title: Molecular mechanisms underlying the interaction of protein phosphatase-1c with ASPP proteins.
abstract: The serine/threonine PP-1c (protein phosphatase-1 catalytic subunit) is regulated by association with multiple regulatory subunits. Human ASPPs (apoptosis-stimulating proteins of p53) comprise three family members: ASPP1, ASPP2 and iASPP (inhibitory ASPP), which is uniquely overexpressed in many cancers. While ASPP2 and iASPP are known to bind PP-1c, we now identify novel and distinct molecular interactions that allow all three ASPPs to bind differentially to PP-1c isoforms and p53. iASPP lacks a PP-1c-binding RVXF motif; however, we show it interacts with PP-1c via a RARL sequence with a Kd value of 26 nM. Molecular modelling and mutagenesis of PP-1c-ASPP protein complexes identified two additional modes of interaction. First, two positively charged residues, Lys260 and Arg261 on PP-1c, interact with all ASPP family members. Secondly, the C-terminus of the PP-1c α, β and γ isoforms contain a type-2 SH3 (Src homology 3) poly-proline motif (PxxPxR), which binds directly to the SH3 domains of ASPP1, ASPP2 and iASPP. In PP-1cγ this comprises residues 309-314 (PVTPPR). When the Px(T)PxR motif is deleted or mutated via insertion of a phosphorylation site mimic (T311D), PP-1c fails to bind to all three ASPP proteins. Overall, we provide the first direct evidence for PP-1c binding via its C-terminus to an SH3 protein domain.
authors.affiliation: Department of Biochemistry, 3-37 Medical Sciences Building, School of Translational Medicine, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Canada, T6G 2H7.
authors.forename: Tamara D
authors.initials: TD
authors.lastname: Skene-Arnold
authors.forename: Hue Anh
authors.initials: HA
authors.lastname: Luu
authors.forename: R Glen
authors.initials: RG
authors.lastname: Uhrig
authors.forename: Veerle
authors.initials: V
authors.lastname: De Wever
authors.forename: Mhairi
authors.initials: M
authors.lastname: Nimick
authors.forename: Jason
authors.initials: J
authors.lastname: Maynes
authors.forename: Andrea
authors.initials: A
authors.lastname: Fong
authors.forename: Michael N G
authors.initials: MN
authors.lastname: James
authors.forename: Laura
authors.initials: L
authors.lastname: Trinkle-Mulcahy
authors.forename: Greg B
authors.initials: GB
authors.lastname: Moorhead
authors.forename: Charles F B
authors.initials: CF
authors.lastname: Holmes
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D051017:Apoptosis Regulatory Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs; D054645:Protein Phosphatase 1 / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D011817:Rabbits; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D020349:Surface Plasmon Resonance; D016159:Tumor Suppressor Protein p53 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D018909:src Homology Domains
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; D046912:Multiprotein Complexes; C498406:PPP1R13B protein, human; D011994:Recombinant Proteins; C495901:TP53 protein, human; C090468:TP53BP2 protein, human; D016159:Tumor Suppressor Protein p53; C517102:PPP1CC protein, human; D054645:Protein Phosphatase 1