Increase in levels of polyubiquitin and proteasome mRNA in skeletal muscle during starvation and denervation atrophy

Most of the increased protein degradation in muscle atrophy caused by starvation and denervation is due to activation of a non-lysosomal ATP-dependent proteolytic process. To determine whether expression of the ubiquitin-proteasome-dependent pathway is activated in atrophying muscles, we measured th...

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Bibliographic Details
Published in:Biochemical journal 1995-05, Vol.307 ( Pt 3) (3), p.631-637
Main Authors: Medina, R, Wing, S S, Goldberg, A L
Format: Article
Language:English
Subjects:
Adenosine Triphosphate - metabolism
Animals
Biopolymers - biosynthesis
Biopolymers - genetics
Cysteine Endopeptidases - biosynthesis
Cysteine Endopeptidases - genetics
Endopeptidases - metabolism
Gene Expression
Heat-Shock Proteins - biosynthesis
Heat-Shock Proteins - genetics
Male
Multienzyme Complexes - biosynthesis
Multienzyme Complexes - genetics
Muscle Denervation
Muscle, Skeletal - innervation
Muscle, Skeletal - metabolism
Muscle, Skeletal - pathology
Muscular Atrophy - etiology
Muscular Atrophy - metabolism
Myocardium - metabolism
Myocardium - pathology
Polyubiquitin
Proteasome Endopeptidase Complex
Rats
Rats, Inbred Strains
RNA, Messenger - genetics
RNA, Messenger - metabolism
Space life sciences
Starvation - metabolism
Ubiquitins - biosynthesis
Ubiquitins - genetics
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Summary:Most of the increased protein degradation in muscle atrophy caused by starvation and denervation is due to activation of a non-lysosomal ATP-dependent proteolytic process. To determine whether expression of the ubiquitin-proteasome-dependent pathway is activated in atrophying muscles, we measured the levels of mRNA for ubiquitin (Ub) and proteasome subunits, and Ub content. After rats had been deprived of food for 1 or 2 days, the concentration of the two polyubiquitin (polyUb) transcripts increased 2-4-fold in the pale extensor digitorum longus muscle and 1-2.5-fold in the red soleus, whereas total muscle RNA and total mRNA content fell by 50%. After denervation of the soleus, there was a progressive 2-3-fold increase in polyUb mRNA for 1-3 days, whereas total RNA content fell. On starvation or denervation, Ub concentration in the muscles also rose by 60-90%. During starvation, polyUb mRNA levels also increased in heart, but not in liver, kidney, spleen, fat, brain or testes. Although the polyUb gene is a heat-shock gene that is induced in muscles under certain stressful conditions, the muscles of starving rats or after denervation did not express other heat-shock genes. On starvation or denervation, mRNA for several proteasome subunits (C-1, C-3, C-5, C-8 and C-9) also increased 2-4-fold in the atrophying muscles. When the food-deprived animals were re-fed, levels of Ub and proteasome mRNA in their muscles returned to control values within 1 day. In contrast, no change occurred in the levels of muscle mRNAs encoding cathepsin L, cathepsin D and calpain 1 on denervation or food deprivation. Thus polyUb and proteasome mRNAs increased in atrophying muscles in co-ordination with activation of the ATP-dependent proteolytic process.
ISSN:0264-6021
1470-8728
DOI:10.1042/bj3070631