title: A Requirement for ZAK Kinase Activity in Canonical TGF-β Signaling.
abstract: The sterile alpha motif and leucine zipper containing kinase ZAK (AZK, MLT, MLK7), is a MAPK-kinase kinase (MKKK). Like most MAPKKKs which are known to activate the c-Jun. amino-terminal kinase (JNK) pathway, ZAK has been shown to participate in the transduction of Transforming growth factor-β (TGF-β)-mediated non-canonical signaling. A role for ZAK in SMAD-dependent, canonical TGF-β signaling has not been previously appreciated. Using a combination of functional genomics and biochemical techniques, we demonstrate that ZAK regulates canonical TGFβRI/II signaling in lung and breast cancer cell lines and may serve as a key node in the regulation of TGFBR kinase activity. Remarkably, we demonstrate that siRNA mediated depletion of ZAK strongly inhibited TGF-β dependent SMAD2/3 activation and subsequent promoter activation (SMAD binding element driven luciferase expression; SBE4-Luc). A ZAK specific inhibitor (DHP-2), dose-dependently activated the bioluminescent TGFBR-kinase activity reporter (BTR), blocked TGF-β induced SMAD2/3 phosphorylation and SBE4-Luc activation and cancer cell-invasion. In aggregate, these findings identify a novel role for the ZAK kinase in canonical TGF-β signaling and an invasive cancer cell phenotype thus providing a novel target for TGF-β inhibition.
authors: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48105, USA; Center for Molecular Imaging, University of Michigan, Ann Arbor, MI 48105, USA. Electronic address: shyamnya@med.umich.edu.
authors: Shyam
authors: S
authors: Nyati
authors: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48105, USA.
authors: Areeb
authors: A
authors: Chator
authors: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48105, USA.
authors: Katerina
authors: K
authors: Schinske
authors: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48105, USA.
authors: Brandon S
authors: BS
authors: Gregg
authors: Department of Radiology, University of Michigan, Ann Arbor, MI 48105, USA.
authors: Brian Dale
authors: BD
authors: Ross
authors: Department of Radiation Oncology, University of Michigan, Ann Arbor, MI 48105, USA; Center for Molecular Imaging, University of Michigan, Ann Arbor, MI 48105, USA; Department of Radiology, University of Michigan, Ann Arbor, MI 48105, USA. Electronic address: alnawaz@med.umich.edu.
authors: Alnawaz
authors: A
authors: Rehemtulla