SHIP1 is required for the formation of neutrophil extracellular traps in rheumatoid arthritis.

Aberrant neutrophil extracellular traps (NETs) are involved in the pathogenesis of rheumatoid arthritis (RA). However, the specific pathway leading to NET formation in RA is poorly understood. Therefore, therapies targeting NETs are not available in RA. In this study, we demonstrated Src homology 2 domain-containing inositol phosphatase-1 (SHIP1) function as a hub to regulate NETosis through SHIP1/ p38 MAPK/TNF-α pathway both in vitro and ex vivo and inhibiting SHIP1 expression ameliorated RA symptoms in vivo. Neutrophils from RA patients showed enhanced NETosis as well as increased SHIP1, p38 mitogen-activated protein kinase (MAPK) family expression and tumor necrosis factor-α (TNF-α) expression. Inhibiting SHIP1 in neutrophils using small molecules counteracted the above-mentioned dysregulations and resulted in decrease in NETosis, p38 expression and TNF-α concentration. Consistent with this, SHIP1 agonist led to upregulated p38MAPK and NET formation. Moreover, inhibiting SHIP1 in vivo led to decreased NETosis and showed beneficial therapeutic effects in Collagen-induced arthritis (CIA) mice. Taken together, these results indicated that activation of SHIP1/MAPK/TNF-α pathway was necessary for upregulated NETosis in RA, which provided evidence for targeting SHIP1 in RA treatment.

Missense Mutations of Codon 116 in the SOD1 Gene Cause Rapid Progressive Familial ALS and Predict Short Viability With PMA Phenotype.

Amyotrophic lateral sclerosis (ALS) is the most common form of motor neuron disease, characterized by a great variety of both clinical presentations and genetic causes. Previous studies had identified two different missense mutations in SOD1 (p.R116C and p.R116G) causing familial ALS. In this study, we report a novel heterozygous missense mutation in the SOD1 gene (p.R116S) in a family with inherited ALS manifested as fast-deteriorating pure lower motor neuron symptoms. The patient displayed similar clinical picture and prognostic value to previous reported cases with different R116 substitution mutations. Modeling of all R116 substitutions in the resolved SOD1 protein structure revealed a shared mechanism with destroyed hydrogen bonds between R116 and other two residues, which might lead to protein unfolding and oligomer formation, ultimately conferring neurotoxicity.

Correction: Extracellular phosphorylation of a receptor tyrosine kinase controls synaptic localization of NMDA receptors and regulates pathological pain.

[This corrects the article DOI: 10.1371/journal.pbio.2002457.].

Positive surface charge of GluN1 N-terminus mediates the direct interaction with EphB2 and NMDAR mobility.

Localization of the N-methyl-D-aspartate type glutamate receptor (NMDAR) to dendritic spines is essential for excitatory synaptic transmission and plasticity. Rather than remaining trapped at synaptic sites, NMDA receptors undergo constant cycling into and out of the postsynaptic density. Receptor movement is constrained by protein-protein interactions with both the intracellular and extracellular domains of the NMDAR. The role of extracellular interactions on the mobility of the NMDAR is poorly understood. Here we demonstrate that the positive surface charge of the hinge region of the N-terminal domain in the GluN1 subunit of the NMDAR is required to maintain NMDARs at dendritic spine synapses and mediates the direct extracellular interaction with a negatively charged phospho-tyrosine on the receptor tyrosine kinase EphB2. Loss of the EphB-NMDAR interaction by either mutating GluN1 or knocking down endogenous EphB2 increases NMDAR mobility. These findings begin to define a mechanism for extracellular interactions mediated by charged domains.

Extracellular phosphorylation of a receptor tyrosine kinase controls synaptic localization of NMDA receptors and regulates pathological pain.

Extracellular phosphorylation of proteins was suggested in the late 1800s when it was demonstrated that casein contains phosphate. More recently, extracellular kinases that phosphorylate extracellular serine, threonine, and tyrosine residues of numerous proteins have been identified. However, the functional significance of extracellular phosphorylation of specific residues in the nervous system is poorly understood. Here we show that synaptic accumulation of GluN2B-containing N-methyl-D-aspartate receptors (NMDARs) and pathological pain are controlled by ephrin-B-induced extracellular phosphorylation of a single tyrosine (p*Y504) in a highly conserved region of the fibronectin type III (FN3) domain of the receptor tyrosine kinase EphB2. Ligand-dependent Y504 phosphorylation modulates the EphB-NMDAR interaction in cortical and spinal cord neurons. Furthermore, Y504 phosphorylation enhances NMDAR localization and injury-induced pain behavior. By mediating inducible extracellular interactions that are capable of modulating animal behavior, extracellular tyrosine phosphorylation of EphBs may represent a previously unknown class of mechanism mediating protein interaction and function.

Anchoring and synaptic stability of PSD-95 is driven by ephrin-B3.

Organization of signaling complexes at excitatory synapses by membrane-associated guanylate kinase (MAGUK) proteins regulates synapse development, plasticity, senescence and disease. Post-translational modification of MAGUK family proteins can drive their membrane localization, yet it is unclear how these intracellular proteins are targeted to sites of synaptic contact. Here we show using super-resolution imaging, biochemical approaches and in vivo models that the trans-synaptic organizing protein ephrin-B3 controls the synaptic localization and stability of PSD-95 and links these events to changes in neuronal activity via negative regulation of a newly identified mitogen-associated protein kinase (MAPK)-dependent phosphorylation site on ephrin-B3, Ser332. Unphosphorylated ephrin-B3 was enriched at synapses, and interacted directly with and stabilized PSD-95 at synapses. Activity-induced phosphorylation of Ser332 dispersed ephrin-B3 from synapses, prevented the interaction with PSD-95 and enhanced the turnover of PSD-95. Thus, ephrin-B3 specifies the synaptic localization of PSD-95 and likely links the synaptic stability of PSD-95 to changes in neuronal activity.