Structure-function analysis of the interaction between Bax and the cytomegalovirus-encoded protein vMIA.
The viral mitochondrial inhibitor of apoptosis (vMIA) encoded by the human cytomegalovirus exerts cytopathic effects and neutralizes the proapoptotic endogenous Bcl-2 family member Bax by recruiting it to mitochondria, inducing its oligomerization and membrane insertion. Using a combination of computational modeling and mutational analyses, we addressed the structure-function relationship of the molecular interaction between the protein Bax and the viral antiapoptotic protein vMIA. We propose a model in which vMIA exhibits an overall fold similar to Bcl-X(L). In contrast to Bcl-X(L), however, this predicted conformation of vMIA does not bind to the BH3 domain of Bax and rather engages in electrostatic interactions that involve a stretch of amino acids between the BH3 and BH2 domains of Bax and an alpha-helical domain located within the previously defined Bax-binding domain of vMIA, between the putative BH1-like and BH2-like domains. According to this model, vMIA is likely to bind Bax preferentially in its membrane-inserted conformation. The capacity of vMIA to cause fragmentation of the mitochondrial network and disorganization of the actin cytoskeleton is independent of its Bax-binding function. We found that Delta131-147 vMIA mutant, which lacks both the Bax-binding function and cell-death suppression but has intact mitochondria-targeting capacity, is similar to vMIA in its ability to disrupt the mitochondrial network and to disorganize the actin cytoskeleton. vMIADelta131-147 is a dominant-negative inhibitor of the antiapoptotic function of wild-type vMIA. Our experiments with vMIADelta131-147 suggest that vMIA forms homo-oligomers, which may engage in cooperative and/or multivalent interactions with Bax, leading to its functional neutralization.
Pauleau
A-L
AL
INSERM, U848, Pavillion de Recherche 1, Villejuif, France.
Larochette
N
N
Giordanetto
F
F
Scholz
S R
SR
Poncet
D
D
Zamzami
N
N
Goldmacher
V S
VS
Kroemer
G
G
D000595:Amino Acid Sequence; D017209:Apoptosis / Q000235:genetics; D001665:Binding Sites / Q000235:genetics; D003587:Cytomegalovirus / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D019281:Dimerization; D006367:HeLa Cells; D006801:Humans; D017874:Immediate-Early Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051034:Inhibitor of Apoptosis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D008928:Mitochondria / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D011485:Protein Binding / Q000235:genetics; D011487:Protein Conformation; D017384:Sequence Deletion / Q000235:genetics; D013329:Structure-Activity Relationship; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051028:bcl-2-Associated X Protein / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*
C494826:BAX protein, human; D017874:Immediate-Early Proteins; D051034:Inhibitor of Apoptosis Proteins; C420323:UL37 protein, Human herpesvirus 5; D014764:Viral Proteins; D051028:bcl-2-Associated X Protein