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Regulated stability of eukaryotic elongation factor 2 kinase requires intrinsic but not ongoing activity

Regulated stability of eukaryotic elongation factor 2 kinase requires intrinsic but not ongoing activity
Regulated stability of eukaryotic elongation factor 2 kinase requires intrinsic but not ongoing activity
Eukaryotic elongation factor 2 kinase (eEF2K) is an atypical protein kinase which negatively regulates protein synthesis, is activated under stress conditions and plays a role in cytoprotection, e.g. in cancer cells. It is regarded as a possible target for therapeutic intervention in solid tumours. Earlier studies showed that eEF2K is degraded by a proteasome-dependent pathway in response to genotoxic stress and that this requires a phosphodegron that includes an autophosphorylation site. Thus, application of eEF2K inhibitors would stabilize eEF2K, partially negating the effects of inhibiting its activity. In the present study, we show that under a range of other stress conditions, including acidosis or treatment of cells with 2-deoxyglucose, eEF2K is also degraded. However, in these settings, the previously identified phosphodegron is not required for its degradation. Nevertheless, kinase-dead and other activity-deficient mutants of eEF2K are stabilized, as is a mutant lacking a critical autophosphorylation site (Thr348 in eEF2K), which is thought to be required for eEF2K and other ?-kinases to achieve their active conformations. In contrast, application of small-molecule eEF2K inhibitors does not stabilize the protein. Our data suggest that achieving an active conformation, rather than eEF2K activity per se, is required for its susceptibility to degradation. Additional degrons and E3 ligases beyond those already identified are probably involved in regulating eEF2K levels. Our findings have significant implications for therapeutic targeting of eEF2K, e.g. in oncology.
autophosphorylation, ?-kinase, degradation, eukaryotic elongation, factor 2 kinase (eEF2K), phosphodegron
1470-8728
321-331
Wang, Xuemin
d6bb4eb2-5687-46ed-b770-cceb22fd792e
Xie, Jianling
547a1c25-893b-4804-b316-8ac81562acac
Regufe da Mota, Sergio
fe39404b-e413-4834-97c6-0f2204b500a9
Moore, Claire E.
b8a95de9-31ae-4ace-be94-20b0f7a41718
Proud, Christopher G.
59dabfc8-4b44-4be8-a17f-578a58550cb3
Wang, Xuemin
d6bb4eb2-5687-46ed-b770-cceb22fd792e
Xie, Jianling
547a1c25-893b-4804-b316-8ac81562acac
Regufe da Mota, Sergio
fe39404b-e413-4834-97c6-0f2204b500a9
Moore, Claire E.
b8a95de9-31ae-4ace-be94-20b0f7a41718
Proud, Christopher G.
59dabfc8-4b44-4be8-a17f-578a58550cb3

Wang, Xuemin, Xie, Jianling, Regufe da Mota, Sergio, Moore, Claire E. and Proud, Christopher G. (2015) Regulated stability of eukaryotic elongation factor 2 kinase requires intrinsic but not ongoing activity. Biochemical Journal, 467 (2), 321-331. (doi:10.1042/BJ20150089). (PMID:25670349)

Record type: Article

Abstract

Eukaryotic elongation factor 2 kinase (eEF2K) is an atypical protein kinase which negatively regulates protein synthesis, is activated under stress conditions and plays a role in cytoprotection, e.g. in cancer cells. It is regarded as a possible target for therapeutic intervention in solid tumours. Earlier studies showed that eEF2K is degraded by a proteasome-dependent pathway in response to genotoxic stress and that this requires a phosphodegron that includes an autophosphorylation site. Thus, application of eEF2K inhibitors would stabilize eEF2K, partially negating the effects of inhibiting its activity. In the present study, we show that under a range of other stress conditions, including acidosis or treatment of cells with 2-deoxyglucose, eEF2K is also degraded. However, in these settings, the previously identified phosphodegron is not required for its degradation. Nevertheless, kinase-dead and other activity-deficient mutants of eEF2K are stabilized, as is a mutant lacking a critical autophosphorylation site (Thr348 in eEF2K), which is thought to be required for eEF2K and other ?-kinases to achieve their active conformations. In contrast, application of small-molecule eEF2K inhibitors does not stabilize the protein. Our data suggest that achieving an active conformation, rather than eEF2K activity per se, is required for its susceptibility to degradation. Additional degrons and E3 ligases beyond those already identified are probably involved in regulating eEF2K levels. Our findings have significant implications for therapeutic targeting of eEF2K, e.g. in oncology.

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More information

Published date: 15 April 2015
Keywords: autophosphorylation, ?-kinase, degradation, eukaryotic elongation, factor 2 kinase (eEF2K), phosphodegron
Organisations: Molecular and Cellular

Identifiers

Local EPrints ID: 384627
URI: http://eprints.soton.ac.uk/id/eprint/384627
ISSN: 1470-8728
PURE UUID: f3cce9bc-5e37-41b3-871c-e5503ceca108
ORCID for Sergio Regufe da Mota: ORCID iD orcid.org/0000-0002-8127-5246

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Date deposited: 03 Dec 2015 16:19
Last modified: 14 Mar 2024 22:01

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Contributors

Author: Xuemin Wang
Author: Jianling Xie
Author: Sergio Regufe da Mota ORCID iD
Author: Claire E. Moore
Author: Christopher G. Proud

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