CPEB1 directs muscle stem cell activation by reprogramming the translational landscape

Wenshu Zeng,Kim S W Lam,Wai-Kin So,Wenxin Zhang,Lu Yue,Tom H Cheung,Erin H Y Tse

doi:10.1038/s41467-022-28612-1

Abstract

Skeletal muscle stem cells, also called Satellite Cells (SCs), are actively maintained in quiescence but can activate quickly upon extrinsic stimuli. However, the mechanisms of how quiescent SCs (QSCs) activate swiftly remain elusive. Here, using a whole mouse perfusion fixation approach to obtain bona fide QSCs, we identify massive proteomic changes during the quiescence-to-activation transition in pathways such as chromatin maintenance, metabolism, transcription, and translation. Discordant correlation of transcriptomic and proteomic changes reveals potential translational regulation upon SC activation. Importantly, we show Cytoplasmic Polyadenylation Element Binding protein 1 (CPEB1), post-transcriptionally affects protein translation during SC activation by binding to the 3′ UTRs of different transcripts. We demonstrate phosphorylation-dependent CPEB1 promoted Myod1 protein synthesis by binding to the cytoplasmic polyadenylation elements (CPEs) within its 3′ UTRs to regulate SC activation and muscle regeneration. Our study characterizes CPEB1 as a key regulator to reprogram the translational landscape directing SC activation and subsequent proliferation.

Highlights

Skeletal muscle stem cells, called Satellite Cells (SCs), are actively maintained in quiescence but can activate quickly upon extrinsic stimuli
From a whole proteome aspect, quiescent SCs (QSCs) differed from freshly isolated SCs (fiSCs) while QSCs and fiSCs were more distant from iASCs and cASCs, indicating a rapid and significant activation response of QSCs and, that the fixation approach can preserve the unique proteomic signature of QSCs in vivo (Fig. 1b, protein expression listed in Supplementary Data 1)
To investigate how the phosphorylation of Cytoplasmic Polyadenylation Element Binding protein 1 (CPEB1) is involved in translational regulation, we examined whether the phosphorylation mutant affects the capability of CPEB1 to bind mRNAs

Summary

Introduction

Called Satellite Cells (SCs), are actively maintained in quiescence but can activate quickly upon extrinsic stimuli. We demonstrate phosphorylation-dependent CPEB1 promoted Myod[1] protein synthesis by binding to the cytoplasmic polyadenylation elements (CPEs) within its 3′ UTRs to regulate SC activation and muscle regeneration. Myod[1] mRNA is expressed in QSCs while its translation is suppressed by RNA-binding protein Staufen-119. Upon injury, these inhibitions are relieved for rapid protein synthesis to drive SC activation[17–19]. How post-transcriptional regulation manipulates the global proteomics landscape to drive the SC quiescence-to-activation transition remains to be explored. The 3′ UTR of mRNA functions as a post-transcriptional regulation hotspot by harboring a series of motifs such as microRNA (miRNA) target sites, AU-rich elements (AREs), and polyadenylation signals (PASs)[20]. Different from miRNA target sites, AREs either induce or suppress protein translation depending on the function of the RNA-binding protein[22]. Alternative usage of PASs regulates the length of 3′ UTRs, resulting in a differential number of RNA-regulatory motifs, and varying levels of protein production[23]

Methods

Results

Conclusion