Recent work indicates that the LKB1 tumour suppressor protein kinase, which is mutated in Peutz–Jeghers cancer syndrome, phosphorylates and activates a group of protein kinases that are related to AMPK (AMP-activated protein kinase). Ten of the 14 AMPK-related protein kinases activated by LKB1, including SIK (salt-induced kinase), MARK (microtubule-affinity-regulating kinase) and BRSK (brain-specific kinase) isoforms, possess a ubiquitin-associated (UBA) domain immediately C-terminal to the kinase catalytic domain. These are the only protein kinases in the human genome known to possess a UBA domain, but their roles in regulating AMPK-related kinases are unknown. We have investigated the roles that the UBA domain may play in regulating these enzymes. Limited proteolysis of MARK2 revealed that the kinase and UBA domains were contained within a fragment that was resistant to trypsin proteolysis. SAXS (small-angle X-ray scattering) analysis of inactive and active LKB1-phosphorylated MARK2 revealed that activation of MARK2 is accompanied by a significant conformational change that alters the orientation of the UBA domain with respect to the catalytic domain. Our results indicate that none of the UBA domains found in AMPK-related kinases interact with polyubiquitin or other ubiquitin-like molecules. Instead, the UBA domains appear to play an essential conformational role and are required for the LKB1-mediated phosphorylation and activation of AMPK-related kinases. This is based on the findings that mutation or removal of the UBA domains of several AMPK-related kinases, including isoforms of MARK, SIK and BRSK, markedly impaired the catalytic activity and LKB1-mediated phosphorylation of these enzymes. We also provide evidence that the UBA domains do not function as LKB1–STRAD (STE20-related adaptor)–MO25 (mouse protein 25) docking/interacting sites and that mutations in the UBA domain of SIK suppressed the ability of SIK to localize within punctate regions of the nucleus. Taken together, these findings suggest that the UBA domains of AMPK-related kinases play an important role in regulating the conformation, activation and localization of these enzymes.
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March 2006
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Research Article|
February 24 2006
The ubiquitin-associated domain of AMPK-related kinases regulates conformation and LKB1-mediated phosphorylation and activation
Mahaboobi Jaleel;
Mahaboobi Jaleel
1
*MRC Protein Phosphorylation Unit, MSI/WTB Complex, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, U.K.
1To whom correspondence should be addressed (email [email protected]).
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Fabrizio Villa;
Fabrizio Villa
*MRC Protein Phosphorylation Unit, MSI/WTB Complex, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, U.K.
†Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, U.K.
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Maria Deak;
Maria Deak
*MRC Protein Phosphorylation Unit, MSI/WTB Complex, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, U.K.
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Rachel Toth;
Rachel Toth
*MRC Protein Phosphorylation Unit, MSI/WTB Complex, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, U.K.
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Alan R. Prescott;
Alan R. Prescott
‡Division of Cell Biology and Immunology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, U.K.
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Daan M. F. van Aalten;
Daan M. F. van Aalten
†Division of Biological Chemistry and Molecular Microbiology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, Scotland, U.K.
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Dario R. Alessi
Dario R. Alessi
*MRC Protein Phosphorylation Unit, MSI/WTB Complex, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, U.K.
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Publisher: Portland Press Ltd
Received:
November 16 2005
Revision Received:
January 03 2006
Accepted:
January 06 2006
Accepted Manuscript online:
January 06 2006
Online ISSN: 1470-8728
Print ISSN: 0264-6021
The Biochemical Society, London
2006
Biochem J (2006) 394 (3): 545–555.
Article history
Received:
November 16 2005
Revision Received:
January 03 2006
Accepted:
January 06 2006
Accepted Manuscript online:
January 06 2006
Connected Content
A commentary has been published:
The ubiquitin-associated domain of AMPK-related protein kinases allows LKB1-induced phosphorylation and activation
Citation
Mahaboobi Jaleel, Fabrizio Villa, Maria Deak, Rachel Toth, Alan R. Prescott, Daan M. F. van Aalten, Dario R. Alessi; The ubiquitin-associated domain of AMPK-related kinases regulates conformation and LKB1-mediated phosphorylation and activation. Biochem J 15 March 2006; 394 (3): 545–555. doi: https://doi.org/10.1042/BJ20051844
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