Dihydrosphingomyelin Impairs HIV-1 Infection by Rigidifying Liquid-Ordered Membrane Domains

The lateral organization of lipids in cell membranes is thought to regulate numerous cell processes. Most studies focus on the coexistence of two fluid phases, the liquid crystalline (ld) and the liquid-ordered (lo); the putative presence of gel domains (so) is not usually taken into account. We show that in phospholipid:sphingolipid:cholesterol mixtures, in which sphingomyelin (SM) promoted fluid lo domains, dihydrosphingomyelin (DHSM) tended to form rigid domains. Genetic and pharmacological blockade of the dihydroceramide desaturase (Des1), which replaced SM with DHSM in cultured cells, inhibited cell infection by replication-competent and -deficient HIV-1. Increased DHSM levels gave rise to more rigid membranes, resistant to the insertion of the gp41 fusion peptide, thus inhibiting viral-cell membrane fusion. These results clarify the function of dihydrosphingolipids in biological membranes and identify Des1 as a potential target in HIV-1 infection.We thank L. Martínez-Prat and E. Dalmau for technical help and C. Mark for editorial assistance. C.R.V. and J.M.M.-O. received predoctoral fellowships from the Portuguese Ministry of Science (MCTES) and the CSIC, respectively. This work was supported in part by the CSIC, the Foundation for Research and Prevention of AIDS in Spain (FIPSE), the Spanish Ministry of Science and Innovation (BFU2008-01637 (A.A.), BIO2008-00772 (J.L.N.), BFU2007-62062 (F.M.G.), SAF2008-00649 (S.M.), SAF2008-00706 (G.F.), SAF2007-64696 (J.M.-P.), the Spanish AIDS (RD006/0006) and RIER (RD08/0075/0007) Networks, the Generalitat of Catalunya (2009SRG-01072 to G.F.), and the European Union (CHAIN, FP7/2007-2013, 2233131; J.M.-P.), and FP6 (INNOCHEM, LSHB-CT-2005-518167) and e-rare (PI07/1314) programs to S.M.Peer reviewe