CaMKK2 kinase domain interacts with the autoinhibitory region through the N-terminal lobe including the RP insert

Biochim Biophys Acta Gen Subj. 2018 Oct;1862(10):2304-2313. doi: 10.1016/j.bbagen.2018.07.025. Epub 2018 Jul 24.

Abstract

Background: Calcium/calmodulin-dependent protein kinase kinase 2 (CaMKK2), a member of the Ca⁠2+/calmodulin-dependent kinase (CaMK) family, functions as an upstream activator of CaMKI, CaMKIV and AMP-activated protein kinase. Thus, CaMKK2 is involved in the regulation of several key physiological and pathophysiological processes. Previous studies have suggested that Ca2+/CaM binding may cause unique conformational changes in the CaMKKs compared with other CaMKs. However, the underlying mechanistic details remain unclear.

Methods: In this study, hydrogen-deuterium exchange coupled to mass spectrometry, time-resolved fluorescence spectroscopy, small-angle x-ray scattering and chemical cross-linking were used to characterize Ca2+/CaM binding-induced structural changes in CaMKK2.

Results: Our data suggest that: (i) the CaMKK2 kinase domain interacts with the autoinhibitory region (AID) through the N-terminal lobe of the kinase domain including the RP insert, a segment important for targeting downstream substrate kinases; (ii) Ca2+/CaM binding affects the structure of several regions surrounding the ATP-binding pocket, including the activation segment; (iii) although the CaMKK2:Ca2+/CaM complex shows high conformational flexibility, most of its molecules are rather compact; and (iv) AID-bound Ca2+/CaM transiently interacts with the CaMKK2 kinase domain.

Conclusions: Interactions between the CaMKK2 kinase domain and the AID differ from those of other CaMKs. In the absence of Ca2+/CaM binding the autoinhibitory region inhibits CaMKK2 by both blocking access to the RP insert and by affecting the structure of the ATP-binding pocket.

General significance: Our results corroborate the hypothesis that Ca2+/CaM binding causes unique conformational changes in the CaMKKs relative to other CaMKs.

Keywords: CaMKK; Calmodulin; Protein kinase; Protein-protein interaction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcium / metabolism*
  • Calcium-Calmodulin-Dependent Protein Kinase Kinase / antagonists & inhibitors
  • Calcium-Calmodulin-Dependent Protein Kinase Kinase / chemistry*
  • Calcium-Calmodulin-Dependent Protein Kinase Kinase / metabolism*
  • Calmodulin / metabolism*
  • Humans
  • Models, Molecular
  • Phosphorylation
  • Protein Binding
  • Protein Conformation
  • Protein Domains

Substances

  • Calmodulin
  • CAMKK2 protein, human
  • Calcium-Calmodulin-Dependent Protein Kinase Kinase
  • Calcium