title: Blockade of the BAK hydrophobic groove by inhibitory phosphorylation regulates commitment to apoptosis.
abstract: The BCL-2 family protein BAK is a key regulator of mitochondrial apoptosis. BAK activation first involves N-terminal conformational changes that lead to the transient exposure of the BAK BH3 domain that then inserts into a hydrophobic groove on another BAK molecule to form symmetric dimers. We showed recently that post-translational modifications are important in the regulation of BAK conformational change and multimerization, with dephosphorylation at tyrosine 108 constituting an initial step in the BAK activation process. We now show that dephosphorylation of serine 117 (S117), located in the BAK hydrophobic groove, is also critical for BAK activation to proceed to completion. Phosphorylation of BAK at S117 has two important regulatory functions: first, it occludes the binding of BH3-containing peptides that bind to BAK causing activation and cytochrome c release from mitochondria; second, it prevents BAK-BH3:BAK-Groove interactions that nucleate dimer formation for subsequent multimerization. Hence, BH3-mediated BAK conformational change and subsequent BAK multimerization for cytochrome c release and cell death is intimately linked to, and dependent on, dephosphorylation at S117. Our study reveals important novel mechanistic and structural insights into the temporal sequence of events governing the process of BAK activation in commitment to cell death and how they are regulated.
authors.affiliation: Department of Oncology, Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom.
authors.forename: Abul
authors.initials: A
authors.lastname: Azad
authors.forename: Joanna
authors.initials: J
authors.lastname: Fox
authors.forename: Sabrina
authors.initials: S
authors.lastname: Leverrier
authors.forename: Alan
authors.initials: A
authors.lastname: Storey
mesh_terms: D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D004789:Enzyme Activation; D045325:HCT116 Cells; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008954:Models, Biological; D008958:Models, Molecular; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010766:Phosphorylation; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D055503:Protein Multimerization; D054648:Protein Phosphatase 2 / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism; D012694:Serine / Q000737:chemistry; D015398:Signal Transduction; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000737:chemistry / Q000378:metabolism*
chemical_list: C474007:Bax protein (53-86); C525690:PPP2R5A protein, human; D010446:Peptide Fragments; D011518:Proto-Oncogene Proteins; D016159:Tumor Suppressor Protein p53; D050998:bcl-2 Homologous Antagonist-Killer Protein; D012694:Serine; D045304:Cytochromes c; D054648:Protein Phosphatase 2; D053148:Caspase 3