Intrinsic membrane association of the cytoplasmic tail of influenza virus M2 protein and lateral membrane sorting regulated by cholesterol binding and palmitoylation

Bastian Thaa , Ilya Levental , Andreas Herrmann , Michael Veit (1)

1 Immunology and Molecular Biology

The influenza virus transmembrane protein M2 is a proton channel, but also plays a role in the scission of nascent virus particles from the plasma membrane. An amphiphilic helix in the cytoplasmic tail (CT) of M2 is supposed to insert into the lipid bilayer thereby inducing curvature. Palmitoylation of the helix and binding to cholesterol via putative CRAC (cholesterol recognition/interaction amino acid consensus) motifs are believed to target M2 to the edge of rafts, the viral budding site. We tested preconditions of this model, i.e. that the CT interacts with membranes and that acylation and cholesterol binding affect targeting of M2. M2-CT, purified as a glutathione-S-transferase fusion protein, associated with [³H]-photocholesterol and with liposomes. Mutation of tyrosines in the CRAC motifs prevented [³H]-photocholesterol labelling and reduced liposome binding. M2-CT fused to the yellow-fluorescent protein localized to the Golgi in transfected cells; membrane targeting was dependent on CRAC and (to a lesser extent) on palmitoylation. Preparation of giant plasma membrane vesicles from cells expressing full-length M2-GFP showed that the protein is partly present in the raft domain. Raft-targeting required palmitoylation, but not the CRAC motifs. Thus, palmitoylation and cholesterol binding affect the intrinsic membrane binding of the amphiphilic helix differentially.

Mots clés: Life Sciences

Bastian Thaa, Ilya Levental, Andreas Herrmann, Michael Veit. Intrinsic membrane association of the cytoplasmic tail of influenza virus M2 protein and lateral membrane sorting regulated by cholesterol binding and palmitoylation. Biochemical Journal, 2011, 437 (3), pp.389-397. ⟨10.1042/BJ20110706⟩. ⟨hal-00608382⟩