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The proteasome inhibitor, MG132, promotes the reprogramming of translation in C2C12 myoblasts and facilitates the association of hsp25 with the eIF4F complex

The proteasome inhibitor, MG132, promotes the reprogramming of translation in C2C12 myoblasts and facilitates the association of hsp25 with the eIF4F complex
The proteasome inhibitor, MG132, promotes the reprogramming of translation in C2C12 myoblasts and facilitates the association of hsp25 with the eIF4F complex
The eukaryotic translation initiation factor (eIF) 4E, is regulated by modulating both its phosphorylation and its availability to interact with the scaffold protein, eIF4G, to form the mature eIF4F complex. Here we show that treatment of C2C12 myoblasts with the proteasomal inhibitor, MG132 (N-carbobenzoxyl-Leu-Leu-leucinal), resulted in an early decrease in protein synthesis rates followed by a partial recovery, reflecting the reprogramming of translation. The early inhibition of protein synthesis was preceded by a transient increase in eIF2alpha phosphorylation, followed by a sustained increase in eIF4E phosphorylation. Inhibition of eIF4E phosphorylation with CGP57380 failed to prevent translational reprogramming or the moderate decrease in eIF4F complexes at later times. Prolonged incubation with MG132 resulted in the increased expression of heat shock protein (hsp)25, alphaB-crystallin and hsp70, with a population of hsp25 associating with the eIF4F complex in a p38 mitogen-activated protein kinase-dependent manner. Under these conditions, eIF4GI, and to a lesser extent eIF4E, re-localized from a predominantly cytoplasmic distribution to a more perinuclear and granular staining. Although MG132 had little effect on the colocalization of eIF4E and eIF4GI, it promoted the SB203580-sensitive association of eIF4GI and hsp25, an effect not observed with alphaB-crystallin. Addition of recombinant hsp25 to an in vitro translation assay resulted in stimulation of on-going translation and a moderate decrease in de novo translation, indicating that this modified eIF4F complex containing hsp25 has a role to play in recovery of mRNA translation following cellular stress.
eIF4G, MG132, C2C12, translation, hsp25
0014-2956
3596-3611
Cowan, Joanne L.
a34fc26a-e7a3-435f-85c8-4f196b1c8d63
Morley, Simon J
6d1f2ef0-4c65-4823-8b75-fe666ac4126a
Cowan, Joanne L.
a34fc26a-e7a3-435f-85c8-4f196b1c8d63
Morley, Simon J
6d1f2ef0-4c65-4823-8b75-fe666ac4126a

Cowan, Joanne L. and Morley, Simon J (2004) The proteasome inhibitor, MG132, promotes the reprogramming of translation in C2C12 myoblasts and facilitates the association of hsp25 with the eIF4F complex. European Journal of Biochemistry, 271 (17), 3596-3611. (doi:10.1111/j.0014-2956.2004.04306.x). (PMID:15317596)

Record type: Article

Abstract

The eukaryotic translation initiation factor (eIF) 4E, is regulated by modulating both its phosphorylation and its availability to interact with the scaffold protein, eIF4G, to form the mature eIF4F complex. Here we show that treatment of C2C12 myoblasts with the proteasomal inhibitor, MG132 (N-carbobenzoxyl-Leu-Leu-leucinal), resulted in an early decrease in protein synthesis rates followed by a partial recovery, reflecting the reprogramming of translation. The early inhibition of protein synthesis was preceded by a transient increase in eIF2alpha phosphorylation, followed by a sustained increase in eIF4E phosphorylation. Inhibition of eIF4E phosphorylation with CGP57380 failed to prevent translational reprogramming or the moderate decrease in eIF4F complexes at later times. Prolonged incubation with MG132 resulted in the increased expression of heat shock protein (hsp)25, alphaB-crystallin and hsp70, with a population of hsp25 associating with the eIF4F complex in a p38 mitogen-activated protein kinase-dependent manner. Under these conditions, eIF4GI, and to a lesser extent eIF4E, re-localized from a predominantly cytoplasmic distribution to a more perinuclear and granular staining. Although MG132 had little effect on the colocalization of eIF4E and eIF4GI, it promoted the SB203580-sensitive association of eIF4GI and hsp25, an effect not observed with alphaB-crystallin. Addition of recombinant hsp25 to an in vitro translation assay resulted in stimulation of on-going translation and a moderate decrease in de novo translation, indicating that this modified eIF4F complex containing hsp25 has a role to play in recovery of mRNA translation following cellular stress.

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More information

Published date: September 2004
Keywords: eIF4G, MG132, C2C12, translation, hsp25
Organisations: Molecular and Cellular

Identifiers

Local EPrints ID: 372743
URI: http://eprints.soton.ac.uk/id/eprint/372743
ISSN: 0014-2956
PURE UUID: 5d649065-cfe3-4f5c-912e-122acfd2e0ae

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Date deposited: 18 Dec 2014 13:26
Last modified: 15 Jul 2019 21:35

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Author: Joanne L. Cowan
Author: Simon J Morley

University divisions

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