AMP-activated protein kinase–mediated feedback phosphorylation controls the Ca2+/calmodulin (CaM) dependence of Ca2+/CaM-dependent protein kinase kinase β

Akihiro Nakanishi, Naoya Hatano, Yuya Fujiwara, Arian Sha’ri, Shota Takabatake, Hiroki Akano, Naoki Kanayama, Masaki Magari, Naohito Nozaki, Hiroshi Tokumitsu

Research output: Contribution to journalArticlepeer-review

18 Citations (Scopus)

Abstract

The Ca2+/calmodulin-dependent protein kinase kinase β (CaMKKβ)/5'-AMP–activated protein kinase (AMPK) phosphorylation cascade affects various Ca2+-dependent metabolic pathways and cancer growth. Unlike recombinant CaMKKβ that exhibits higher basal activity (autonomous activity), activation of the CaMKKβ/AMPK signaling pathway requires increased intracellular Ca2+ concentrations. Moreover, the Ca2+/ CaM dependence of CaMKKβ appears to arise from multiple phosphorylation events, including autophosphorylation and activities furnished by other protein kinases. However, the effects of proximal downstream kinases on CaMKKβ activity have not yet been evaluated. Here, we demonstrate feedback phosphorylation of CaMKKβ at multiple residues by CaMKKβ-activated AMPK in addition to autophosphorylation in vitro, leading to reduced autonomous, but not Ca2+/CaM-activated, CaMKKβ activity. MS analysis and site-directed mutagenesis of AMPK phosphorylation sites in CaMKKβ indicated that Thr144 phosphorylation by activated AMPK converts CaMKKβ into a Ca2+/CaM-dependent enzyme as shown by completely Ca2+/ CaM-dependent CaMKKβ activity of a phosphomimetic T144E CaMKKβ mutant. CaMKKβ mutant analysis indicated that the C-terminal domain (residues 471–587), including the autoinhibitory region, plays an important role in stabilizing an inactive conformation in a Thr144 phosphorylation– dependent manner. Furthermore, immunoblot analysis with anti-phospho-Thr144 antibody revealed phosphorylation of Thr144 in CaMKKβ in transfected COS-7 cells that was further enhanced by exogenous expression of AMPKα. These results indicate that AMPK-mediated feedback phosphorylation of CaMKKβ regulates the CaMKKβ/AMPK signaling cascade and may be physiologically important for intracellular maintenance of Ca2+-dependent AMPK activation by CaMKKβ.

Original languageEnglish
Pages (from-to)19804-19813
Number of pages10
JournalJournal of Biological Chemistry
Volume292
Issue number48
DOIs
Publication statusPublished - Dec 1 2017

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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