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Summary: Malignant peripheral nerve sheath tumors (MPNSTs) are soft tissue sarcomas that arise in connective tissue surrounding peripheral nerves. They occur sporadically in a subset of patients with neurofibromatosis type 1 (NF1). MPNSTs are highly aggressive, therapeutically resistant, and typically fatal. Using comparative transcriptome analysis, we identified CXCR4, a G-protein-coupled receptor, as highly expressed in mouse models of NF1-deficient MPNSTs, but not in nontransformed precursor cells. The chemokine receptor CXCR4 and its ligand, CXCL12, promote MPNST growth by stimulating cyclin D1 expression and cell-cycle progression through PI3-kinase (PI3K) and β-catenin signaling. Suppression of CXCR4 activity either by shRNA or pharmacological inhibition decreases MPNST cell growth in culture and inhibits tumorigenesis in allografts and in spontaneous genetic mouse models of MPNST. We further demonstrate conservation of these activated molecular pathways in human MPNSTs. Our findings indicate a role for CXCR4 in NF1-associated MPNST development and identify a therapeutic target. [Copyright &y& Elsevier]

Summary: Signal transducers and activators of transcription 1 (STAT1) is activated by tyrosine phosphorylation upon interferon-γ (IFN-γ) stimulation. Phosphorylated STAT1 translocates into nucleus to initiate the transcription of IFN-γ target genes that are important in mediating antiviral, antiproliferative, and immune response. The inactivation of STAT1 is mainly accomplished via tyrosine dephosphorylation by the nuclear isoform of T cell protein tyrosine phosphatase (TC45) in nucleus. Here we show that β-arrestin1 directly interacts with STAT1 in nucleus after IFN-γ treatment and accelerates STAT1 tyrosine dephosphorylation by recruiting TC45. Consequently, β-arrestin1 negatively regulates STAT1 transcription activity as well as the IFN-γ-induced gene transcription. Application of β-arrestin1 siRNA significantly enhances IFN-γ-induced antiviral response in vesicular stomatitis virus (VSV)-infected cells. Our results reveal that nuclear β-arrestin1, acting as a scaffold for the dephosphorylation of STAT1, is an essential negative regulator of IFN-γ signaling and participates in the IFN-γ-induced cellular antiviral response. [Copyright &y& Elsevier]

Necroptosis induction in vitro often requires caspase-8 (Casp8) inhibition by zVAD because pro-Casp8 cleaves RIP1 to disintegrate the necrosome. It has been unclear how the Casp8 blockade of necroptosis is eliminated naturally. Here, we show that pro-Casp8 within the necrosome can be inactivated by phosphorylation at Thr265 (pC8T265). pC8T265 occurs in vitro in various necroptotic cells and in the cecum of TNF-treated mice. p90 RSK is the kinase of pro-Casp8. It is activated by a mechanism that does not need ERK but PDK1, which is recruited to the RIP1-RIP3-MLKL-containing necrosome. Phosphorylation of pro-Casp8 at Thr265 can substitute for zVAD to permit necroptosis in vitro. pC8T265 mimic T265E knockin mice are embryonic lethal due to unconstrained necroptosis, and the pharmaceutical inhibition of RSK-mediated pC8T265 diminishes TNF-induced cecum damage and lethality in mice by halting necroptosis. Thus, phosphorylation of pro-Casp8 at Thr265 by RSK is an intrinsic mechanism for passing the Casp8 checkpoint of necroptosis. • Phosphorylation of pro-caspase-8 at Thr265 releases the blockade of necroptosis • RSK phosphorylates pro-caspase-8 at Thr265 in the necrosome • PDK1 activates RSK by an ERK-independent mechanism to promote necroptosis • RSK inhibition protects mice from TNF-induced cecum injury and lethality An intrinsic mechanism—RSK, activated by TNF via PDK1—for overcoming necroptosis blockade is revealed by Yang et al. that phosphorylates pro-caspase-8 at Thr265 within the necrosome to inactivate pro-caspase-8. [ABSTRACT FROM AUTHOR]

Nucleoporins (Nups) are involved in neural development, and alterations in Nup genes are linked to human neurological diseases. However, physiological functions of specific Nups and the underlying mechanisms involved in these processes remain elusive. Here, we show that tissue-specific depletion of the nucleoporin Seh1 causes dramatic myelination defects in the CNS. Although proliferation is not altered in Seh1-deficient oligodendrocyte progenitor cells (OPCs), they fail to differentiate into mature oligodendrocytes, which impairs myelin production and remyelination after demyelinating injury. Genome-wide analyses show that Seh1 regulates a core myelinogenic regulatory network and establishes an accessible chromatin landscape. Mechanistically, Seh1 regulates OPCs differentiation by assembling Olig2 and Brd7 into a transcription complex at nuclear periphery. Together, our results reveal that Seh1 is required for oligodendrocyte differentiation and myelination by promoting assembly of an Olig2-dependent transcription complex and define a nucleoporin as a key player in the CNS. • Nucleoporin Seh1 is required for OPC differentiation • Seh1 is essential for CNS myelination and remyelination • Seh1 forms a complex with Olig2 at nuclear periphery • Seh1 recruits Olig2 and Brd7 to promote oligodendrocyte development Liu et al. demonstrate that the nucleoporin Seh1 functions in oligodendrocyte differentiation, myelination, and post-injury remyelination by assembling a Seh1/Olig2/Brd7 transcription complex at nuclear periphery. [ABSTRACT FROM AUTHOR]

Summary Astrocyte dysfunction and inflammation are associated with the pathogenesis of major depressive disorder (MDD). However, the mechanisms underlying these effects remain largely unknown. Here, we found that multiple endocrine neoplasia type 1 (Men1 ; protein: menin) expression is attenuated in the brain of mice exposed to CUMS (chronic unpredictable mild stress) or lipopolysaccharide. Astrocyte-specific reduction of Men1 (GcKO) led to depressive-like behaviors in mice. We observed enhanced NF-κB activation and IL-1β production with menin deficiency in astrocytes, where depressive-like behaviors in GcKO mice were restored by NF-κB inhibitor or IL-1β receptor antagonist. Importantly, we identified a SNP, rs375804228, in human MEN1 , where G503D substitution is associated with a higher risk of MDD onset. G503D substitution abolished menin-p65 interactions, thereby enhancing NF-κB activation and IL-1β production. Our results reveal a distinct astroglial role for menin in regulating neuroinflammation in depression, indicating that menin may be an attractive therapeutic target in MDD. Highlights • Astroglia menin deficiency leads to depressive-like behaviors in mice • Menin reduction in astrocytes promotes IL-1β generation through NF-κB activation • NF-κB and IL-1β inhibitors attenuate the depressive-like phenotypes • A MEN1 SNP associated with MDD risk leads to aberrant NF-κB activation Mechanisms underlying astrocyte-mediated neuroinflammation in depression remain unclear. Menin regulates NF-κB activity in astrocytes to promote neuroinflammation. Clinically, a MEN1 SNP is associated with the onset of depression. This study reveals a distinct role for menin in neuroinflammation and depression. [ABSTRACT FROM AUTHOR]