RelAp43, a member of the NF-κB family involved in innate immune response against Lyssavirus infection.

NF-κB transcription factors are crucial for many cellular processes. NF-κB is activated by viral infections to induce expression of antiviral cytokines. Here, we identified a novel member of the human NF-κB family, denoted RelAp43, the nucleotide sequence of which contains several exons as well as an intron of the RelA gene. RelAp43 is expressed in all cell lines and tissues tested and exhibits all the properties of a NF-κB protein. Although its sequence does not include a transactivation domain, identifying it as a class I member of the NF-κB family, it is able to potentiate RelA-mediated transactivation and stabilize dimers comprising p50. Furthermore, RelAp43 stimulates the expression of HIAP1, IRF1, and IFN-ß - three genes involved in cell immunity against viral infection. It is also targeted by the matrix protein of lyssaviruses, the agents of rabies, resulting in an inhibition of the NF-κB pathway. Taken together, our data provide the description of a novel functional member of the NF-κB family, which plays a key role in the induction of anti-viral innate immune response.

Manipulations of spinal cord excitability evoke developmentally-dependent compensatory changes in the lamprey spinal cord.

We have examined homeostatic or compensatory plasticity evoked by tonic changes in spinal cord excitability in the lamprey, a model system for investigating spinal cord function. In larval animals, reducing excitability by incubating in tetrodotoxin or the glutamate receptor antagonists CNQX or CNQX/AP5 for 20-48 h resulted in a diverse set of cellular and synaptic changes that together were consistent with an increase in spinal cord excitability. Similar changes occurred to a tonic increase in excitation evoked by incubating in high potassium physiological solution (i.e. responses were unidirectional). We also examined developmental influences on these effects. In animals developing from the larval to adult form effects were reduced or absent, suggesting that at this stage the spinal cord was more tolerant of changes in activity levels. Responses had returned in adult animals, but they were now bi-directional (i.e. opposite effects were evoked by an increase or decrease in excitability). The spinal cord can thus monitor and adapt cellular and synaptic properties to tonic changes in excitability levels. This should be considered in analyses of spinal cord plasticity and injury.

[Small protein, important functions: the matrix protein of rhabdovirus]. / Petite protéine, grandes fonctions : la protéine de matrice des rhabdovirus.

The family Rhabdoviridae contains important pathogens of humans, livestocks or even crops. The matrix protein of rhabdovirus is a constituent of the virion, forming a layer between the viral envelope and the nucleocapsid. It is crucial for the bullet-like morphology of the virion. There is a strong structural convergence between the lyssavirus and vesiculovirus matrix proteins. These matrix proteins are able to self assemble to form non-covalent polymers, acting as a scaffold for the other components of the virion. The matrix protein of rhabdovirus also has non-structural functions within the viral cycle: it is involved in the expression and replication of the viral genome, and in the virion budding. Moreover, it is a key mediator of the interactions between the virus and the infected cell, even involved in the death of the cell. To conclude, the repertoire of the matrix protein of rhabdovirus functionalities keeps on expanding.

The matrix protein of rabies virus binds to RelAp43 to modulate NF-κB-dependent gene expression related to innate immunity.

The matrix (M) protein of wild isolates of rabies virus such as Tha (M-Tha) was previously shown to be able to interact with RelAp43, a protein of the NF-κB family, and to efficiently suppress NF-κB-dependent reporter gene expression, in contrast with the vaccine strain SAD. Here, we analyze the mechanisms involved in RelAp43-M protein interaction. We demonstrate that the central part of M-Tha, and the specific C-terminal region of RelAp43 are required for this interaction. Four differences in the corresponding amino acid sequences of the M-Tha and M-SAD are shown to be crucial for RelAp43 interaction and subsequent modulation of innate immune response. Furthermore, the capacity of M-Tha to interact with RelAp43 was shown to be crucial for the control of the expression of four genes (IFN, TNF, IL8 and CXCL2) during viral infection. These findings reveal that RelAp43 is a potent regulator of transcription of genes involved in innate immune response during rabies virus infection and that the M protein of wild isolates of rabies virus is a viral immune-modulatory factor playing an important role in this RelAp43-mediated host innate immunity response in contrast to M protein of vaccine strains, which have lost this property.