title: Physiological involvement in pH signaling of Vps24-mediated recruitment of Aspergillus PalB cysteine protease to ESCRT-III.
abstract: Activation of the Aspergillus nidulans transcription factor PacC, which mediates ambient pH regulation of gene expression and is recruited to ESCRT-III by the Vps32-interacting scaffold PalA, involves its ambient pH-dependent C-terminal proteolysis. This reaction is almost certainly catalyzed by the PalB calpain-like protease. Here we show that PalB associates with membranes and interacts specifically and directly with ESCRT-III Vps24. The PalB N-terminal MIT domain and the Vps24 C-terminal MIM motif are necessary and sufficient for this interaction. PalB(DeltaMIT), a mutant PalB lacking the MIT domain is inefficiently recruited to membranes and impaired in PacC proteolytic processing. Notably, membrane recruitment is promoted and PacC processing largely restored by covalent attachment of Vps24 to mutant PalB(DeltaMIT). This is the first reported evidence that calpain-like recruitment to ESCRT-III lattices plays a physiological role. It unambiguously positions the calpain-like protease PalB within the ESCRT-III-associated pH signaling complex, underlines the positive role of ESCRT-III in ambient pH signal transduction, and suggests a possible mechanism for PalB activation.
authors.affiliation: Centro de Investigaciones Biológicas CSIC, Madrid 28040, Spain.
authors.forename: Olga
authors.initials: O
authors.lastname: Rodríguez-Galán
authors.forename: Antonio
authors.initials: A
authors.lastname: Galindo
authors.forename: América
authors.initials: A
authors.lastname: Hervás-Aguilar
authors.forename: Herbert N
authors.initials: HN
authors.lastname: Arst
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Peñalva
mesh_terms: D001233:Aspergillus nidulans / Q000235:genetics / Q000378:metabolism*; D003546:Cysteine Endopeptidases / Q000096:biosynthesis* / Q000235:genetics; D005656:Fungal Proteins / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D015966:Gene Expression Regulation, Fungal / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D021381:Protein Transport / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D005656:Fungal Proteins; D046912:Multiprotein Complexes; C092394:PacC protein, Aspergillus; D014157:Transcription Factors; D003546:Cysteine Endopeptidases; C097042:PalB protein, Aspergillus nidulans