Cannabinoid 1 Receptor and Interleukin-6 Receptor Together Induce Integration of Protein Kinase and Transcription Factor Signaling to Trigger Neurite Outgrowth
ABSTRACT Activation of the G(o/i)-coupled cannabinoid 1 receptor (CB1R) has been shown to induce neurite outgrowth in Neuro2A cells through activation of Src kinase and STAT3 transcription factor. Signaling by the interleukin 6 receptor (IL-6R) also activates STAT3 through Jak kinase. We studied if signals from the two pathways could be integrated in a synergistic manner to trigger neurite outgrowth in Neuro2A cells. At low concentrations, when agonist at either receptor by itself has no effect, we found that CB1R and IL-6R stimulation together induced synergistic neurite outgrowth. Signal integration requires activation of transcription factors by Src, Jak, and mitogen-activated protein kinases. Mitogen-activated protein kinase can be activated by both receptors and shows enhanced early activation in the presence of both ligands. CREB and STAT3 transcription factors are required for synergy and show enhanced DNA-binding activity when both receptors are activated. STAT3 plays a critical role in integration of the signals downstream of the two receptors. When both pathways are activated, STAT3 phosphorylation is sustained for 6 h. This prolonged activation of STAT3 requires deactivation of SHP2 phosphatase. Reduction of SHP2 levels by RNA interference results in greater synergy in neurite outgrowth. Simultaneous knockdown of both SHP2 and STAT3 blocks the synergistic triggering of neurite outgrowth, indicating that STAT3 is downstream of SHP2. CB1R and IL-6R co-stimulation enhanced the differentiation of rat cortical neuron primary cultures. These results provide a mechanism where multiple protein kinases and transcription factors interact to integrate signals from G protein-coupled and cytokine receptor to evoke neurite outgrowth in Neuro2A cells.
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- "Indeed, recent data on the interplay between neurotrophic factors and eCBs highlight a bidirectional regulation through shared second-messenger systems with often opposing outcomes , implying a tightly regulated signalling mechanism relevant to the spatiotemporal position of the cell. In addition, this interaction can be found in a wide variety of tissues from fetal development until adulthood, as well as with other growth factors and growthpromoting interleukins (Zorina et al., 2010), indicating that this molecular interplay is more the rule than the exception. The above is especially the case for pain research, where neurotrophins and eCBs are involved in similar physiological processes but are mostly investigated as singular signalling entities. "
ABSTRACT: Neurotrophins are traditionally known for their roles in neuronal development, function and survival. More recent data has highlighted the importance of neurotrophin signalling in adult signalling contexts, including the regulation of synaptic transmission. In addition, neurotrophin levels are increased in inflammatory and neuropathic pain leading to sensitization to painful stimuli. Endocannabinoid (eCB) signalling was initially studied in the context of synaptic transmission and pain alleviation whilst recently gaining attention due to its involvement in the development of the nervous system. Similar to neurotrophins, eCB levels also rise during pain perception but result in diminished pain sensations. The overlap of cellular functions between neurotrophins and eCB signalling leads to the hypothesis that these signalling systems are positioned to regulate each other and narrow the multitude of actions that both systems can promote to the specific need of the cell. Therefore, in this review, we examine to what extent the involvement of these two signalling systems is co-ordinated as opposed to being coincidental, and causal to neuronal circuit modifications in pain. Available data point to numerous direct molecular interactions between the neurotrophin and eCB signalling systems in developmental and adult contexts, including receptor-level interplay, transcriptional control and synergistic regulation of downstream signalling cascades. Although experimental observations specifically in pain circuits are limited, the universality of downstream signalling systems from both neurotrophin and endocannabinoid receptors suggest an interdependent relationship between these two diverse signalling systems.European Journal of Neuroscience 02/2014; 39(3):334-43. DOI:10.1111/ejn.12431 · 3.18 Impact Factor
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- "The JAK/STAT3 pathway is activated after nerve injury in DRG and motor neurons and maintains neuronal survival and drives axon regeneration [17-23]. Phosphorylation on Tyr705 and transcriptional activation of STAT3 is modulated by cytokines, including IL-1β [2,24,25] and growth factors [26,27]. STAT3 phosphorylation on Ser727 regulates its translocation to the mitochondria and modulates the activity of electron transport Complex I [28-30]. "
ABSTRACT: A luminex-based screen of cytokine expression in dorsal root ganglia (DRG) and nerve of type 1 diabetic rodents revealed interleukin-1 (IL-1alpha) and IL-1beta to be significantly depressed. We, therefore, tested the hypothesis that impaired IL-1alpha and IL-1beta expression in DRG may contribute to aberrant axon regeneration and plasticity seen in diabetic sensory neuropathy. In addition, we determined if these cytokines could optimize mitochondrial bioenergetics since mitochondrial dysfunction is a key etiological factor in diabetic neuropathy. Cytokines IL-1alpha and IL-1beta were reduced 2-fold (p<0.05) in DRG and/or nerve of 2 and 5 month streptozotocin (STZ)-diabetic rats. IL-2 and IL-10 were unchanged. IL-1alpha and IL-1beta induced similar 2 to 3-fold increases in neurite outgrowth in cultures derived from control or diabetic rats (p<0.05). STAT3 phosphorylation on Tyr705 or Ser727 was depressed in DRG from STZ-diabetic mice and treatment of cultures derived from STZ-diabetic rats with IL-1beta for 30 min raised phosphorylation of STAT3 on Tyr705 and Ser727 by 1.5 to 2-fold (p<0.05). shRNA-based or AG490 inhibition of STAT3 activity or shRNA blockade of endogenous IL-1beta expression completely blocked neurite outgrowth. Cultured neurons derived from STZ-diabetic mice were treated for 24 hr with IL-1beta and maximal oxygen consumption rate and spare respiratory capacity, both key measures of bioenergetic fidelity that were depressed in diabetic compared with control neurons, were enhanced 2-fold. This effect was blocked by AG490. Endogenous synthesis of IL-1beta is diminished in nerve tissue in type 1 diabetes and we propose this defect triggers reduced STAT3 signaling and mitochondrial function leading to sup-optimal axonal regeneration and plasticity.Molecular Brain 10/2013; 6(1):45. DOI:10.1186/1756-6606-6-45 · 4.90 Impact Factor
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- "ABHD6 mRNA levels were higher in schizophrenia subjects under 40 years of age (0.043 ± 0.001) and with illness duration of less than 15 years (0.041 ± 0.004) relative to age-matched comparison subjects (0.036 ± 0.002 and 0.036 ± 0.002, respectively) but did not differ in the other groups. disturbances in 2-AG signaling may interfere with neurite formation and dendritic maintenance in schizophrenia (Bellon, 2007; Keimpema et al., 2010; Zorina et al., 2010; Bellon et al., 2011). Furthermore, ABHD6 regulates 2-AG-mediated, CB1R-dependent long term depression of excitatory postsynaptic potentials in adult mouse prefrontal cortex (Marrs et al., 2010), suggesting that alterations in ABHD6 levels may impact glutamatergic signaling in the disorder. "
ABSTRACT: Adolescent cannabis use is associated with greater relative risk, increased symptom severity, and earlier age of onset of schizophrenia. We investigated whether this interaction may be partly attributable to disease-related disturbances in metabolism of the major cortical endocannabinoid 2-arachidonoylglycerol (2-AG). Transcript levels for the recently discovered 2-AG metabolizing enzyme, α-β-hydrolase domain 6 (ABHD6), were assessed using quantitative PCR in the prefrontal cortex of schizophrenia and healthy subjects (n=84) and antipsychotic- or tetrahydrocannabinol-exposed monkeys. ABHD6 mRNA levels were elevated in schizophrenia subjects who were younger and had a shorter illness duration but not in antipsychotic- or tetrahydrocannabinol-exposed monkeys. Higher ABHD6 mRNA levels may increase 2-AG metabolism which may influence susceptibility to cannabis in the earlier stages of schizophrenia.Schizophrenia Research 04/2013; 147(1). DOI:10.1016/j.schres.2013.02.038 · 3.92 Impact Factor