Late cornified envelope 1C (LCE1C), a transcriptional target of TAp63 phosphorylated at T46/T281, interacts with PRMT5

Identification of novel pathways and immune profiles related to sarcopenia

Introduction

Sarcopenia is a progressive deterioration of skeletal muscle mass strength and function.

Methods

To uncover the underlying cellular and biological mechanisms, we studied the association between sarcopenia's three stages and the patient's ethnicity, identified a gene regulatory network based on motif enrichment in the upregulated gene set of sarcopenia, and compared the immunological landscape among sarcopenia stages.

Results

We found that sarcopenia (S) was associated with GnRH, neurotrophin, Rap1, Ras, and p53 signaling pathways. Low muscle mass (LMM) patients showed activated pathways of VEGF signaling, B-cell receptor signaling, ErbB signaling, and T-cell receptor signaling. Low muscle mass and physical performance (LMM_LP) patients showed lower enrichment scores in B-cell receptor signaling, apoptosis, HIF-1 signaling, and the adaptive immune response pathways. Five common genes among DEGs and the elastic net regression model, TTC39DP, SLURP1, LCE1C, PTCD2P1, and OR7E109P, were expressed between S patients and healthy controls. SLURP1 and LCE1C showed the highest expression levels among sarcopenic Chinese descent than Caucasians and Afro-Caribbeans. Gene regulatory analysis of top upregulated genes in S patients yielded a top-scoring regulon containing GATA1, GATA2, and GATA3 as master regulators and nine predicted direct target genes. Two genes were associated with locomotion: POSTN and SLURP1. TTC39DP upregulation was associated with a better prognosis and stronger immune profile in S patients. The upregulation of SLURP1 and LCE1C was associated with a worse prognosis and weaker immune profile.

Conclusion

This study provides new insight into sarcopenia's cellular and immunological prospects and evaluates the age and sarcopenia-related modifications of skeletal muscle.

Protein Arginine Methyltransferase 5 Functions via Interacting Proteins

The protein arginine methyltransferases (PRMTs) are involved in such biological processes as transcription regulation, DNA repair, RNA splicing, and signal transduction, etc. In this study, we mainly focused on PRMT5, a member of the type II PRMTs, which functions mainly alongside other interacting proteins. PRMT5 has been shown to be overexpressed in a wide variety of cancers and other diseases, and is involved in the regulation of Epstein-Barr virus infection, viral carcinogenesis, spliceosome, hepatitis B, cell cycles, and various signaling pathways. We analyzed the regulatory roles of PRMT5 and interacting proteins in various biological processes above-mentioned, to elucidate for the first time the interaction between PRMT5 and its interacting proteins. This systemic analysis will enrich the biological theory and contribute to the development of novel therapies.

The foggy world(s) of p63 isoform regulation in normal cells and cancer

The p53 family member p63 exists as two major protein variants (TAp63 and ΔNp63) with distinct expression patterns and functional properties. Whilst downstream target genes of p63 have been studied intensively, how p63 variants are themselves controlled has been relatively neglected. Here, we review advances in understanding ΔNp63 and TAp63 regulation, highlighting their distinct pathways. TAp63 has roles in senescence and metabolism, and in germ cell genome maintenance, where it is activated post-transcriptionally by phosphorylation cascades after DNA damage. The function and regulation of TAp63 in mesenchymal and haematopoietic cells is less clear but may involve epigenetic control through DNA methylation. ΔNp63 functions to maintain stem/progenitor cells in various epithelia and is overexpressed in squamous and certain other cancers. ΔNp63 is transcriptionally regulated through multiple enhancers in concert with chromatin modifying proteins. Many signalling pathways including growth factors, morphogens, inflammation, and the extracellular matrix influence ΔNp63 levels, with inconsistent results reported. There is also evidence for reciprocal regulation, including ΔNp63 activating its own transcription. ΔNp63 is downregulated during cell differentiation through transcriptional regulation, while post-transcriptional events cause proteasomal degradation. Throughout the review, we identify knowledge gaps and highlight discordances, providing potential explanations including cell-context and cell-matrix interactions. Identifying individual p63 variants has roles in differential diagnosis and prognosis, and understanding their regulation suggests clinically approved agents for targeting p63 that may be useful combination therapies for selected cancer patients. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.