Apoptosis-associated tyrosine kinase (AATYK) has differential Ca2+-dependent phosphorylation states in response to survival and apoptotic conditions in cerebellar granule cells.
In dissociated cultures of cerebellar granule cells, extracellular high potassium (HK) and low potassium (LK) concentrations control cell survival and apoptosis, respectively. Apoptosis-associated tyrosine kinase (AATYK) is up-regulated during the LK-induced apoptosis. Overexpression of wild-type AATYK, but not its kinase-deficient mutant, stimulates apoptosis in LK. In this study, we analyzed the relationship between the phosphorylation states of AATYK and the survival of granule cells. AATYK was hypophosphorylated in HK, whereas it was hyperphosphorylated in apoptotic LK. HK-dependent hypophosphorylation of AATYK was controlled by L-type voltage-dependent calcium channel-mediated Ca2+ influx followed by Ca2+-dependent protein phosphatase activity. However, LK-induced hyperphosphorylation of AATYK at multiple sites was blocked by kainate, lithium, and protein kinase C-delta inhibitor. AATYK phosphorylation was concurrent with c-Jun phosphorylation. In addition, mutations of AATYK on either the kinase domain or Ser-480, Ser-558, and Ser-566 residues suppressed the LK-induced hyperphosphorylation and apoptosis, suggesting the involvement of self-kinase activity and these Ser residues in this process. Our data therefore indicate that the phosphorylation states of AATYK are closely related to the HK-induced survival and LK-induced apoptosis of cerebellar granule cells.
Tomomura
Mineko
M
Laboratory for Molecular Neurogenesis, RIKEN Brain Science Institute, Wako, Saitama 351-0198, Japan. mtomomura@brain.riken.go.jp
Furuichi
Teiichi
T
D000818:Animals; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000502:physiology*; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002465:Cell Movement; D002470:Cell Survival; D002478:Cells, Cultured; D002531:Cerebellum / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008094:Lithium / Q000494:pharmacology; D051379:Mice; D009154:Mutation; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology*; D017434:Protein Structure, Tertiary; D011505:Protein-Tyrosine Kinases / Q000502:physiology*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D012694:Serine / Q000737:chemistry; D014635:Valproic Acid / Q000494:pharmacology
D051017:Apoptosis Regulatory Proteins; D015220:Calcium Channels; D004791:Enzyme Inhibitors; D016755:Proto-Oncogene Proteins c-jun; D012694:Serine; D014635:Valproic Acid; D008094:Lithium; C485554:Aatk protein, mouse; D011505:Protein-Tyrosine Kinases; D011188:Potassium; D002118:Calcium