Activation of the nonreceptor protein tyrosine kinase Ack by multiple extracellular stimuli.
Ack/Ack1 is a nonreceptor protein tyrosine kinase that comprises a tyrosine kinase core, an SH3 domain, a Cdc42-binding region, a Ralt homology region, and a proline-rich region. Here we describe a detailed characterization of the Ack protein as well as the chromosomal localization of human Ack (chromosome 3q29) and the primary structure of murine Ack. We demonstrate that Ack is ubiquitously expressed, with highest expression seen in thymus, spleen, and brain. Activation of integrins by cell adhesion on fibronectin leads to strong tyrosine phosphorylation and activation of Ack. Upon cell stimulation with EGF or PDGF, Ack is tyrosine-phosphorylated and recruited to activated EGF or PDGF receptors, respectively. A pool of endogenous Ack molecules is constitutively tyrosine-phosphorylated, even in starved cells. Moreover, tyrosine-phosphorylated Ack forms a stable complex with the adapter protein Nck via its SH2 domain. Finally, we have characterized a membrane-targeting sterile alpha motif-like domain in the amino terminus of Ack. Using several Ack mutants, we show that the amino-terminal and CRIB domains are necessary for Ack autophosphorylation, whereas the SH3 domain appears to have an autoinhibitory role. These experiments suggest a functional role for Ack as an early transducer of multiple extracellular stimuli.
Galisteo
Maria L
ML
Department of Pharmacology, Yale University School of Medicine, New Haven, CT 06520, USA.
Yang
Yan
Y
Ureña
Jesus
J
Schlessinger
Joseph
J
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001921:Brain / Q000201:enzymology; D002448:Cell Adhesion; D002893:Chromosomes, Human, Pair 3 / Q000235:genetics; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005353:Fibronectins / Q000494:pharmacology; D006801:Humans; D048848:MAP Kinase Kinase Kinase 5 / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D015513:Oncogene Proteins / Q000378:metabolism; D010766:Phosphorylation; D020161:Physical Chromosome Mapping; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D017434:Protein Structure, Tertiary / Q000235:genetics; D015398:Signal Transduction; D013154:Spleen / Q000201:enzymology; D013950:Thymus Gland / Q000201:enzymology
D048868:Adaptor Proteins, Signal Transducing; D005353:Fibronectins; C078332:Nck protein; D015513:Oncogene Proteins; D010982:Platelet-Derived Growth Factor; D004815:Epidermal Growth Factor; D048848:MAP Kinase Kinase Kinase 5; C482858:MAP3K5 protein, human; C482859:Map3k5 protein, mouse