The cellular endosomal sorting complex required for transport (ESCRT) was recently found to mediate important morphogenesis processes at the nuclear envelope (NE). We previously showed that the Epstein-Barr virus (EBV) BFRF1 protein recruits the ESCRT-associated protein Alix to modulate NE structure and promote EBV nuclear egress. Here, we uncover new cellular factors and mechanisms involved in this process. BFRF1-induced NE vesicles are similar to those observed following EBV reactivation. BFRF1 is ubiquitinated, and elimination of possible ubiquitination by either lysine mutations or fusion of a deubiquitinase hampers NE-derived vesicle formation and virus maturation. While it interacts with multiple Nedd4-like ubiquitin ligases, BFRF1 preferentially binds Itch ligase. We show that Itch associates with Alix and BFRF1 and is required for BFRF1-induced NE vesicle formation. Our data demonstrate that Itch, ubiquitin, and Alix control the BFRF1-mediated modulation of the NE and EBV maturation, uncovering novel regulatory mechanisms of nuclear egress of viral nucleocapsids. IMPORTANCEThe nuclear envelope (NE) of eukaryotic cells not only serves as a transverse scaffold for cellular processes, but also as a natural barrier for most DNA viruses that assemble their nucleocapsids in the nucleus. Previously, we showed that the cellular endosomal sorting complex required for transport (ESCRT) machinery is required for the nuclear egress of EBV. Here, we further report the molecular interplay among viral BFRF1, the ESCRT adaptor Alix, and the ubiquitin ligase Itch. We found that BFRF1-induced NE vesicles are similar to those observed following EBV reactivation. The lysine residues and the ubiquitination of BFRF1 regulate the formation of BFRF1-induced NE-derived vesicles and EBV maturation. During the process, a ubiquitin ligase, Itch, preferably associates with BFRF1 and is required for BFRF1-induced NE vesicle formation. Therefore, our data indicate that Itch, ubiquitin, and Alix control the BFRF1-mediated modulation of the NE, suggesting novel regulatory mechanisms for ESCRT-mediated NE modulation. T he eukaryotic nuclear envelope (NE) is a specialized compartment composed of double lipid-bilayer membranes and an underlying proteinaceous lamina network and connected by membrane-integrating nuclear pore complexes (NPCs) that selectively regulate the nucleocytoplasmic transport of macromolecules. The NE not only provides an intact meshwork to protect the genome's integrity from cytoplasmic insults, but also serves as a natural barrier against most DNA viruses that replicate their genomes within the nucleus (1). DNA viruses thus evolve various strategies to modify the NE for efficient material transport and nuclear egress of viral nucleocapsids.Epstein-Barr virus (EBV) is a gammaherpesvirus that infects most of the human population. After primary infection, EBV becomes latent in resting B cells and can be reactivated periodically for lytic replication and virus shedding. During lytic infection, several EBV gene pr...

Patterned spontaneous activity periodically displays in developing retinas termed retinal waves, essential for visual circuit refinement. In neonatal rodents, retinal waves initiate in starburst amacrine cells (SACs), propagating across retinal ganglion cells (RGCs), further through visual centers. Although these waves are shown temporally synchronized with transiently high PKA activity, the downstream PKA target important for regulating the transmission from SACs remains unidentified. A t-SNARE, synaptosome-associated protein of 25 kDa (SNAP-25/SN25), serves as a PKA substrate, implying a potential role of SN25 in regulating retinal development. Here, we examined whether SN25 in SACs could regulate wave properties and retinogeniculate projection during development. In developing SACs, overexpression of wild-type SN25b, but not the PKA-phosphodeficient mutant (SN25b-T138A), decreased the frequency and spatial correlation of wave-associated calcium transients. Overexpressing SN25b, but not SN25b-T138A, in SACs dampened spontaneous, wave-associated, postsynaptic currents in RGCs and decreased the SAC release upon augmenting the cAMP-PKA signaling. These results suggest that SN25b overexpression may inhibit the strength of transmission from SACs via PKA-mediated phosphorylation at T138. Moreover, knockdown of endogenous SN25b increased the frequency of wave-associated calcium transients, supporting the role of SN25 in restraining wave periodicity. Finally, the eye-specific segregation of retinogeniculate projection was impaired by in vivo overexpression of SN25b, but not SN25b-T138A, in SACs. These results suggest that SN25 in developing SACs dampens the spatiotemporal properties of retinal waves and limits visual circuit refinement by phosphorylation at T138. Therefore, SN25 in SACs plays a profound role in regulating visual circuit refinement.

Spontaneous exocytosis of single synaptic vesicles generates miniature synaptic currents, which provide a window into the dynamic control of synaptic transmission. To resolve the impact of different factors on the dynamics and variability of synaptic transmission, we recorded miniature excitatory postsynaptic currents (mEPSCs) from cocultures of mouse hippocampal neurons with HEK cells expressing the postsynaptic proteins GluA2, neuroligin 1, PSD-95, and stargazin. Synapses between neurons and these heterologous cells have a molecularly defined postsynaptic apparatus, while the compact morphology of HEK cells eliminates the distorting effect of dendritic filtering. HEK cells in coculture produced mEPSCs with a higher frequency, larger amplitude, and more rapid rise and decay than neurons from the same culture. However, mEPSC area indicated that nerve terminals in synapses with both neurons and HEK cells release similar populations of vesicles. Modulation by the glutamate receptor ligand aniracetam revealed receptor contributions to mEPSC shape. Dendritic cable effects account for the slower mEPSC rise in neurons, whereas the slower decay also depends on other factors. Lastly, expression of synaptobrevin transmembrane domain mutants in neurons slowed the rise of HEK cell mEPSCs, thus revealing the impact of synaptic fusion pores. In summary, we show that cocultures of neurons with heterologous cells provide a geometrically simplified and molecularly defined system to investigate the time course of synaptic transmission and to resolve the contribution of vesicles, fusion pores, dendrites, and receptors to this process.

The cochlear nuclei (CN) receive sensory information from the ear and perform fundamental computations before relaying this information to higher processing centers. These computations are performed by distinct types of neurons interconnected in circuits dedicated to the specialized roles of the auditory system. In the present study we explored the use of voltage imaging to investigate CN circuitry. We tested two approaches based on fundamentally different voltage sensing technologies. Using a voltage-sensitive dye we recorded glutamate receptor-independent signals arising predominantly from axons. The mean conduction velocity of these fibers of 0.27 m/sec was rapid but in range with other unmyelinated axons. We then used a genetically-encoded hybrid voltage sensor (hVOS) to image voltage from a specific population of neurons. Probe expression was controlled using Cre recombinase linked toc-fosactivation. This activity-induced gene enabled targeting of neurons that are activated when a mouse hears a pure 15 kHz tone. In CN slices from these animals auditory nerve fiber stimulation elicited a glutamate receptor-dependent depolarization in hVOS probe-labeled neurons. These cells resided within a band corresponding to an isofrequency lamina, and responded with a high degree of synchrony. In contrast to the axonal origin of voltage-sensitive dye signals, hVOS signals represent predominantly post-synaptic responses. The introduction of voltage imaging to the CN creates the opportunity to investigate auditory processing circuitry in populations of neurons targeted on the basis of their genetic identity and their roles in sensory processing.Significance StatementThe cochlear nucleus uses dedicated circuitry to process and interpret information from the ear. This circuitry is organized tonotopically into laminae, each containing cells with an optimal sensitivity to a specific sound frequency. By targeting a genetically-encoded hybrid voltage sensor (hVOS) to identify neurons activated during the presentation of sound, the properties and function of these neurons become accessible to study in slices of mouse ventral cochlear nucleus. Imaging hVOS signals in these slices recapitulated the tonotopic organization. Imaging with a voltage sensitive dye provided a contrasting global view of signals arising predominantly from unmyelinated axons creating a potential method for studying type II auditory nerve or DCN parallel fibers.

Prevalence of asthma is increased all over the world, especially in Taiwan, study analyzed data of 997,729 enrolees from the National Health Insurance register from 2000 to 2007, the prevalence of asthma increase from 2.9% to 11.9%. Various signaling pathways and mechanisms have been identified and targeted for therapeutic application. Among them, one treatment, based on the use of MANS peptide, which is corresponding to the myristoylated N-terminal 24-amino acid portion of the MARCKS (myristoylated alanine-rich C kinase substrates) protein, to compete MARCKS’ binding to membrane has produced useful results. There is a lack of information regarding to the level/activity of phosphorylated MARCKS (p-MARCKS) in allergic asthma. It is also unclear if this activity can be directly suppressed for the allergic asthma treatment application. In this study, we have found elevated p-MARCKS in most of asthmatic tissues from human as well as from the animal model. This elevation can be directly suppressed by a peptide, MPS, targeting MARCKS phosphorylation site domain, prior to allergen sensitization. In addition, MPS pre-treatment also suppressed all of the symptoms associated with allergic airway asthma, which includes a reduction of inflammatory cells influx and TH2 cytokine presence in the lumen, and also a reduction of airway mucous cell metaplasia and airway hyperreactivity. In addition to inhibition of TH2 responses, lung dendritic cells migrate to mediastinal lymph nodes also decreased by MPS treatment. These results suggest that MARCKS phosphorylation site domain is a potential therapeutic target for the treatment of allergic asthma.