HuR Mediates Changes in the Stability of AChR beta-Subunit mRNAs after Skeletal Muscle Denervation

作者：Joassard Olivier R; Belanger Guy; Karmouch Jennifer; Lunde John A; Shukla Anu H; Chopard Angele; Legay Claire; Jasmin Bernard J^*

来源：Journal of Neuroscience, 2015, 35(31): 10949-10962.

DOI：10.1523/JNEUROSCI.1043-15.2015

• AChR beta-subunit mRNA
• HuR
• p38 MAPK
• skeletal muscle denervation

Acetylcholine receptors (AChRs) are heteromeric membrane proteins essential for neurotransmission at the neuromuscular junction. Previous work showed that muscle denervation increases expression of AChR mRNAs due to transcriptional activation of AChR subunit genes. However, it remains possible that post-transcriptional mechanisms are also involved in controlling the levels of AChR mRNAs following denervation. We examined whether post-transcriptional events indeed regulate AChR beta-subunit mRNA sin response to denervation. First, in vitro stability assays revealed that the half-life of AChR beta-subunit mRNAs was increased in the presence of denervated muscle protein extracts. A bioinformatics analysis revealed the existence of a conserved AU-rich element (ARE) in the 3'-untranslated region (UTR) of AChR beta-subunit mRNA. Furthermore, denervation of mouse muscle injected with a luciferase reporter construct containing the AChR beta-subunit 3'UTR, caused an increase in luciferase activity. By contrast, mutation of this ARE prevented this increase. We also observed that denervation increased expression of the RNA-binding protein human antigen R (HuR) and induced its translocation to the cytoplasm. Importantly, HuR binds to endogenous AChR beta-subunit transcripts in cultured myotubes and in vivo, and this binding is increased in denervated versus innervated muscles. Finally, p38MAPK, a pathway known to activate HuR, was induced following denervation as a result of MKK3/6 activation and a decrease in MKP-1 expression, thereby leading to an increase in the stability of AChR beta-subunit transcripts. Together, these results demonstrate the important contribution of post-transcriptional events in regulating AChR beta-subunit mRNAs and point toward a central role for HuR in mediating synaptic gene expression.

• 出版日期2015-8-5