Endocannabinoids, particularly 2-arachidonoyl glycerol (2-AG), impact the directional turning and motility of a developing axon by activating CB 1 cannabinoid receptors (CB 1 Rs) in its growth cone. Recent findings posit that sn-1-diacylglycerol lipases (DAGL␣/␤) synthesize 2-AG in the motile axon segment of developing pyramidal cells. Coincident axonal targeting of CB 1 Rs and DAGLs prompts the hypothesis that autocrine 2-AG signaling facilitates axonal outgrowth. However, DAGLs alone are insufficient to account for the spatial specificity and dynamics of 2-AG signaling. Therefore, we hypothesized that local 2-AG degradation by monoacylglycerol lipase (MGL) must play a role. We determined how subcellular recruitment of MGL is temporally and spatially restricted to establish the signaling competence of 2-AG during axonal growth. MGL is expressed in central and peripheral axons of the fetal nervous system by embryonic day 12.5. MGL coexists with DAGL␣ and CB 1 Rs in corticofugal axons of pyramidal cells. Here, MGL and DAGL␣ undergo differential axonal targeting with MGL being excluded from the motile neurite tip. Thus, spatially confined MGL activity generates a 2-AG-sensing microdomain and configures 2-AG signaling to promote axonal growth. Once synaptogenesis commences, MGL disperses in stationary growth cones. The axonal polarity of MGL is maintained by differential proteasomal degradation because inhibiting the ubiquitin proteasome system also induces axonal MGL redistribution. Because MGL inactivation drives a CB 1 R-dependent axonal growth response, we conclude that 2-AG may act as a focal protrusive signal for developing neurons and whose regulated metabolism is critical for attaining correct axonal complexity.

Children exposed in utero to cannabis present permanent neurobehavioral and cognitive impairments. Psychoactive constituents from Cannabis spp., particularly D 9-tetrahydrocannabinol (THC), bind to cannabinoid receptors in the fetal brain. However, it is unknown whether THC can trigger a cannabinoid receptordriven molecular cascade to disrupt neuronal specification. Here, we show that repeated THC exposure disrupts endocannabinoid signaling, particularly the temporal dynamics of CB 1 cannabinoid receptor, to rewire the fetal cortical circuitry. By interrogating the THC-sensitive neuronal proteome we identify Superior Cervical Ganglion 10 (SCG10)/stathmin-2, a microtubule-binding protein in axons, as a substrate of altered neuronal connectivity. We find SCG10 mRNA and protein reduced in the hippocampus of midgestational human cannabis-exposed fetuses, defining SCG10 as the first cannabis-driven molecular effector in the developing cerebrum. CB 1 cannabinoid receptor activation recruits c-Jun N-terminal kinases to phosphorylate SCG10, promoting its rapid degradation in situ in motile axons and microtubule stabilization. Thus, THC enables ectopic formation of filopodia and alters axon morphology. These data highlight the maintenance of cytoskeletal dynamics as a molecular target for cannabis, whose imbalance can limit the computational power of neuronal circuitries in affected offspring.

The Ca 2؉ -binding proteins (CBPs) parvalbumin, calbindin, and calretinin are phenotypic markers of terminally differentiated neurons in the adult brain. Although subtle phylogenetic variations in the neuronal distribution of these CBPs may occur, morphologically and functionally diverse subclasses of interneurons harbor these proteins in olfactory and corticolimbic areas. Secretagogin (scgn) is a recently cloned CBP from pancreatic ␤ and neuroendocrine cells. We hypothesized that scgn is expressed in the mammalian brain. We find that scgn is a marker of neuroblasts commuting in the rostral migratory stream. Terminally differentiated neurons in the olfactory bulb retain scgn expression, with scgn being present in periglomerular cells and granular layer interneurons. In the corticolimbic system, scgn identifies granule cells distributed along the dentate gyrus, indusium griseum, and anterior hippocampal continuation emphasizing the shared developmental origins, and cytoarchitectural and functional similarities of these neurons. We also uncover unexpected phylogenetic differences in scgn expression, since this CBP is restricted to primate cholinergic basal forebrain neurons. Overall, we characterize scgn as a neuronspecific CBP whose distribution identifies neuronal subtypes and hierarchical organizing principles in the mammalian brain.cortex ͉ development ͉ interneuron ͉ neurogenesis ͉ stem cell T he ability to release neurotransmitters at chemical synapses, to integrate the activity of diverse synaptic inputs and trigger molecular mechanisms underlying neuronal adaptation, as well as to maintain excitability in neurons rely on the refined spatial and temporal control of momentary changes in cytosolic [Ca 2ϩ ] (1, 2). Ca 2ϩ -binding proteins (CBPs) represent a means to effectively regulate intracellular Ca 2ϩ dynamics (3). Members of the EF-hand family of CBPs invariably contain a 3-D motif to bind Ca 2ϩ at its physiological cytosolic concentrations (4). Some ancestral representatives of this protein family, such as calmodulin, are ubiquitously expressed with a high degree of evolutionary conservation and are involved in the control of fundamental cellular functions ranging from the cell cycle, cell motility and axon polarization to synaptic signaling (3). In contrast, the parvalbumin (PV) and calbindin subfamilies of CBPs, the latter including the vitamin D-dependent 28 kDa isoform of calbindin (CB) and calretinin (CR), exhibit restricted tissue-specific expression patterns in vertebrates (5, 6). During the past decades, PV, CB, and CR received significant attention because of their exquisite developmentally regulated cell type-specific expression in the mammalian nervous system (6-8).CBPs show a unique association with newly generated neurons in the adult brain (9, 10). Neural progenitors that are born in the subependymal zone and migrate in the rostral migratory stream (RMS) to differentiate into interneurons in the olfactory bulb (OB) commonly express CR at their neuroblast stage with select subpopulations ...

Lipid metabolism is critical to coordinate organ development and physiology in response to tissue-autonomous signals and environmental cues. Changes to the availability and signaling of lipid mediators can limit competitiveness, adaptation to environmental stressors, and augment pathological processes. Two classes of lipids, the N-acyl amides and the 2-acyl glycerols, have emerged as important signaling molecules in a wide range of species with important signaling properties, though most of what is known about their cellular functions is from mammalian models. Therefore, expanding available knowledge on the repertoire of these lipids in invertebrates will provide additional avenues of research aimed at elucidating biosynthetic, metabolic, and signaling properties of these molecules. Drosophila melanogaster is a commonly used organism to study intercellular communication, including the functions of bioactive lipids. However, limited information is available on the molecular identity of lipids with putative biological activities in Drosophila. Here, we used a targeted lipidomics approach to identify putative signaling lipids in third instar Drosophila larvae, possessing particularly large lipid mass in their fat body. We identified 2-linoleoyl glycerol, 2-oleoyl glycerol, and 45 N-acyl amides in larval tissues, and validated our findings by the comparative analysis of Oregon-RS, Canton-S and w1118 strains. Data here suggest that Drosophila represent another model system to use for the study of 2-acyl glycerol and N-acyl amide signaling.

Ca-sensor proteins are generally implicated in insulin release through SNARE interactions. Here, secretagogin, whose expression in human pancreatic islets correlates with their insulin content and the incidence of type 2 diabetes, is shown to orchestrate an unexpectedly distinct mechanism. Single-cell RNA-seq reveals retained expression of the TRP family members in β-cells from diabetic donors. Amongst these, pharmacological probing identifies Ca-permeable transient receptor potential vanilloid type 1 channels (TRPV1) as potent inducers of secretagogin expression through recruitment of Sp1 transcription factors. Accordingly, agonist stimulation of TRPV1s fails to rescue insulin release from pancreatic islets of glucose intolerant secretagogin knock-out() mice. However, instead of merely impinging on the SNARE machinery, reduced insulin availability in secretagogin mice is due to β-cell loss, which is underpinned by the collapse of protein folding and deregulation of secretagogin-dependent USP9X deubiquitinase activity. Therefore, and considering the desensitization of TRPV1s in diabetic pancreata, a TRPV1-to-secretagogin regulatory axis seems critical to maintain the structural integrity and signal competence of β-cells.