Pires Ricardo, Hartlieb Bettina, Signor Luca, Schoehn Guy, Lata Suman, Roessle Manfred, Moriscot Christine, Popov Sergei, Hinz Andreas, Jamin Marc, Boyer Veronique, Sadoul Remy, Forest Eric, Svergun Dmitri I, Göttlinger Heinrich G, Weissenhorn Winfried
Unit of Virus Host Cell Interactions (UVHCI) UMI 3265, Université Joseph Fourier-EMBL-CNRS, 6 rue Jules Horowitz, 38042 Grenoble, Cedex 9, France.
Structure. 2009 Jun 10;17(6):843-56. doi: 10.1016/j.str.2009.04.007.
ALIX recruits ESCRT-III CHMP4 and is involved in membrane remodeling during endosomal receptor sorting, budding of some enveloped viruses, and cytokinesis. We show that ALIX dimerizes via the middle domain (ALIX(-V)) in solution. Structural modeling based on small angle X-ray scattering (SAXS) data reveals an elongated crescent-shaped conformation for dimeric ALIX lacking the proline-rich domain (ALIX(BRO1-V)). Mutations at the dimerization interface prevent dimerization and induce an open elongated monomeric conformation of ALIX(-V) as determined by SAXS modeling. ALIX dimerizes in vivo and dimeric ALIX colocalizes with CHMP4B upon coexpression. We show further that ALIX dimerization affects HIV-1 budding. C-terminally truncated activated CHMP4B retaining the ALIX binding site forms linear, circular, and helical filaments in vitro, which can be bridged by ALIX. Our data suggest that dimeric ALIX represents the active form that interacts with ESCRT-III CHMP4 polymers and functions as a scaffolding protein during membrane remodeling processes.
ALIX招募ESCRT-III CHMP4，并参与内体受体分选、某些包膜病毒出芽和胞质分裂过程中的膜重塑。我们发现，ALIX在溶液中通过中间结构域（ALIX(-V)）形成二聚体。基于小角X射线散射（SAXS）数据的结构建模揭示了缺乏富含脯氨酸结构域的二聚体ALIX（ALIX(BRO1-V)）呈拉长的新月形构象。通过SAXS建模确定，二聚化界面处的突变会阻止二聚化，并诱导ALIX(-V)形成开放的拉长单体构象。ALIX在体内形成二聚体，共表达时二聚体ALIX与CHMP4B共定位。我们进一步表明，ALIX二聚化影响HIV-1出芽。保留ALIX结合位点的C末端截短的活化CHMP4B在体外形成线性、圆形和螺旋状细丝，这些细丝可由ALIX桥接。我们的数据表明，二聚体ALIX代表与ESCRT-III CHMP4聚合物相互作用的活性形式，并在膜重塑过程中作为支架蛋白发挥作用。
