title: Bcl-xL and UVRAG cause a monomer-dimer switch in Beclin1.
abstract: Beclin1 has a key regulatory role in the initiation of autophagy and is a tumor suppressor. We have examined the interplay between viral or human Bcl-2-like proteins and UVRAG and their opposite effects on Beclin1. We show that Beclin1 forms a dimer in solution via its coiled-coil domain both in vivo and in vitro. Viral Bcl-2 binds independently to two sites on the Beclin1 dimer, one with high affinity and one with lower affinity, whereas human Bcl-x(L) binds both sites equally with relatively low affinity. UVRAG disrupts the Beclin1-dimer interface, forming a heterodimer with Beclin1, suggesting that this is how UVRAG causes its effects on Beclin1 to activate autophagy. Both Bcl-2-like proteins reduce the affinity of UVRAG for Beclin1 approximately 4-fold, suggesting that they stabilize the Beclin1 dimer. Moreover, coimmunoprecipitation assays show that UVRAG substantially reduces Beclin1 dimerization in vivo. These data explain the concentration-dependent interplay between Bcl-2, UVRAG, and Beclin1, as both tumor suppressors, UVRAG and Beclin1, have single-copy mutations in human cancers. Furthermore, our data suggest that an alternative strategy for developing anti-cancer compounds would be to disrupt the Beclin1-dimer interface.
authors.affiliation: Institute of Molecular and Cell Biology, 61 Biopolis Dr., Proteos, Singapore 138673.
authors.forename: Christian G
authors.initials: CG
authors.lastname: Noble
authors.forename: Jing-Ming
authors.initials: JM
authors.lastname: Dong
authors.forename: Edward
authors.initials: E
authors.lastname: Manser
authors.forename: Haiwei
authors.initials: H
authors.lastname: Song
mesh_terms: D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000737:chemistry*; D000071186:Beclin-1; D001665:Binding Sites; D019556:COS Cells; D002151:Calorimetry; D002522:Chlorocebus aethiops; D019281:Dimerization; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry*; D008954:Models, Biological; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D013816:Thermodynamics; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D051020:bcl-X Protein / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; D008565:Membrane Proteins; D025521:Tumor Suppressor Proteins; C408122:UVRAG protein, human; D051020:bcl-X Protein