Cancer-associated mutations activate the nonreceptor tyrosine kinase Ack1.
Ack1 is a nonreceptor tyrosine kinase that participates in tumorigenesis, cell survival, and migration. Relatively little is known about the mechanisms that regulate Ack1 activity. Recently, four somatic missense mutations of Ack1 were identified in cancer tissue samples, but the effects on Ack1 activity, and function have not been described. These mutations occur in the N-terminal region, the C-lobe of the kinase domain, and the SH3 domain. Here, we show that the cancer-associated mutations increase Ack1 autophosphorylation in mammalian cells without affecting localization and increase Ack1 activity in immune complex kinase assays. The cancer-associated mutations potentiate the ability of Ack1 to promote proliferation and migration, suggesting that point mutation is a mechanism for Ack1 deregulation. We propose that the C-terminal Mig6 homology region (MHR) (residues 802-990) participates in inhibitory intramolecular interactions. The isolated kinase domain of Ack1 interacts directly with the MHR, and the cancer-associated E346K mutation prevents binding. Likewise, mutation of a key hydrophobic residue in the MHR (Phe(820)) prevents the MHR-kinase interaction, activates Ack1, and increases cell migration. Thus, the cancer-associated mutation E346K appears to destabilize an autoinhibited conformation of Ack1, leading to constitutively high Ack1 activity.
Prieto-Echagüe
Victoria
V
Department of Physiology and Biophysics, School of Medicine, Stony Brook University, Stony Brook, New York 11794, USA.
Gucwa
Azad
A
Craddock
Barbara P
BP
Brown
Deborah A
DA
Miller
W Todd
WT
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002448:Cell Adhesion; D002465:Cell Movement; D049109:Cell Proliferation; D002522:Chlorocebus aethiops; D005455:Fluorescent Antibody Technique; D006801:Humans; D047468:Immunoprecipitation; D051379:Mice; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics*; D041681:NIH 3T3 Cells; D009369:Neoplasms / Q000201:enzymology* / Q000235:genetics* / Q000473:pathology; D010766:Phosphorylation; D011487:Protein Conformation; D011505:Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013347:Subcellular Fractions; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; C484017:ERRFI1 protein, human; D012333:RNA, Messenger; D025521:Tumor Suppressor Proteins; D011505:Protein-Tyrosine Kinases; C403262:TNK2 protein, human