (BaL strain) increased expression of CXCR5, PD-1, Fas and FasL. Among CD4+/CCR5- T cells expressing high levels of CXCR5 and PD-1, there were substantial amounts of Fas-dependent cell death. Increased CXCR5 and PD-1 expression was blocked by soluble CD4 or specific inhibitors of the Akt kinase, showing a direct relationship between CD4 signaling, T cell activation and Fas-dependent cell death.ConclusionsSpecific inhibition of Akt activation increased Env-dependent cell death of CCR5+ CD4 T cells. The same inhibitor, antibodies blocking the CD4 binding site on gp120, or soluble CD4 also prevented the increase in expression of CXCR5 or PD-1, and reduced the levels of Fas-dependent cell death. The Akt kinase and related signaling events, are key to cell survival that is needed for productive infection, and may be targets for the development of antivirals. Specific inhibitors of Akt would decrease productive infection, by favoring cell death during virus attachment to CD4+ CCR5+ target cells, and reduce immune activation to prevent Fas-dependent death of uninfected CXCR5+ PD-1+ CD4 T cells including T follicular helper cells that share this phenotype.

Investigating Cell-ECM Contact Changes in Response to Hypoosmotic Stimulation of Hepatocytes In Vivo with DW-RICM

Hepatocyte volume regulation has been shown to play an important role in cellular metabolism, proliferation, viability and especially in hepatic functions such as bile formation and proteolysis. Recent studies on liver explants led to the assumption that cell volume changes present a trigger for outside-in signaling via integrins, a protein family involved in mediating cellular response to binding to the extracellular matrix (ECM). However, it remains elusive how these volume change related signaling events are transducted on a single cell level and how these events are influenced and controlled by ECM interactions. One could speculate that an increase in cell volume leads to an increase in integrin/ECM contacts which causes activation of integrins, which act as mechano-sensors. In order to test this idea, it was an important issue to quantify the cell volume-dependence of the contact areas between the cell and the surrounding ECM. In this study we used two wavelength reflection interference contrast microscopy (DW-RICM) to directly observe the dynamics of cell-substrate contacts, mimicking cell-ECM interactions, in response to a controlled and well-defined volume change induced by hypoosmotic stimulation. This is the first time a non-invasive, label-free method is used to uncover a volume change related response of in vitro hepatocytes in real time. The cell cluster analysis we present here agrees well with previous studies on ex vivo whole liver explants. Moreover, we show that the increase in contact area after cell swelling is a reversible process, while the reorganisation of contacts depends on the type of ECM molecules presented to the cells. As our method complements common whole liver studies providing additional insight on a cell cluster level, we expect this technique to be particular suitable for further detailed studies of osmotic stimulation not only in hepatocytes, but also other cell types.

Functional significance of CD44 and MMP‐9 in cartilage homeostasis

Previous reports have proposed a mechanistic link between the CD44 cell surface receptor and the matrix metalloproteinase (MMP)‐9 in tumor invasion, prostate cancer progression and osteoclast migration. CD44 is expressed by articular chondrocytes and interestingly during the progression of osteoarthritis (OA) CD44 fragmentation occurs, resulting in a reduction in hyaluronan (HA) binding capacity. Furthermore, both treatment with the inflammatory cytokine and catabolic agent IL‐1β, as well as disruption of CD44‐HA interactions result in stimulation of MMP‐9. Thus, the purpose of this study is to determine CD44‐dependent, MMP‐9 related signaling events with the goal of identifying novel OA therapeutic targets. Primary chondrocytes and femoral heads were isolated from 7–14 day old BALB/c wild‐type (WT) and CD44 knock‐out (KO) mice. Treatment with IL‐1β showed a loss in safranin O staining of the extracellular matrix only in treated femoral heads from WT mice. Immunoblot analysis and zymography revealed that MMP‐9 expression and gelatinase activity is higher in chondrocytes obtained from WT mice that were treated with IL‐1β versus CD44 KO IL‐1β‐treated cells. Taken together, these studies suggest a functional link between CD44 expression status, cell associated HA and MMP‐9 activity in cartilage. Supported by NIH R01‐AR39507 and R01‐AR43384.

Reduced expression of tryptophan hydroxylase in the prefrontal cortex of a parkinsonian mouse model

OBJECTIVEIn 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP)‐treated mouse model of Parkinson's disease (PD), we have shown a significant decrease in the density of beaded type serotonin (5‐HT) axons and concentrations of 5‐HT in the prefrontal cortex (PFC). Here we studied the protein level of tryptophan hydroxylase (TPH) and beta arrestin (βAR) 1 and 2 in the PFC in MPTP treated mice.DESIGN AND METHODSMale C57BL/6J mice were treated with 4 doses of MPTP 20 mg/kg (i.p.) at every 2 hours and sacrificed after 3 and 16 weeks. The protein expression for TPH, βAR‐1 and ‐2 in the PFC and TPH in the raphe was studied by Western blot. 5‐HT cell bodies in the raphe were studied by immunohistochemistry.RESULTSMPTP‐treated mice have shown a significant decrease in TPH protein level in PFC and a significant increase in the raphe nucleus. Protein expression for β‐AR1 and β‐AR2 were also significantly decreased in PFC. Immunohistochemistry of 5‐HT neurons in the raphe nuclei with TPH antibodies showed reduced intensity of staining for 5‐HT cell bodies in medial raphe (MR) and slightly increased in dorsal raphe (DR) after MPTP treatment. The reduced density of TPH‐labeled 5‐HT neurons in the MR correlated well with our earlier report of preferential decrease in the density of thick beaded 5‐HT axons in the PFC which originate from MR.CONCLUSIONThese results suggest that TPH is a major target of MPTP‐induced alterations of serotonergic function in PFC with a possible link to depression. Targeting TPH and related signaling events may afford therapeutic advantages for the management of depression in PD. Supported by NIH SNRP/NINDS grant NS041071.

Low Concentrations of Salicylic Acid Stimulate Insect Elicitor Responses in Zea mays Seedlings

Salicylic acid (SA) generally is thought to suppress jasmonic acid (JA) related signaling events. However, when we treated the roots of corn seedlings overnight with low physiological concentrations of SA (50 μM), we found a priming effect of this pretreatment on typical insect elicitor (IE)-induced responses in the leaves of these plants. IE-induced JA was more than 2-fold up regulated in SA-pretreated plants. Consequently, IE-induced volatile organic compounds (VOC) release also was significantly increased. In contrast, when corn seedlings were treated with SA overnight and then mechanically damaged, we found no significant differences in JA accumulation. We also found that the application of even lower concentrations of SA (5 μM) had no significant effect on IE-induced responses, while higher concentrations (500 μM) inhibited IE-induced JA accumulation. Likewise, shorter exposure to SA did not affect subsequent JA accumulation induced by IE or mechanical wounding. These results provide evidence for the existence of non-compatible defense priming by signaling molecules that usually are involved in a conflictive defense signaling pathway and suggests common elements in the regulation of priming plant defense responses.