title: Mitotic phosphorylation rescues Abl from F-actin-mediated inhibition.
abstract: We have previously shown that F-actin exerts a negative effect on Abl tyrosine kinase activity. This inhibition results from a direct association of F-actin with the C terminus of Abl and accounts, in part, for the loss of Abl activity in detached fibroblasts. We report here that Abl from mitotic cells or cells treated with the protein phosphatase inhibitor okadaic acid remains active when detached from the extracellular matrix. Aspartic acid substitution of Thr(566), which is phosphorylated in mitotic or okadaic acid-treated cells, is sufficient to abolish F-actin-mediated inhibition and to maintain Abl activity despite cell detachment. A recent crystal structure of the Abl N-terminal region has revealed autoinhibitory interactions among the Src homology 3 (SH3), SH2, and kinase domains. We found that deletion of the SH2 domain also abolished the negative effect of F-actin on kinase activity. Immediately following the kinase domain in Abl is a proline-rich linker (PRL) that binds to several SH3 adaptor proteins. Interestingly, binding of the Crk N-terminal SH3 domain to the PRL also disrupted F-actin-mediated inhibition of Abl kinase. These results suggest that F-actin may reinforce the autoinhibitory interactions to regulate Abl kinase and that inhibition can be relieved through phosphorylation and/or protein interactions with the Abl PRL region.
authors.affiliation: Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, La Jolla, California 92037-1099, USA.
authors.forename: Pamela J
authors.initials: PJ
authors.lastname: Woodring
authors.forename: Tony
authors.initials: T
authors.lastname: Hunter
authors.forename: Jean Y J
authors.initials: JY
authors.lastname: Wang
mesh_terms: D000199:Actins / Q000737:chemistry / Q000378:metabolism*; D000495:Allosteric Site; D000595:Amino Acid Sequence; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry / Q000378:metabolism; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D047468:Immunoprecipitation; D051379:Mice; D008938:Mitosis; D008969:Molecular Sequence Data; D009154:Mutation; D041681:NIH 3T3 Cells; D019319:Okadaic Acid / Q000494:pharmacology; D010455:Peptides / Q000737:chemistry; D010590:Phalloidine / Q000494:pharmacology; D010766:Phosphorylation; D011108:Polymers / Q000737:chemistry; D011392:Proline / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016315:Proto-Oncogene Proteins c-abl / Q000378:metabolism*; D012319:RNA Polymerase II / Q000737:chemistry; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D013912:Threonine / Q000737:chemistry; D014162:Transfection; D014357:Trypsin / Q000737:chemistry; D018909:src Homology Domains
chemical_list: D000199:Actins; D004791:Enzyme Inhibitors; D010455:Peptides; D011108:Polymers; D011993:Recombinant Fusion Proteins; D010590:Phalloidine; D019319:Okadaic Acid; D013912:Threonine; D001224:Aspartic Acid; D011392:Proline; D005982:Glutathione Transferase; D016315:Proto-Oncogene Proteins c-abl; D012319:RNA Polymerase II; D014357:Trypsin