Background Some chemokine receptors referred to as atypical chemokine receptors (ACKRs) are thought to non-signaling decoys because of their inability to activate typical G-protein signaling pathways. CXCR7, also known as ACKR3, binds to only two chemokines, SDF-1α and I-TAC, and recruits β-arrestins. SDF-1α also binds to its own conventional receptor, CXCR4, involving in homeostatic modulation such as development and immune surveillance as well as pathological conditions such as inflammation, ischemia, and cancers. Recently, CXCR7 is suggested as a key therapeutic target together with CXCR4 in such conditions. However, the molecular mechanisms underlying cellular responses and functional relation with CXCR7 and CXCR4 have not been elucidated, despite massive studies. Therefore, we aimed to reveal the molecular networks of CXCR7 and CXCR4 and compare their effects on cell migration. Methods Base on structural complementation assay using NanoBiT technology, we characterized the distinct mechanisms underlying β-arrestin2 recruitment by both CXCR4 and CXCR7. Crosslinking and immunoprecipitation were conducted to analyze complex formation of the receptors. Gene deletion using CRISPR and reconstitution of the receptors were applied to analysis of ligand-dependent ERK phosphorylation and cell migration. All experiments were performed in triplicate and repeated more than three times. Unpaired Student’s t-tests or ANOVA using PRISM5 software were employed for statistical analyses. Results Ligand binding to CXCR7 does not result in activation of typical signaling pathways via Gα subunits but activation of GRK2 via βγ subunits and receptor phosphorylation with subsequent β-arrestin2 recruitment. In contrast, CXCR4 induced Gαi activation and recruited β-arrestin2 through C-terminal phosphorylation by both GRK2 and GRK5. SDF-1α-stimulated ERK phosphorylation was facilitated by CXCR4, but not CXCR7. Heterodimerization of CXCR4 and CXCR7 was not confirmed in this study, while homodimerization of them was verified by crosslinking experiment and NanoBiT assay. Regarding chemotaxis, SDF-1α-stimulated cell migration was mediated by both CXCR4 and CXCR7. Conclusion This study demonstrates that SDF-1α-stimulated CXCR7 mediates β-arrestin2 recruitment via different molecular networking from that of CXCR4. CXCR7 may be neither a simple scavenger nor auxiliary receptor but plays an essential role in cell migration through cooperation with CXCR4.

Despite the established comorbidity between mood disorders and abnormal eating behaviors, the underlying molecular mechanism and therapeutics remain to be resolved. Here, we show that a spexin-based galanin receptor type 2 agonist (SG2A) simultaneously normalized mood behaviors and body weight in corticosterone pellet-implanted (CORTI) mice, which are underweight and exhibit signs of anhedonia, increased anxiety, and depression. Administration of SG2A into the lateral ventricle produced antidepressive and anxiolytic effects in CORTI mice. Additionally, SG2A led to a recovery of body weight in CORTI mice while it induced significant weight loss in normal mice. In Pavlovian fear-conditioned mice, SG2A decreased contextual and auditory fear memory consolidation but accelerated the extinction of acquired fear memory without altering innate fear and recognition memory. The main action sites of SG2A in the brain may include serotonergic neurons in the dorsal raphe nucleus for mood control, and proopiomelanocortin/corticotropin-releasing hormone neurons in the hypothalamus for appetite and body weight control. Furthermore, intranasal administration of SG2A exerted the same anxiolytic and antidepressant-like effects and decreased food intake and body weight in a dose-dependent manner. Altogether, these results indicate that SG2A holds promise as a clinical treatment for patients with comorbid mood disorders and abnormal appetite/body weight.

FAM19A5 is a secretory protein that is predominantly expressed in the brain. Although the FAM19A5 gene has been found to be associated with neurological and/or psychiatric diseases, only limited information is available on its function in the brain. Using FAM19A5-LacZ knock-in mice, we determined the expression pattern of FAM19A5 in developing and adult brains and identified cell types that express FAM19A5 in naïve and traumatic brain injury (TBI)–induced brains. According to X-gal staining results, FAM19A5 is expressed in the ventricular zone and ganglionic eminence at a very early stage of brain development, suggesting its functions are related to the generation of neural stem cells and oligodendrocyte precursor cells (OPCs). In the later stages of developing embryos and in adult mice, FAM19A5 expression expanded broadly to particular regions of the brain, including layers 2/3 and 5 of the cortex, cornu amonis (CA) region of the hippocampus, and the corpus callosum. X-gal staining combined with immunostaining for a variety of cell-type markers revealed that FAM19A5 is expressed in many different cell types, including neurons, OPCs, astrocytes, and microglia; however, only some populations of these cell types produce FAM19A5. In a subpopulation of neuronal cells, TBI led to increased X-gal staining that extended to the nucleus, marked by slightly condensed content and increased heterochromatin formation along the nuclear border. Similarly, nuclear extension of X-gal staining occurred in a subpopulation of OPCs in the corpus callosum of the TBI-induced brain. Together, these results suggest that FAM19A5 plays a role in nervous system development from an early stage and increases its expression in response to pathological conditions in subsets of neurons and OPCs of the adult brain.

Neurodevelopment and mature brain function are spatiotemporally regulated by various cytokines and chemokines. The chemokine-like neuropeptide FAM19A1 is a member of family with sequence similarity 19 (FAM19), which is predominantly expressed in the brain. Its highly conserved amino acid sequence among vertebrates suggests that FAM19A1 may play important physiological roles in neurodevelopment and brain function. Here we used a LacZ reporter gene system to map the expression pattern of the FAM19A1 gene in the mouse brain. The FAM19A1 expression was observed in several brain regions starting during embryonic brain development. As the brain matured, the FAM19A1 expression was detected in the pyramidal cells of cortical layers 2/3 and 5 and in several limbic areas, including the hippocampus and the amygdala. FAM19A1-deficient mice were used to evaluate the physiological contribution of FAM19A1 to various brain functions. In behavior analysis, FAM19A1deficient mice exhibited several abnormal behaviors, including hyperactive locomotor behavior, longterm memory deficits and fear acquisition failure. These findings provide insight into the potential contributions of FAM19A1 to neurodevelopment and mature brain function. Developmental and physiological processes in the central nervous system (CNS) are tightly regulated by a series of orchestrated gene expressions to promote the formation of dynamic neural circuitries and to execute diverse brain functions 1,2. These gene expressions are heavily influenced by numerous extrinsic factors, including secretory signaling molecules, extracellular matrix proteins, and membrane-bound signaling proteins. In particular, several types of secretory proteins are produced by brain cells and play crucial roles in biological processes in the CNS, including neurogenesis and synaptic plasticity 3-5. Cytokines and chemokines are secretory proteins that mediate a diverse range of functions in the CNS 6. In neural induction process, cytokines are known to act as regulators in the self-renewal of neural stem cells (NSCs) and progenitor differentiation 7,8. Moreover, chemokines, a subclass of cytokines, are involved in neural development. For instance, C-X-C motif chemokine 12 (CXCL12) regulates neural migration and axon pathfinding via the C-X-C chemokine receptor type 4 (CXCR4) signaling pathway 9,10. Furthermore, in the adult nervous system, cytokines such as leukemia inhibitory factor (LIF) control neurotransmitter and neuropeptide profiles 11,12 , whereas interleukin-1 beta (IL-1β) modulates the activity of local neural networks via reconstructing synaptic plasticity and intercellular communication 13,14. Taken together, these findings indicate that the normal development and physiological functions within the CNS depend on the spatiotemporal regulation of several cytokines and chemokines. Given emerging evidence that abnormal cytokine profiles are associated with neurodevelopmental disorders such as autism spectrum disorder (ASD) and attention deficit hyperactive disorder (ADHD), it is im...

Breast cancer exhibits high lethality in women because it is frequently detected at an advanced stage and aggressive forms such as triple-negative breast cancer (TNBC), which are often characterized by metastasis through colonization of secondary tumors. Thus, developing therapeutic agents that target the metastatic process is crucial to successfully treat aggressive breast cancer. We evaluated SP-8356, an anti-inflammatory synthetic verbenone derivative, with respect to its regulation of breast cancer cell behavior and cancer progression. Treatment of SP-8356 arrested cell cycle and reduced growth in various types of breast cancer cells with mild cytotoxicity. Particularly, SP-8356 significantly reduced the motility and invasiveness of TNBC cells. Assays using an in vivo xenograft mouse model confirmed the cell-specific anti-proliferative and anti-metastatic activity of SP-8356. Functional studies revealed that SP-8356 suppressed serum response element-dependent reporter gene expression and NF-κB-related signaling, resulting in downregulation of many genes related to cancer invasion. We conclude that SP-8356 suppresses breast cancer progression through multimodal functions, including inhibition of NF-κB signaling and growth-related signaling pathways.