Cannabinoid receptor 1 induces a biphasic ERK activation via multiprotein signaling complex formation of proximal kinases PKCε, Src, and Fyn in primary neurons

Anti-allodynic and medullary modulatory effects of a single dose of delta-9-tetrahydrocannabinol (THC) in neuropathic rats tolerant to morphine

Neuropathic pain (NP) is often treated with opioids, the prolonged use of which causes tolerance to their analgesic effect and can potentially cause death by overdose. The phytocannabinoid delta-9-tetrahydrocannabinol (THC) may be an effective alternative analgesic to treat NP in morphine-tolerant subjects. Male Wistar rats developed NP after spared nerve injury, and were then treated with increasing doses of THC (1, 1.5, 2, 2.5, and 5 mg/kg, intraperitoneally), which reduced mechanical allodynia at the dose of 2.5 and 5 mg/kg. Another group of NP rats were treated with morphine (5 mg/kg, twice daily for 7 days, subcutaneously), until tolerance developed, and on day 8 received a single dose of THC (2.5 mg/kg), which significantly reduced mechanical allodynia. To evaluate the modulation of THC in the descending pain pathway, in vivo electrophysiological recordings of pronociceptive ON cells and antinociceptive OFF cells in the rostroventral medulla (RVM) were recorded after intra-PAG microinjection of THC (10 μg/μl). NP rats with morphine tolerance, compared to the control one, showed a tonic reduction of the spontaneous firing rate of ON cells by 44%, but the THC was able to further decrease it (a hallmark of many analgesic drugs acting at supraspinal level). On the other hand, the firing rate, of the antinociceptive OFF cells was increased after morphine tolerance by 133%, but the THC failed to further activate it. Altogether, these findings indicate that a single dose of THC produces antiallodynic effect in individuals with NP who are tolerant to morphine, acting mostly on the ON cells of the descending pain pathways, but not on OFF cells.

Neuroprotection and Beyond: The Central Role of CB1 and CB2 Receptors in Stroke Recovery

The endocannabinoid system, with its intricate presence in numerous cells, tissues, and organs, offers a compelling avenue for therapeutic interventions. Central to this system are the cannabinoid receptors 1 and 2 (CB1R and CB2R), whose ubiquity can introduce complexities in targeted treatments due to their wide-ranging physiological influence. Injuries to the central nervous system (CNS), including strokes and traumatic brain injuries, induce localized pro-inflammatory immune responses, termed neuroinflammation. Research has shown that compensatory immunodepression usually follows, and these mechanisms might influence immunity, potentially affecting infection risks in patients. As traditional preventive treatments like antibiotics face challenges, the exploration of immunomodulatory therapies offers a promising alternative. This review delves into the potential neuroprotective roles of the cannabinoid receptors: CB1R's involvement in mitigating excitotoxicity and CB2R's dual role in promoting cell survival and anti-inflammatory responses. However, the potential of cannabinoids to reduce neuroinflammation must be weighed against the risk of exacerbating immunodepression. Though the endocannabinoid system promises numerous therapeutic benefits, understanding its multifaceted signaling mechanisms and outcomes remains a challenge.

N-arachidonoyl dopamine inhibits epithelial-mesenchymal transition of breast cancer cells through ERK signaling and decreasing the cellular cholesterol

N-acyl dopamines (NADAs) are bioactive lipids of the endovanilloid family with known cytotoxicity for the cancer cells; however, the available data on the participation of the endovanilloids in epithelial-mesenchymal transition (EMT) and cancer stemness are controversial. This study unveils the inhibitory role of N-arachidonoyl dopamine (AA-DA), a typical representative of the NADA family, in breast cancer cell migration, EMT, and stemness. AA-DA treatment also led to a decrease in cholesterol biosynthesis gene expressions, and addition of exogenous cholesterol reverted these AA-DA-mediated inhibitory effects. Notably, AA-DA treatment inhibited the key regulatory gene of the cholesterol biosynthesis pathway, sterol regulatory element-binding protein 1 (SREBP1), with concurrent repression of the endoplasmic reticulum kinase 1/2 (ERK1/2) pathway. Furthermore, U0126, an ERK inhibitor, inhibited SREBP1 and decreased cellular cholesterol level, unwinding the molecular mechanism behind AA-DA-mediated anticancer activity. Thus, we, for the first time, revealed that AA-DA counteracts breast cancer EMT via inhibition of ERK signaling and cholesterol content.

Cannabinoid Receptors: An Update on Cell Signaling, Pathophysiological Roles and Therapeutic Opportunities in Neurological, Cardiovascular, and Inflammatory Diseases

The identification of the human cannabinoid receptors and their roles in health and disease, has been one of the most significant biochemical and pharmacological advancements to have occurred in the past few decades. In spite of the major strides made in furthering endocannabinoid research, therapeutic exploitation of the endocannabinoid system has often been a challenging task. An impaired endocannabinoid tone often manifests as changes in expression and/or functions of type 1 and/or type 2 cannabinoid receptors. It becomes important to understand how alterations in cannabinoid receptor cellular signaling can lead to disruptions in major physiological and biological functions, as they are often associated with the pathogenesis of several neurological, cardiovascular, metabolic, and inflammatory diseases. This review focusses mostly on the pathophysiological roles of type 1 and type 2 cannabinoid receptors, and it attempts to integrate both cellular and physiological functions of the cannabinoid receptors. Apart from an updated review of pre-clinical and clinical studies, the adequacy/inadequacy of cannabinoid-based therapeutics in various pathological conditions is also highlighted. Finally, alternative strategies to modulate endocannabinoid tone, and future directions are also emphasized.

Neurotropic activity and safety of methylene-cycloalkylacetate (MCA) derivative 3-(3-allyl-2-methylenecyclohexyl) propanoic acid

Polyneuropathy is a disease involving multiple peripheral nerves injuries. Axon regrowth remains the major prerequisite for plasticity, regeneration, circuit formation, and eventually functional recovery and therefore, regulation of neurite outgrowth might be a candidate for treating polyneuropathies. In a recent study, we synthesized and established the methylene-cycloalkylacetate (MCAs) pharmacophore as a lead for the development of a neurotropic drug (inducing neurite/axonal outgrowth) using the PC12 neuronal model. In the present study we extended the characterizations of the in vitro neurotropic effect of the derivative 3-(3-allyl-2-methylenecyclohexyl) propanoic acid (MCA-13) on dorsal root ganglia and spinal cord neuronal cultures and analyzed its safety properties using blood biochemistry and cell counting, acute toxicity evaluation in mice and different in vitro "off-target" pharmacological evaluations. This MCA derivative deserves further preclinical mechanistic pharmacological characterizations including therapeutic efficacy in in vivo animal models of polyneuropathies, toward development of a clinically relevant neurotropic drug.

Protein Interactors and Trafficking Pathways That Regulate the Cannabinoid Type 1 Receptor (CB1R)

The endocannabinoid system (ECS) acts as a negative feedback mechanism to suppress synaptic transmission and plays a major role in a diverse range of brain functions including, for example, the regulation of mood, energy balance, and learning and memory. The function and dysfunction of the ECS are strongly implicated in multiple psychiatric, neurological, and neurodegenerative diseases. Cannabinoid type 1 receptor (CB1R) is the most abundant G protein-coupled receptor (GPCR) expressed in the brain and, as for any synaptic receptor, CB1R needs to be in the right place at the right time to respond appropriately to changing synaptic circumstances. While CB1R is found intracellularly throughout neurons, its surface expression is highly polarized to the axonal membrane, consistent with its functional expression at presynaptic sites. Surprisingly, despite the importance of CB1R, the interacting proteins and molecular mechanisms that regulate the highly polarized distribution and function of CB1R remain relatively poorly understood. Here we set out what is currently known about the trafficking pathways and protein interactions that underpin the surface expression and axonal polarity of CB1R, and highlight key questions that still need to be addressed.

PKCε-dependent H-Ras activation encompasses the recruitment of the RasGEF SOS1 and of the RasGAP neurofibromin in the lipid rafts of embryonic neurons

The spatial organization of plasma membrane proteins is a key factor in the generation of distinct signal outputs, especially for PKC/Ras/ERK signalling. Regulation of activation of the membrane-bound Ras, critical for neuronal differentiation and highly specialized functions, is controlled by exchanges in nucleotides catalyzed by nucleotide exchange factors (GEFs) for GTP loading and Ras activation, and by Ras GTPase Activated Proteins (RasGAPs) that lead to activation of the intrinsic GTPase activity of Ras and thus its inactivation. PKCs are potent Ras activators yet the mechanistic details of these interactions, or the involvement of specific PKC isoforms are now beginning to be addressed. Even less known is the topology where RasGAPs terminate Ras activation. Towards this aim, we isolated lipid rafts from chick embryo neural tissue and primary neuronal cultures when PKCε is the prominent isoform and in combination with in vitro kinase assays, we now show that, in response the PKCε-specific activating peptide ψεRACK, an activated PKCε is recruited to lipid rafts; similar mobility was established when PKCε was physiologically activated with the Cannabinoid receptor 1 (CB1) agonist methanandamide. Activation of H-Ras for both agents was then established for the first time using in vivo RasGAP activity assays, which showed similar temporal profiles of activation and lateral mobility. Moreover, we found that the GEF SOS1, and the major neuronal RasGAP neurofibromin, a specific PKCε substrate, were both transiently significantly enriched in the rafts. Finally, our in silico analysis revealed a highly probable, conserved palmitoylation site adjacent to a CARC motif on neurofibromin, both of which are included only in the RasGAP related domain type I (GRDI) with the known high H-RasGAP activity. Taken together, these results suggest that PKCε activation regulates the spatial plasma membrane enrichments of both SOS1 and neurofibromin, thus controlling the output of activated H-Ras available for downstream signalling in neurons.

miR-23b-3p and miR-130a-5p affect cell growth, migration and invasion by targeting CB1R via the Wnt/β-catenin signaling pathway in gastric carcinoma

Background

Gastric cancer (GC) is the most common malignancy and third leading cause of cancer mortality worldwide. The identification of a sensitive biomarker as well as effective therapeutic targets for the treatment of GC is of critical importance. microRNAs play significant roles in the development of cancer and may serve as promising therapeutic targets.

Methods

The mRNA and protein expression of CB1R were studied both in GC cells and tissues. GC cell lines with specific gene overexpression and knockdown vectors were constructed. CCK-8 assay, matrigel invasion and colony formation assays were performed to evaluate the proliferation and invasion abilities. The binding and regulatory effects of miR-23b-3 and miR-130a-5p on CB1R mRNA were investigated using a luciferase reporter assay. Western blot analysis was performed to explore the potential interaction proteins of CB1R.

Results

In the present study, it was demonstrated that the cannabinoid receptor 1 (CB1R) was overexpressed, and miR-23b-3p and miR-130a-5p were downregulated, in GC cells. In addition, the results revealed that these effects are associated with malignant biological behaviors exhibited by GC cells. Furthermore, miR-23b-3p and miR-130a-5p may regulate CB1R expression via the Wnt/β-catenin signaling pathway.

Conclusion

Our results suggested dysregulation of CB1R expression is closely related to the malignant biological behavior of gastric cancer cells. miRNA/CB1R-based therapy may represent a promising therapeutic strategy for the clinical treatment of GC patients.

Gαs signalling of the CB1 receptor and the influence of receptor number

BACKGROUND AND PURPOSE

CB1 receptor signalling is canonically mediated through inhibitory Gαi proteins, but occurs through other G proteins under some circumstances, Gαs being the most characterized secondary pathway. Determinants of this signalling switch identified to date include Gαi blockade, CB1 /D2 receptor co-stimulation, CB1 agonist class and cell background. Hence, we examined the effects of receptor number and different ligands on CB1 receptor signalling.

EXPERIMENTAL APPROACH

CB1 receptors were expressed in HEK cells at different levels, and signalling characterized for cAMP by real-time BRET biosensor -CAMYEL - and for phospho-ERK by AlphaScreen. Homogenate and whole cell radioligand binding assays were performed to characterize AM6544, a novel irreversible CB1 receptor antagonist.

KEY RESULTS

In HEK cells expressing high levels of CB1 receptors, agonist treatment stimulated cAMP, a response not known to be mediated by receptor number. Δ9 -THC and BAY59-3074 increased cAMP only in high-expressing cells pretreated with pertussis toxin, and agonists demonstrated more diverse signalling profiles in the stimulatory pathway than the canonical inhibitory pathway. Pharmacological CB1 receptor knockdown and Gαi 1 supplementation restored canonical Gαi signalling to high-expressing cells. Constitutive signalling in both low- and high-expressing cells was Gαi -mediated.

CONCLUSION AND IMPLICATIONS

CB1 receptor coupling to opposing G proteins is determined by both receptor and G protein expression levels, which underpins a mechanism for non-canonical signalling in a fashion consistent with Gαs signalling. CB1 receptors mediate opposite consequences in endpoints such as tumour viability depending on expression levels; our results may help to explain such effects at the level of G protein coupling.

Analysis of natural product regulation of cannabinoid receptors in the treatment of human disease

The organized, tightly regulated signaling relays engaged by the cannabinoid receptors (CBs) and their ligands, G proteins and other effectors, together constitute the endocannabinoid system (ECS). This system governs many biological functions including cell proliferation, regulation of ion transport and neuronal messaging. This review will firstly examine the physiology of the ECS, briefly discussing some anomalies in the relay of the ECS signaling as these are consequently linked to maladies of global concern including neurological disorders, cardiovascular disease and cancer. While endogenous ligands are crucial for dispatching messages through the ECS, there are also commonalities in binding affinities with copious exogenous ligands, both natural and synthetic. Therefore, this review provides a comparative analysis of both types of exogenous ligands with emphasis on natural products given their putative safer efficacy and the role of Δ9-tetrahydrocannabinol (Δ9-THC) in uncovering the ECS. Efficacy is congruent to both types of compounds but noteworthy is the effect of a combination therapy to achieve efficacy without unideal side-effects. An example is Sativex that displayed promise in treating Huntington's disease (HD) in preclinical models allowing for its transition to current clinical investigation. Despite the in vitro and preclinical efficacy of Δ9-THC to treat neurodegenerative ailments, its psychotropic effects limit its clinical applicability to treating feeding disorders. We therefore propose further investigation of other compounds and their combinations such as the triterpene, α,β-amyrin that exhibited greater binding affinity to CB₁ than CB₂ and was more potent than Δ9-THC and the N-alkylamides that exhibited CB₂ selective affinity; the latter can be explored towards peripherally exclusive ECS modulation. The synthetic CB₁ antagonist, Rimonabant was pulled from commercial markets for the treatment of diabetes, however its analogue SR144528 maybe an ideal lead molecule towards this end and HU-210 and Org27569 are also promising synthetic small molecules.

Cannabinoid CB1 and CB2 receptors differentially modulate L- and T-type Ca2+ channels in rat retinal ganglion cells

Endocannabinoid signaling system is involved in regulating multiple neuronal functions in the central nervous system by activating G-protein coupled cannabinoid CB1 and CB2 receptors (CB1Rs and CB2Rs). Growing evidence has shown that CB1Rs and CB2Rs are extensively expressed in retinal ganglion cells (RGCs). Here, modulation of L- and T-types Ca²⁺ channels by activating CB1Rs and CB2Rs in RGCs was investigated. Triple immunofluorescent staining showed that L-type subunit Ca_V1.2 was co-localized with T-type subunits (Ca_V3.1, Ca_V3.2 and Ca_V3.3) in rat RGCs. In acutely isolated rat RGCs, the CB1R agonist WIN55212-2 suppressed both peak and steady-state Ca²⁺ currents in a dose-dependent manner, with IC₅₀ being 9.6 μM and 8.4 μM, respectively. It was further shown that activation of CB1Rs by WIN55212-2 or ACEA, another CB1R agonist, significantly suppressed both L- and T-type Ca²⁺ currents, and shifted inactivation curve of T-type one toward hyperpolarization direction. While the effect on L-type Ca²⁺ channels was mediated by intracellular cAMP/protein kinase A (PKA), mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) and calcium/calmodulin-dependent protein kinase II (CaMKII) signaling pathways, only CaMKII signaling pathway was involved in the effect on T-type Ca²⁺ channels. Furthermore, CB65 and HU308, two specific CB2R agonists, significantly suppressed T-type Ca²⁺ channels, which was mediated by intracellular cAMP/PKA and CaMKII signaling pathways, but had no effect on L-type channels. These results imply that endogenous cannabinoids may modulate the excitability and the output of RGCs by differentially suppressing the activity of L- and T-type Ca²⁺ channels through activation of CB1Rs and CB2Rs. This article is part of the Special Issue entitled "A New Dawn in Cannabinoid Neurobiology".

Cannabinoid Receptor Interacting Protein 1a Competition with β-Arrestin for CB1 Receptor Binding Sites

Cannabinoid receptor interacting protein 1a (CRIP1a) is a CB₁ receptor (CB₁R) distal C-terminal-associated protein that alters CB₁R interactions with G-proteins. We tested the hypothesis that CRIP1a is capable of also altering CB₁R interactions with β-arrestin proteins that interact with the CB₁R at the C-terminus. Coimmunoprecipitation studies indicated that CB₁R associates in complexes with either CRIP1a or β-arrestin, but CRIP1a and β-arrestin fail to coimmunoprecipitate with each other. This suggests a competition for CRIP1a and β-arrestin binding to the CB₁R, which we hypothesized could attenuate the action of β-arrestin to mediate CB₁R internalization. We determined that agonist-mediated reduction of the density of cell surface endogenously expressed CB₁Rs was clathrin and dynamin dependent and could be modeled as agonist-induced aggregation of transiently expressed GFP-CB₁R. CRIP1a overexpression attenuated CP55940-mediated GFP-CB₁R as well as endogenous β-arrestin redistribution to punctae, and conversely, CRIP1a knockdown augmented β-arrestin redistribution to punctae. Peptides mimicking the CB₁R C-terminus could bind to both CRIP1a in cell extracts as well as purified recombinant CRIP1a. Affinity pull-down studies revealed that phosphorylation at threonine-468 of a CB₁R distal C-terminus 14-mer peptide reduced CB₁R-CRIP1a association. Coimmunoprecipitation of CB₁R protein complexes demonstrated that central or distal C-terminal peptides competed for the CB₁R association with CRIP1a, but that a phosphorylated central C-terminal peptide competed for association with β-arrestin 1, and phosphorylated central or distal C-terminal peptides competed for association with β-arrestin 2. Thus, CRIP1a can compete with β-arrestins for interaction with C-terminal CB₁R domains that could affect agonist-driven, β-arrestin-mediated internalization of the CB₁R.

Modulation of cellular redox homeostasis by the endocannabinoid system

The endocannabinoid system (ECS) and reactive oxygen species (ROS) constitute two key cellular signalling systems that participate in the modulation of diverse cellular functions. Importantly, growing evidence suggests that cross-talk between these two prominent signalling systems acts to modulate functionality of the ECS as well as redox homeostasis in different cell types. Herein, we review and discuss evidence pertaining to ECS-induced regulation of ROS generating and scavenging mechanisms, as well as highlighting emerging work that supports redox modulation of ECS function. Functionally, the studies outlined reveal that interactions between the ECS and ROS signalling systems can be both stimulatory and inhibitory in nature, depending on cell stimulus, the source of ROS species and cell context. Importantly, such cross-talk may act to maintain cell function, whereas abnormalities in either system may propagate and undermine the stability of both systems, thereby contributing to various pathologies associated with their dysregulation.

Fyn is an intermediate kinase that BDNF utilizes to promote oligodendrocyte myelination

Fyn, a member of the Src family of nonreceptor tyrosine kinases, promotes central nervous system myelination during development; however the mechanisms mediating this effect remain unknown. Here we show that Fyn phosphorylation is modulated by BDNF in vivo. Concordant with this, we find that BDNF stimulates Fyn phosphorylation in myelinating cocultures, an effect dependent on oligodendroglial expression of TrkB. Importantly, PP2, a pharmacological inhibitor of Src family kinases, not only abrogated the promyelinating influence of BDNF in vitro, but also attenuated BDNF-induced phosphorylation of Erk1/2 in oligodendrocytes. Over-expression of Fyn in oligodendrocytes significantly promotes phosphorylation of Erk1/2, and promotes myelination to the extent that exogenous BDNF exerts no additive effect in vitro. In contrast, expression of a kinase-dead mutant of Fyn in oligodendrocytes significantly inhibited BDNF-induced activation of Erk1/2 and abrogated the promyelinating effect of BDNF. Analysis of white matter tracts in vivo revealed that phosphorylated Fyn primarily colocalized with mature oligodendrocytes, and was rarely observed in oligodendrocyte progenitor cells, a profile that closely parallels the detection of phosphorylated Erk1/2 in the developing central nervous system. Taken together, these data identify that Fyn kinase exerts a key role in mediating the promyelinating influence of BDNF. Here we identify a pathway in which BDNF activation of oligodendroglial TrkB receptors stimulates the phosphorylation of Fyn, a necessary step required to potentiate the phosphorylation of Erk1/2, which in turn regulates oligodendrocyte myelination.

Detection and Differentiation of Threonine- and Tyrosine-Monophosphorylated Forms of ERK1/2 by Capillary Isoelectric Focusing-Immunoassay

The extracellular signal regulated kinases ERK1/2 play important roles in the regulation of diverse cellular functions and have been implicated in several human diseases. In addition to the fully activated, diphosphorylated ERK1/2 protein, monophosphorylated forms of ERK1/2 have been observed, which may have distinct biological functions. We report here on the highly sensitive detection and differentiation of unphosphorylated, threonine-phosphorylated (pT), tyrosine-phosphorylated (pY) and diphosphorylated ERK1 and ERK2 by capillary isoelectric focusing followed by immunological detection (CIEF-immunoassay). Eight different phosphorylated and unphosphorylated forms of ERK1/2 were resolved according to charge. The unequivocal identification and differentiation of ERK1 and ERK2 forms monophosphorylated at either threonine or tyrosine was achieved by competitive blocking with specific phospho-peptides and different phosphorylation-sensitive antibodies. The suitability of the additional pT-ERK1/2 and pY-ERK1/2 differentiation for the time-resolved in-depth study of phospho-form distribution in response to specific stimuli is demonstrated in human neuroblastoma SH-SY5Y and monocytic THP-1 cell lines, and in human peripheral blood mononuclear cells.

Long-term changes in the ghrelin-CB1R axis associated with the maintenance of lower body weight after sleeve gastrectomy

OBJECTIVES

In the hypothalamus, the molecular actions of receptors for growth hormone secretagogue (ghrelin) receptor-GHSR, leptin receptor-b (LEPRb), Melanocortin-4 receptor (MC4R) and Cannabinoid-1 receptor (CB1R) regulate energy homeostasis and body weight. We hypothesized that the acute loss of stomach tissue upon sleeve gastrectomy (SG), performed to treat obesity, imposes modulations on the expression of these receptors in the brain to sustain weight loss.

METHODS

Rats, induced to obesity with high-fat diet were randomized to SG- or sham-operation groups and killed at 30 or 90 days post surgery, when the expression of Ghrl, Mboat4 and Cnr1 in the stomach, and Ghsr, Leprb, Mc4r and Cnr1 in distinct brain areas was assessed by reverse transcription-PCR and western blotting.

RESULTS

SG acutely reduced body weight and fat mass and suppressed the remnant stomach mRNA levels of preproghrelin and ghrelin O-acyltransferase, which correlated well with long-term decreases in CB1R mRNA. In the hypothalamus, increases in GHSR and decreases in CB1R and LEPRb by 30 days were followed by further downregulation of CB1R and an increase in MC4R by 90 days.

CONCLUSIONS

Post SG, acyl-ghrelin initiates a temporal hierarchy of molecular events in the gut-brain axis that may both explain the sustained lower body weight and suggest intervention into the cannabinoid pathways for additional therapeutic benefits.

PKCε signalling activates ERK1/2, and regulates aggrecan, ADAMTS5, and miR377 gene expression in human nucleus pulposus cells

The protein kinase C (PKC) signaling, a major regulator of chondrocytic differentiation, has been also implicated in pathological extracellular matrix remodeling, and here we investigate the mechanism of PKCε-dependent regulation of the chondrocytic phenotype in human nucleus pulposus (NP) cells derived from herniated disks. NP cells from each donor were successfully propagated for 25+ culture passages, with remarkable tolerance to repeated freeze-and-thaw cycles throughout long-term culturing. More specifically, after an initial downregulation of COL2A1, a stable chondrocytic phenotype was attested by the levels of mRNA expression for aggrecan, biglycan, fibromodulin, and lumican, while higher expression of SOX-trio and Patched-1 witnessed further differentiation potential. NP cells in culture also exhibited a stable molecular profile of PKC isoforms: throughout patient samples and passages, mRNAs for PKC α, δ, ε, ζ, η, ι, and µ were steadily detected, whereas β, γ, and θ were not. Focusing on the signalling of PKCε, an isoform that may confer protection against degeneration, we found that activation with the PKCε-specific activator small peptide ψεRACK led sequentially to a prolonged activation of ERK1/2, increased abundance of the early gene products ATF, CREB1, and Fos with concurrent silencing of transcription for Ki67, and increases in mRNA expression for aggrecan. More importantly, ψεRACK induced upregulation of hsa-miR-377 expression, coupled to decreases in ADAMTS5 and cleaved aggrecan. Therefore, PKCε activation in late passage NP cells may represent a molecular basis for aggrecan availability, as part of an PKCε/ERK/CREB/AP-1-dependent transcriptional program that includes upregulation of both chondrogenic genes and microRNAs. Moreover, this pathway should be considered as a target for understanding the molecular mechanism of IVD degeneration and for therapeutic restoration of degenerated disks.

PKC-epsilon activation is required for recognition memory in the rat

Activation of PKCɛ, an abundant and developmentally regulated PKC isoform in the brain, has been implicated in memory throughout life and across species. Yet, direct evidence for a mechanistic role for PKCɛ in memory is still lacking. Hence, we sought to evaluate this in rats, using short-term treatments with two PKCɛ-selective peptides, the inhibitory ɛV1-2 and the activating ψɛRACK, and the novel object recognition task (NORT). Our results show that the PKCɛ-selective activator ψɛRACK, did not have a significant effect on recognition memory. In the short time frames used, however, inhibition of PKCɛ activation with the peptide inhibitor ɛV1-2 significantly impaired recognition memory. Moreover, when we addressed at the molecular level the immediate proximal signalling events of PKCɛ activation in acutely dissected rat hippocampi, we found that ψɛRACK increased in a time-dependent manner phosphorylation of MARCKS and activation of Src, Raf, and finally ERK1/2, whereas ɛV1-2 inhibited all basal activity of this pathway. Taken together, these findings present the first direct evidence that PKCɛ activation is an essential molecular component of recognition memory and point toward the use of systemically administered PKCɛ-regulating peptides as memory study tools and putative therapeutic agents.

The endocannabinoid signaling system in cancer

Changes in lipid metabolism are intimately related to cancer. Several classes of bioactive lipids play roles in the regulation of signaling pathways involved in neoplastic transformation and tumor growth and progression. The endocannabinoid system, comprising lipid-derived endocannabinoids, their G-protein-coupled receptors (GPCRs), and the enzymes for their metabolism, is emerging as a promising therapeutic target in cancer. This report highlights the main signaling pathways for the antitumor effects of the endocannabinoid system in cancer and its basic role in cancer pathogenesis, and discusses the alternative view of cannabinoid receptors as tumor promoters. We focus on new players in the antitumor action of the endocannabinoid system and on emerging crosstalk among cannabinoid receptors and other membrane or nuclear receptors involved in cancer. We also discuss the enzyme MAGL, a key player in endocannabinoid metabolism that was recently recognized as a marker of tumor lipogenic phenotype.

B-Raf and CRHR1 internalization mediate biphasic ERK1/2 activation by CRH in hippocampal HT22 Cells

CRH is a key regulator of neuroendocrine, autonomic, and behavioral response to stress. CRH-stimulated CRH receptor 1 (CRHR1) activates ERK1/2 depending on intracellular context. In a previous work, we demonstrated that CRH activates ERK1/2 in limbic areas of the mouse brain (hippocampus and basolateral amygdala). ERK1/2 is an essential mediator of hippocampal physiological processes including emotional behavior, synaptic plasticity, learning, and memory. To elucidate the molecular mechanisms by which CRH activates ERK1/2 in hippocampal neurons, we used the mouse hippocampal cell line HT22. We document for the first time that ERK1/2 activation in response to CRH is biphasic, involving a first cAMP- and B-Raf-dependent early phase and a second phase that critically depends on CRHR1 internalization and β-arrestin2. By means of mass-spectrometry-based screening, we identified B-Raf-associated proteins that coimmunoprecipitate with endogenous B-Raf after CRHR1 activation. Using molecular and pharmacological tools, the functional impact of selected B-Raf partners in CRH-dependent ERK1/2 activation was dissected. These results indicate that 14-3-3 proteins, protein kinase A, and Rap1, are essential for early CRH-induced ERK1/2 activation, whereas dynamin and vimentin are required for the CRHR1 internalization-dependent phase. Both phases of ERK1/2 activation depend on calcium influx and are affected by calcium/calmodulin-dependent protein kinase II inactivation. Thus, this report describes the dynamics and biphasic nature of ERK1/2 activation downstream neuronal CRHR1 and identifies several new critical components of the CRHR1 signaling machinery that selectively controls the early and late phases of ERK1/2 activation, thus providing new potential therapeutic targets for stress-related disorders.

Molecular model of cannabis sensitivity in developing neuronal circuits

Prenatal cannabis exposure can complicate in utero development of the nervous system. Cannabis impacts the formation and functions of neuronal circuitries by targeting cannabinoid receptors. Endocannabinoid signaling emerges as a signaling cassette that orchestrates neuronal differentiation programs through the precisely timed interaction of endocannabinoid ligands with their cognate cannabinoid receptors. By indiscriminately prolonging the 'switched-on' period of cannabinoid receptors, cannabis can hijack endocannabinoid signals to evoke molecular rearrangements, leading to the erroneous wiring of neuronal networks. Here, we formulate a hierarchical network design necessary and sufficient to describe the molecular underpinnings of cannabis-induced neural growth defects. We integrate signalosome components, deduced from genome- and proteome-wide arrays and candidate analyses, to propose a mechanistic hypothesis of how cannabis-induced ectopic cannabinoid receptor activity overrides physiological neurodevelopmental endocannabinoid signals, affecting the timely formation of synapses.