Infectious Bursal Disease Virus, a Non-enveloped Virus, Possesses a Capsid-associated Peptide That Deforms and Perforates Biological Membranes

Marie Galloux (1) , Sonia Libersou (2) , Nelly Morellet (3) , Serge Bouaziz (4) , Bruno da Costa (1) , Malika Ouldali (5) , Jean Lepault (2) , Bernard Delmas (6)

1 VIM (UR 0892) - Unité de recherche Virologie et Immunologie Moléculaires
2 VMS - Virologie moléculaire et structurale
3 ICSN - Institut de Chimie des Substances Naturelles
4 UPCG - UMR_S 640/UMR 8151 - Unité de Pharmacologie Chimique et Génétique
5 I2BC - Institut de Biologie Intégrative de la Cellule
6 CLERSÉ - Centre Lillois d’Études et de Recherches Sociologiques et Économiques - UMR 8019

Double-stranded RNA (dsRNA) virions constitute transcriptionally competent machines that must translocate across cell membranes to function within the cytoplasm. The entry mechanism of such non-enveloped viruses is not well described. Birnaviruses are unique among dsRNA viruses because they possess a single shell competent for entry. We hereby report how infectious bursal disease virus, an avian birnavirus, can disrupt cell membranes and enter into its target cells. One of its four structural peptides, pep46 (a 46-amino acid amphiphilic peptide) deforms synthetic membranes and induces pores visualized by electron cryomicroscopy, having a diameter of less than 10 nm. Using both biological and synthetic membranes, the pore-forming domain of pep46 was identified as its N terminus moiety (pep22). The N and C termini of pep22 are shown to be accessible during membrane destabilization and pore formation. NMR studies show that pep46 inserted into micelles displays a cis-trans proline isomerization at position 16 that we propose to be associated to the pore formation process. Reverse genetic experiments confirm that the amphiphilicity and proline isomerization of pep46 are both essential to the viral cycle. Furthermore, we show that virus infectivity and its membrane activity (probably because of the release of pep46 from virions) are controlled differently by calcium concentration, suggesting that entry is performed in two steps, endocytosis followed by endosome permeabilization. Our findings reveal a possible entry pathway of infectious bursal disease virus: in endosomes containing viruses, the lowering of the calcium concentration promotes the release of pep46 that induces the formation of pores in the endosomal membrane.

Domaines: Biologie structurale [q-bio.BM]

Marie Galloux, Sonia Libersou, Nelly Morellet, Serge Bouaziz, Bruno da Costa, et al.. Infectious Bursal Disease Virus, a Non-enveloped Virus, Possesses a Capsid-associated Peptide That Deforms and Perforates Biological Membranes. Journal of Biological Chemistry, 2007, 282 (28), pp.20774-20784. ⟨10.1074/jbc.M701048200⟩. ⟨hal-02122529⟩