Gly Response Research Articles

QKI deficiency maintains glioma stem cell stemness by activating the SHH/GLI1 signaling pathway.

Glioblastoma (GBM) stem cells (GSCs) have been found to be the main cause of malignant GBM progression. It has also been found that Quaking homolog (QKI) plays a predominant role in driving GBM development. Here, we aimed to asses the role of QKI in maintaining GSC stemness and inducing the invasiveness of GBM cells. Public databases were used to assess the expression of QKI and its correlation with stemness markers in primary GBMs. The CRISPR-Cas9 technology was used to generate QKI knockout GBM cells, and RNA immunoprecipitation was used to assess QKI-GLI1 protein-mRNA interactions. In addition, in vitro and in vivo GBM cell proliferation, migration, xenografting and neurosphere formation assays were performed. Using public GBM databases, QKI was identified as a potential GSC regulator. We found that QKI could inhibit stem-like cell (SLC) stemness and prolong the survival of xenografted mice. Mechanistically, we found that QKI knockout increased the GLI Family Zinc Finger 1 (GLI1) mRNA level, which is essential for maintaining the self-renewal ability of GSCs. In addition, we found that QKI knockout activated the Hedgehog signaling pathway via Tra-2 and GLI response element (TGE)-specific GLI1 mRNA disruption. Our data indicate that upregulation of GLI1 induced by QKI deficiency maintains GSC stemness and enhances the invasiveness of GBM cells, thereby hinting at new options for the treatment of GBM.

Abstract 1308: ERRβ ligand DY131 regulation of the hedgehog signaling pathway by modulation of Akt phosphorylation.

Abstract Nuclear receptor family member, Estrogen Related Receptor β (ERRβ), and hedgehog (Hh)-signaling are reported to be significant for both tumorigenesis and stem cell maintenance. ERRβ itself is a crucial factor in inducing pluripotent stem cells. Here we investigate the hypothesis that ERRβ can interact with Hh signaling pathway, and modulation of ERRβ can influence Hh signaling. NIH3T3 and HEK293 cells, transfected with a Gli response element driven luciferase reporter, were treated with different concentrations of DY131, a synthetic ERRβ ligand, in the presence or absence of exogenous ERRβ. We monitored the Gli reporter activity, as well as Gli1, Akt and phosphorylated Akt via western blot. Results: We found that DY131 inhibited Hh signaling activity when the pathway was activated by hedgehog peptide-conditioned medium, or the Smoothened Agonist (SAG), with an IC50 of 500nM. We also found that in HEK293 cells, where Gli reporter activity cannot be activated by either conditioned medium or SAG, DY131 dose dependently increased both endogenous and exogenous Gli1-induced reporter activity up to 4 fold. In addition, the transfection of ERRβ potentiated DY131’s effect on Gli reporter activity up to 7 fold. Western blot results, which are consistent with Gli reporter activity in both cell lines, showed that when Hh signaling is activated by Hedgehog peptide-conditioned medium, DY131 decreased Gli1 protein concentration; however when Hh signaling is not activated by conditioned medium, DY131 increases the concentration of Gli1 protein. Phosphorylated Akt, which is a non-canonical activator of Gli1, is up-regulated when Gli1 concentration increases, and down-regulated when the cells are treated with DY131. Conclusion: Our results suggest a new level of regulation by ERRβ on the Hh-signaling pathway. ERRβ, induced by DY131, can modulate Akt's regulation of Gli1. Additionally, our results indicate that modulation of ERRβ, via ERRβ selective drugs like DY131, may serve as a new target for Hh-driven cancer treatment. Citation Format: Yuan Lu, Benjamin R. Merideth, Hui Lin, Dennis B. Lubahn. ERRβ ligand DY131 regulation of the hedgehog signaling pathway by modulation of Akt phosphorylation. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1308. doi:10.1158/1538-7445.AM2013-1308

Abstract 1998: Inhibition of hedgehog signaling in prostate cancer by extracts of Sutherlandia

Abstract Prostate cancer possesses long latency periods and is responsive to dietary mediators, making it a target for phytochemoprevention. Many botanical compounds that have been proposed to prevent cancer may potentially work via inhibition of the hedgehog signaling pathway. Here we investigated the potential of Sutherlandia frutescens (also called Lessertia and “cancer bush” in South Africa) to inhibit hedgehog signaling. We hypothesize that the anti-cancer effects of Sutherlandia are due to its inhibition of hedgehog signaling pathway activity. Methods: We evaluated Sutherlandia's effects of growth inhibition in vitro both in the human prostate cancer cell line PC3 and mouse prostate cancer cell line TRAMP-C2 by exposing the cells for 72hrs to plant extracts before protein concentrations were measured to evaluate inhibition of growth. To determine hedgehog pathway inhibitory activity, we treated two different cell lines (an NIH3T3 cell line and a TRAMPC2 cell line) stably transfected with a firefly luciferase reporter having Gli response elements in the firefly luciferase promoter. After 48hr exposure to treatment with multiple doses of Sutherlandia, a firefly substrate was added to the cell lysate and the luciferase signal was measured using a Biotek Synergy plate reader. Finally, Sutherlandia was incorporated into a diet and fed to TRAMP (Transgenic Adenocarcinoma Mouse Prostate) mice to examine whether the plant can delay or even inhibit prostate cancer incidence in the TRAMPmouse model. Results: Sutherlandia extracts inhibited growth of both PC3 and TRAMPC2 cells. In addition, hedgehog signaling was inhibited by Sutherlandia in both NIH3T3 and TRAMPC2 reporter cells. Interestingly, in vivo the lowest concentration of Sutherlandia diet had the greatest effect on inhibition of poorly differentiated adenocarcinoma in the TRAMP mice. Conclusions: Sutherlandia's inhibition of prostate cancer growth may be via inhibition of hedgehog signaling. Future work to identify in Sutherlandia the active compound having this effect, and the ideal concentration for use in vivo may lead to a means whereby dietary intervention for prostate cancer prevention and/or treatment is possible. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1998. doi:1538-7445.AM2012-1998

Sonic Hedgehog Pathway Activation Is Induced by Acute Brain Injury and Regulated by Injury-Related Inflammation

The adult mammalian brain responds to injury by activating a program of cell proliferation during which many oligodendrocyte precursors, microglia, and some astrocytes proliferate. Another common response to brain injury is the induction of reactive gliosis, a process whereby dormant astrocytes undergo morphological changes and alter their transcriptional profiles. Although brain injury-induced reactive gliosis is concurrent with the proliferation of surrounding cells, a functional relationship between reactive gliosis and this cell proliferation has not been clearly demonstrated. Here, we show that the mitogen sonic hedgehog (SHH) is produced in reactive astrocytes after injury to the cerebral cortex and participates in regulating the proliferation of Olig2-expressing (Olig2(+)) cells after brain injury. Using a cortical freeze injury to induce reactive gliosis in a Gli-luciferase reporter mouse, we show that the SHH pathway is maximally active 3 d after brain injury and returns to baseline levels by 14 d. SHH expression parallels Gli activation and localizes to glial fibrillary acidic protein-expressing reactive astrocytes. Inhibition of the SHH pathway with cyclopamine blocks the Gli response and significantly reduces both the proliferating and overall number of Olig2(+) cells in the injured cortex. To provide mechanistic insight into SHH pathway activation in astrocytes, we show that proinflammatory stimuli activate SHH-expressing reactive astrocytes, whereas inhibition of inflammation-induced reactive gliosis by macrophage depletion abolishes SHH activation after brain injury and dampens cell proliferation after injury. Our data describes a unique reactive astrocyte-based, SHH-expressing niche formed in response to injury and inflammation that regulates the proliferation of Olig2(+) cells.

A dynamic Gli code interprets Hh signals to regulate induction, patterning, and endocrine cell specification in the zebrafish pituitary

Hedgehog (Hh) signaling is necessary for the induction and functional patterning of the pituitary placode, however the mechanisms by which Hh signals are interpreted by placodal cells are unknown. Here we show distinct temporal requirements for Hh signaling in endocrine cell differentiation and describe a dynamic Gli transcriptional response code that interprets these Hh signals within the developing adenohypophysis. Gli1 is required for the differentiation of selected endocrine cell types and acts as the major activator of Hh-mediated pituitary induction, while Gli2a and Gli2b contribute more minor activator functions. Intriguingly, this Gli response code changes as development proceeds. Gli1 continues to be required for the activation of the Hh response anteriorly in the pars distalis. In contrast, Gli2b is required to repress Hh target gene expression posteriorly in the pars intermedia. Consistent with these changing roles, gli1, gli2a, and gli2b, but not gli3, are expressed in pituitary precursor cells at the anterior neural ridge. Later in development, gli1 expression is maintained throughout the adenohypophysis while gli2a and gli2b expression are restricted to the pars intermedia. Given the link between Hh signaling and pituitary adenomas in humans, our data suggest misregulation of Gli function may contribute to these common pituitary tumors.

The General Anesthetic Pentobarbital Slows Desensitization and Deactivation of the Glycine Receptor in the Rat Spinal Dorsal Horn Neurons

Although many general anesthetics have been found to produce anesthetic and analgesic effects by augmenting GABA(A) receptor (GABA(A)R) function, the role of the glycine receptor (GlyR) in this process is not fully understood at the neuronal level in the spinal cord. We investigated the effects of a barbiturate general anesthetic, pentobarbital (PB), on the glycinergic miniature inhibitory postsynaptic currents (mIPSCs) and the responses to exogenously applied glycine, or taurine, a low affinity GlyR agonist, by using the whole-cell patch-clamp technique in the rat spinal dorsal horn neurons isolated using a novel mechanical method. Bath application of 30 microm PB significantly prolonged the decay time constant of the spontaneous glycinergic mIPSC without changing its amplitude and frequency. Co-application of 0.3 mm PB reduced the peak amplitude, affected the macroscopic desensitization and deactivation of the response to externally applied Gly in a concentration-dependent manner. In addition, the recovery of Gly response from desensitization was also prolonged by PB. However, PB did not change the desensitization and deactivation kinetics of the taurine-induced response. The GABA(A)R antagonist bicuculline (10 microm) did not affect the effect of PB on the Gly response. Thus, PB prolonged the spinal glycinergic mIPSCs by slowing desensitization and deactivation of GlyR. Two other structurally different intravenous anesthetics, i.e. propofol (10 microm) and etomidate (3 microm), prolonged the duration of the glycinergic mIPSC in the rat spinal dorsal horn neurons. In conclusion, on GlyR-Cl(-) channel complexes there may exist action site(s) of intravenous general anesthetics. GlyR and glycinergic neurotransmission may play an important role in the modulation of general anesthesia in the mammalian spinal cord.

State-dependent cross-inhibition between anionic GABAA and glycine ionotropic receptors in rat hippocampal CA1 neurons

Using whole-cell patch-clamp recording of acutely isolated rat hippocampal CA1 neurons, we studied the state-dependent cross-inhibition between anionic GABA(A) and glycine (Gly) ionotropic receptors. Co-application of relatively high concentrations of GABA and Gly produced a total current (IGABA + Gly) much smaller than the linear summation of the two individual responses. The mutual inhibition between IGABA and IGly was voltage-independent. However, no current inhibition was observed with co-application of low concentrations of these two agonists. The hippocampal neurons lacking Gly response (IGly) showed no current inhibition with GABA current (IGABA), whereas the neurons losing GABA response (IGABA) (after complete rundown of IGABA) showed no current inhibition with IGly. The current inhibition was also absent in the presence of Gly or GABA(A) receptor antagonists, strychnine or bicuculline, respectively. The results indicate that cross-inhibition between GABA(A) and Gly receptors is state-dependent and a direct receptor-receptor interaction might enable the cross-inhibition to occur.

Mediation of Sonic hedgehog-induced expression of COUP-TFII by a protein phosphatase.

A Sonic hedgehog (Shh) response element was identified in the chicken ovalbumin upstream promoter-transcription factor II (COUP-TFII) promoter that binds to a factor distinct from Gli, a gene known to mediate Shh signaling. Although this binding activity is specifically stimulated by Shh-N (amino-terminal signaling domain), it can also be unmasked with protein phosphatase treatment in the mouse cell line P19, and induction by Shh-N can be blocked by phosphatase inhibitors. Thus, Shh-N signaling may result in dephosphorylation of a target factor that is required for activation of COUP-TFII-, Islet1-, and Gli response element-dependent gene expression. This finding identifies another step in the Shh-N signaling pathway.

Protein kinase C-mediated enhancement of glycine response in rat sacral dorsal commissural neurones by serotonin.

1. The modulatory effect of serotonin (5-hydroxytryptamine, 5-HT), on the glycine (Gly) response was investigated in neurones acutely dissociated from the rat sacral dorsal commissural nucleus (SDCN) using a nystatin-perforated patch recording configuration. 2. 5-HT potentiated the 10(-5) M Gly-induced Cl- current (IGly) in a concentration-dependent manner without changing the reversal potential of the Gly response or the affinity of Gly to its receptor. 3. alpha-Methyl-5-HT mimicked and ketanserine blocked the 5-HT action on IGly, thus indicating the 5-HT2 receptor-mediated enhancement. 4. Phorbol-12-myristate-13-acetate and 1-oleoyl-2-acetylglycerol potentiated IGly. The subsequent application of 5-HT slightly increase IGly. Chelerythrine blocked the enhancement of IGly by 5-HT, thus suggesting the involvement of protein kinase C (PKC) in the pathway of 5-HT action on IGly. 5. Pertussis toxin (IAP) treatment did not block the facilitatory effect of 5-HT on IGly. 6. BAPTA AM did not disturb the 5-HT-induced potentiation of IGly, thus suggesting that [Ca2+]i is not involved in the 5-HT effect. 7. In conclusion, activation of a 5-HT2 receptor coupled to an IAP-insensitive G-protein increases intracellular diacylglycerol (DAG) formation. The accumulation of DAG also increases the Ca(2+)-independent PKC activity, thus resulting in the potentiation of the Gly response in the SDCN neurones.

Modulation of glycine-induced chloride current in acutely dissociated rat periaqueductal gray neurons by μ-opioid agonist, DAGO

Effect of a μ-opioid agonist ( d -Ala 2 , N -McPhe 4 ,Gly 5 -ol-enkephalin, DAGO), on glycine (Gly)-induced chloride current ( I Gly ) was investigated in the periaqueductal gray (PAG) neurons acutely dissociated 1–2-week-old Wistar rats by the use of nystatin-perforated patch recording configuration under voltage-clamp condition. At a holding potential ( V H ) of −40 mV, DAGO caused a sustained potentiation of I Gly at the low concentrations (10 −6 -10 −5 M) but reduced slightly the Gly response at the high concentration (10 −4 M). The reversal potential of I Gly was equal to the Cl − equilibrium potential ( E Cl ) and was not changed in the presence of 10 −6 M DAGO. The 10 −5 M Gly response was inhibited by the simultaneous treatment of forskolin and 3-isobutyl-l-methylxanthine (IBMX). H-89, a protein kinase A (PKA) inhibitor, increased the 10 −5 M Gly response but had little effect on the 10 −4 M Gly response. DAGO increased 10 −5 M Gly response in the presence of forskolin and IBMX but, not more than in the absence of forskolin and IBMX. The 10 −5 M Gly response augumented by DAGO was not affected by adding H-89. The present results suggest that the glycine-induced chloride current is cAMP dependent and is inhibited by PKA, and that the potentiation of the glycine response by DAGO is also cAMP dependent and is due to the inhibition of PKA as that of H-89. We conclude that the potentiation of glycine response by DAGO is mediated by an inhibition of cAMP-dependent PKA in the PAG neurons.

Modulation of glycine-induced chloride current in acutely dissociated rat periaqueductal gray neurons by μ-opioid agonist, DAGO

Effect of a μ-opioid agonist (d-Ala2,N-McPhe4,Gly5-ol-enkephalin, DAGO), on glycine (Gly)-induced chloride current (IGly ) was investigated in the periaqueductal gray (PAG) neurons acutely dissociated 1–2-week-old Wistar rats by the use of nystatin-perforated patch recording configuration under voltage-clamp condition. At a holding potential (VH ) of −40 mV, DAGO caused a sustained potentiation ofIGly at the low concentrations (10−6-10−5 M) but reduced slightly the Gly response at the high concentration (10−4 M). The reversal potential ofIGly was equal to the Cl− equilibrium potential (ECl) and was not changed in the presence of 10−6 M DAGO. The 10−5 M Gly response was inhibited by the simultaneous treatment of forskolin and 3-isobutyl-l-methylxanthine (IBMX). H-89, a protein kinase A (PKA) inhibitor, increased the 10−5 M Gly response but had little effect on the 10−4 M Gly response. DAGO increased 10−5 M Gly response in the presence of forskolin and IBMX but, not more than in the absence of forskolin and IBMX. The 10−5 M Gly response augumented by DAGO was not affected by adding H-89. The present results suggest that the glycine-induced chloride current is cAMP dependent and is inhibited by PKA, and that the potentiation of the glycine response by DAGO is also cAMP dependent and is due to the inhibition of PKA as that of H-89. We conclude that the potentiation of glycine response by DAGO is mediated by an inhibition of cAMP-dependent PKA in the PAG neurons.

Physiological roles of glycine and γ-aminobutyric acid in dissociated neurons of rat visual cortex

The effects of glycine (Gly) and γ-aminobutyric acid (GABA) on the neurons acutely dissociated from rat visual cortex (VC) were investigated in the whole-cell mode using a conventional patch-clamp technique. GABA and Gly evoked Cl − currents (I Cl) in a concentration-dependent manner at a holding potential (V H) of −50 mV. The half maximum effective concentrations (EC 50) were 4.64 × 10 −6 M for GABA and 6.67 × 10 −5 M for Gly. Strychnine and bicuculline reversively inhibited both 10 −5 M GABA -and 10 −4 M Gly-induced I Cl in a concentration-dependent manner. The half maximum inhibitory concentrations (IC 50) of strychnine on GABA- and Gly-induced currents were 4.00 × 10 −6 M and 8.26 × 10 −8 M, respectively. The IC 50 values of bicuculline on GABA and Gly responses were 1.18 × 10 −6 M and 2.97 × 10 −4 , respectively. GABA at 10 −5 M, which is near the EC 50 of the GABA response, induced I Cl in all neurons tested n = 83). However, Gly of 10 −4 M, which is near the the Gly response, induced I Cl in 34 out of 83 neurons tested (41%). Moreover, the maximum amplitude of the Gly response was about 60% of that of the GABA response. On the other hand, the enhancement of N-methyl- d-aspartate (NMDA, 3 × 10 −4M ) response by Gly (10 −6 M) was observed in all neurons (n=36) whether they had the Gly-induced I Cl or not. In conclusion, it was proved that the VC neurons of immature rat could be classified into two classes, i.e. Gly sensitive and Gly insensitive in respect to activation of Cl − channels. There were no significant correlations between the Gly response and the facilitatory action of Gly on the NMDA response, nor between the Gly and GABA responses. The GABA response was closely correlated to the NMDA response, having a correlation coefficient of 0.86.

Glycine response in isolated dorsal cochlear nucleus of C57BL/6J mouse

Pharmacological properties of glycine (Gly)-induced Cl − current (I Cl) in the dorsal cochlear nucleus (DCN) neurons acutely dissociated from C57BL/6J mouse were investigated in the whole-cell configuration of the patch-clamp technique. Gly-induced I Cl increased in a sigmoidal manner with higher Gly concentrations. Strychnine blocked the Gly response competitively at low and non-competitively at high concentrations. Both glutamate (Glu) and N-methyl- d-aspartate (NMDA) responses were augmented by adding 10 −6 M Gly, at which concentration Gly did not induce any I Cl. This facilitation was not affected by strychnine. Our results clearly show the existence of strychnine-sensitive and -insensitive glycine receptors in the DCN neurons.

Synaptic responses of guinea pig and rat central amygdala neurons in vitro

1. To investigate postsynaptic potentials (PSPs), we made intracellular recordings from neurons of the amygdaloid central nucleus in slices from the guinea pig and rat brains maintained in vitro. The results from guinea pigs and rats were very similar. 2. In the presence of bicuculline (20 microM), focal electrical stimulation of the amygdaloid basal nucleus with low intensities elicited short-latency excitatory PSPs (EPSPs) followed by long-latency EPSPs. The short-latency EPSP was selectively blocked by 6-cyano-7-nitroquinoxaline-2,3-dion (CNQX; 10-20 microM). The long-latency EPSP was preferentially abolished by D,L-2-amino-5-phosphonovaleric acid (D,L-APV; 40 microM) and was augmented by removal of extracellular Mg2+. The compound EPSP reversed at -4 mV, which was close to -1 mV, the reversal potential for pressure-ejected glutamate (Glu). 3. When the intensity of the focal stimulation was increased in the presence of bicuculline (20 microM), CNQX (20 microM), and D,L-APV (50 microM), a second EPSP with a short latency and a prolonged duration could be evoked in approximately 65% of the neurons. The EPSPs were reversibly blocked by d-tubocurarine (50 microM) or hexamethonium (200 microM) but were unaffected by atropine (1 microM) or a 5-hydroxytryptamine type 3 receptor antagonist, ICS-205930 (5-10 microM). In these neurons, acetylcholine (ACh; 1-3 mM) caused a depolarization, associated with a decreased input resistance. 4. In the presence of CNQX (20 microM) and D,L-APV (50 microM), single focal stimulation of the dorsolateral subdivision in the central nucleus with low intensities elicited a depolarizing inhibitory PSP (IPSP). The IPSP was reversibly abolished by bicuculline (20-40 microM). The reversal potential (-63 mV) for the IPSP was similar to the reversal potential (-61 mV) for the response to gamma-aminobutyric acid (GABA) applied by pressure ejection. 5. In the presence of bicuculline (20-40 microM) and CNQX (20 microM), a repetitive focal stimulus with high intensities delivered to the dorsolateral subdivision produced a hyperpolarizing PSP followed by a slow depolarization in most neurons. Of putative inhibitory amino acid transmitters, glycine (Gly; 3 mM) produced only a hyperpolarization, associated with a decrease in input resistance. Strychnine (1-2 microM) reversibly blocked both the Gly hyperpolarization and the synaptically evoked hyperpolarization. The reversal potential of -81 mV for the hyperpolarizing PSP was close to -82 mV for the Gly hyperpolarization. The reversal potential for the Gly response was shifted to less negative values by increasing the external K+ concentration or decreasing the extracellular Cl- concentration.(ABSTRACT TRUNCATED AT 400 WORDS)

Decrease in blood glucose and release of gut glucagon-like immunoreactive materials by bombesin infusion in the dog.

Synthetic bombesin (100 ng/min) was infused under pentobarbital anesthesia in normal dogs and in insulin deprived depancreatized dogs 4 days after surgery. The release of gut glucagon-like immunoreactive materials (gut GLI) calculated as the difference between the values measured using cross-reacting antiserum and a so-called pancreatic glucagon specific antiserum was markedly stimulated by bombesin infusion. Plasma glucagon immunoreactivity (GI) measured by pancreatic glucagon specific antiserum also showed a small increase, whereas plasma glucose decreased significantly with a transient rise in insulin. The plasma glucose level did not decrease in depancreatized dogs. Gut GLI response in the regional mesenteric vein to 5% glucose administered into the loop of the ileum was strongly augmented by bombesin infusion. It is concluded that (1) bombesin infusion decreased blood glucose level in normal dogs but not in depancreatized dogs. (2) Bombesin infusion markedly augmented the release of GLI from the intestine. (3) Bombesin also stimulated the release of glucagon which was probably of gastrointestinal origin. (4) Insulin release was stimulated transiently by bombesin infusion. Thus, a competition of gut GLI with glucagon at the glucagon receptor site may be an explanation of the reduction in blood glucose.

The effect of somatostatin on the response of GLI to the intraduodenal administration of glucose, protein, and fat.

The effects of somatostatin on GLI release during the absorption of intraduodenally administered glucose, casein hydrolysate and longchain triglycerides were studied in conscious dogs. Whereas, after an intraduodenal glucose load, GLI rose promptly in saline-infused control experiments to a peak of 5 ng/ml (SEM +/- 4) in 60 minutes, significantly lower values were observed during somatostatin infusion (P less than 0.025 -- 0.05). A similar reduction in the magnitude of the GLI response to intraduodenally administered casein hydrolysate (P less than 0.05) and fat (p less than 0.05) was observed.