title: PDK1 protein phosphorylation at Thr354 by murine protein serine-threonine kinase 38 contributes to negative regulation of PDK1 protein activity.
abstract: Murine protein serine-threonine kinase 38 (MPK38) is a member of the AMP-activated protein kinase-related serine/threonine kinase family, which acts as cellular energy sensors. In this study, MPK38-induced PDK1 phosphorylation was examined to elucidate the biochemical mechanisms underlying phosphorylation-dependent regulation of 3-phosphoinositide-dependent protein kinase-1 (PDK1) activity. The results showed that MPK38 interacted with and inhibited PDK1 activity via Thr(354) phosphorylation. MPK38-PDK1 complex formation was mediated by the amino-terminal catalytic kinase domain of MPK38 and the pleckstrin homology domain of PDK1. This activity was dependent on insulin, a PI3K/PDK1 stimulator, as well as various apoptotic stimuli, including TNF-α, H(2)O(2), thapsigargin, and ionomycin. MPK38 inhibited PDK1 activity in a kinase-dependent manner and alleviated PDK1-mediated suppression of TGF-β (or ASK1) signaling, probably via the phosphorylation of PDK1 at Thr(354). In addition, MPK38-mediated inhibition of PDK1 activity was accompanied by the modulation of PDK1 binding to its positive and negative regulators, serine/threonine kinase receptor-associated protein and 14-3-3, respectively. Together, these findings suggest an important role for MPK38-mediated phosphorylation of PDK1 in the negative regulation of PDK1 activity.
authors.affiliation: Department of Biochemistry, School of Life Sciences, Chungbuk National University, Cheongju 361-763, Republic of Korea. hyunha@chungbuk.ac.kr
authors.forename: Hyun-A
authors.initials: HA
authors.lastname: Seong
authors.forename: Haiyoung
authors.initials: H
authors.lastname: Jung
authors.forename: Ravi
authors.initials: R
authors.lastname: Manoharan
authors.forename: Hyunjung
authors.initials: H
authors.lastname: Ha
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D001483:Base Sequence; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D057809:HEK293 Cells; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D048848:MAP Kinase Kinase Kinase 5 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes / Q000235:genetics / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects / Q000502:physiology; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
chemical_list: D006861:Hydrogen Peroxide; D048848:MAP Kinase Kinase Kinase 5; D009097:Multienzyme Complexes; D016877:Oxidants; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D000081382:Pyruvate Dehydrogenase Acetyl-Transferring Kinase; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha; C000631429:PDK1 protein, human; C000631433:Pdk1 protein, mouse; C108524:Melk protein, mouse; C482859:Map3k5 protein, mouse