title: Aurothiomalate inhibits transformed growth by targeting the PB1 domain of protein kinase Ciota.
abstract: We recently identified the gold compound aurothiomalate (ATM) as a potent inhibitor of the Phox and Bem1p (PB1)-PB1 domain interaction between protein kinase C (PKC) iota and the adaptor molecule Par6. ATM also blocks oncogenic PKCiota signaling and the transformed growth of human lung cancer cells. Here we demonstrate that ATM is a highly selective inhibitor of PB1-PB1 domain interactions between PKCiota and the two adaptors Par6 and p62. ATM has no appreciable inhibitory effect on other PB1-PB1 domain interactions, including p62-p62, p62-NBR1, and MEKK3-MEK5 interactions. ATM can form thio-gold adducts with cysteine residues on target proteins. Interestingly, PKCiota (and PKCzeta) contains a unique cysteine residue, Cys-69, within its PB1 domain that is not present in other PB1 domain containing proteins. Cys-69 resides within the OPR, PC, and AID motif of PKCiota at the binding interface between PKCiota and Par6 where it interacts with Arg-28 on Par6. Molecular modeling predicts formation of a cysteinyl-aurothiomalate adduct at Cys-69 that protrudes into the binding cleft normally occupied by Par6, providing a plausible structural explanation for ATM inhibition. Mutation of Cys-69 of PKCiota to isoleucine or valine, residues frequently found at this position in other PB1 domains, has little or no effect on the affinity of PKCiota for Par6 but confers resistance to ATM-mediated inhibition of Par6 binding. Expression of the PKCiota C69I mutant in human non-small cell lung cancer cells confers resistance to the inhibitory effects of ATM on transformed growth. We conclude that ATM inhibits cellular transformation by selectively targeting Cys-69 within the PB1 domain of PKCiota.
authors.affiliation: Department of Cancer Biology, Mayo Clinic College of Medicine, Jacksonville, Florida 32224, USA.
authors.forename: Eda
authors.initials: E
authors.lastname: Erdogan
authors.forename: Trond
authors.initials: T
authors.lastname: Lamark
authors.forename: Melody
authors.initials: M
authors.lastname: Stallings-Mann
authors.lastname: Lee Jamieson
authors.forename: Maurizio
authors.initials: M
authors.lastname: Pellecchia
authors.forename: Mauricio
authors.initials: M
authors.lastname: Pellechia
authors.forename: E Aubrey
authors.initials: EA
authors.lastname: Thompson
authors.forename: Terje
authors.initials: T
authors.lastname: Johansen
authors.forename: Alan P
authors.initials: AP
authors.lastname: Fields
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001665:Binding Sites; D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology; D002352:Carrier Proteins / Q000378:metabolism; D002471:Cell Transformation, Neoplastic / Q000187:drug effects*; D019281:Dimerization; D006052:Gold Sodium Thiomalate / Q000494:pharmacology*; D006801:Humans; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000737:chemistry; D008175:Lung Neoplasms / Q000473:pathology; D008969:Molecular Sequence Data; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000737:chemistry; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D000099293:Protein Kinase C-lambda
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D000970:Antineoplastic Agents; D002352:Carrier Proteins; D006052:Gold Sodium Thiomalate; D007527:Isoenzymes; D011493:Protein Kinase C; D000099293:Protein Kinase C-lambda; C499657:PARD6A protein, human