title: Negative regulation of mixed lineage kinase 3 by protein kinase B/AKT leads to cell survival.
abstract: Mixed lineage kinase 3 (MLK3) is a mitogen-activated protein kinase kinase kinase (MAPKKK) that activates c-jun N-terminal kinase (JNK) and can induce cell death in neurons. By contrast, the activation of phosphatidylinositol 3-kinase and AKT/protein kinase B (PKB) acts to suppress neuronal apoptosis. Here, we report a functional interaction between MLK3 and AKT1/PKBalpha. Endogenous MLK3 and AKT1 interact in HepG2 cells, and this interaction is regulated by insulin. The interaction domain maps to the C-terminal half of MLK3 (amino acids 511-847), and this region also contains a putative AKT phosphorylation consensus sequence. Endogenous JNK, MKK7, and MLK3 kinase activities in HepG2 cells are significantly attenuated by insulin treatment, whereas the phosphatidylinositol 3-kinase inhibitors LY294002 and wortmannin reversed the effect. Finally, MLK3-mediated JNK activation is inhibited by AKT1. AKT phosphorylates MLK3 on serine 674 both in vitro and in vivo. Furthermore, the expression of activated AKT1 inhibits MLK3-mediated cell death in a manner dependent on serine 674 phosphorylation. Thus, these data provide the first direct link between MLK3-mediated cell death and its regulation by a cell survival signaling protein, AKT1.
authors.affiliation: Division of Molecular Cardiology, Cardiovascular Research Institute, The Texas A&M University System Health Science Center, College of Medicine, Temple 76504, USA.
authors.forename: Manoj K
authors.initials: MK
authors.lastname: Barthwal
authors.forename: Pradeep
authors.initials: P
authors.lastname: Sathyanarayana
authors.forename: Chanakya N
authors.initials: CN
authors.lastname: Kundu
authors.forename: Basabi
authors.initials: B
authors.lastname: Rana
authors.forename: Anamika
authors.initials: A
authors.lastname: Pradeep
authors.forename: Chandan
authors.initials: C
authors.lastname: Sharma
authors.forename: James R
authors.initials: JR
authors.lastname: Woodgett
authors.forename: Ajay
authors.initials: A
authors.lastname: Rana
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002460:Cell Line; D002470:Cell Survival; D017931:DNA Primers; D006367:HeLa Cells; D006801:Humans; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism*; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D000097767:Mitogen-Activated Protein Kinase Kinase Kinase 11
chemical_list: D017931:DNA Primers; D020930:MAP Kinase Kinase Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D000097767:Mitogen-Activated Protein Kinase Kinase Kinase 11; C494918:AKT1 protein, human