MYLPF

MuRF1 (Muscle-specific RING finger protein 1; gene name TRIM63) is a ubiquitin E3 ligase, associated with the progression of muscle atrophy. As a RING (Really Interesting New Gene) type E3 ligase, its unique activity of ubiquitylation is driven by a specific interaction with a UBE2 (ubiquitin conjugating enzyme). Our understanding of MuRF1 function remains unclear as candidate UBE2s have not been fully elucidated. In the present study, we screened human ubiquitin dependent UBE2s in vitro and found that MuRF1 engages in ubiquitylation with UBE2D, UBE2E, UBE2N/V families and UBE2W. MuRF1 can cause mono-ubiquitylation, K48- and K63-linked polyubiquitin chains in a UBE2 dependent manner. Moreover, we identified a two-step UBE2 dependent mechanism whereby MuRF1 is monoubiquitylated by UBE2W which acts as an anchor for UBE2N/V to generate polyubiquitin chains. With the in vitro ubiquitylation assay, we also found that MuRF2 and MuRF3 not only share the same UBE2 partners as MuRF1 but can also directly ubiquitylate the same substrates: Titin (A168-A170), Desmin, and MYLPF (Myosin Light Chain, Phosphorylatable, Fast Skeletal Muscle; also called Myosin Light Regulatory Chain 2). In summary, our work presents new insights into the mechanisms that underpin MuRF1 activity and reveals overlap in MuRF-induced ubiquitylation which could explain their partial redundancy in vivo.

To detect key genes of local glucocorticoid therapy in oral lichen planus (OLP) through transcriptome sequencing.

The study prospectively enrolled 28 symptomatic patients who visitied Department of Oral Mucosa, Peking University Hospital of Stomatology from November 2019 to March 2023. Topical inunction of 0.1 g/L of dexamethasone was applied for 1 min, 3 times daily for 4 weeks. The patients' signs and pain symptoms were recorded and they were classified as effective group and ineffective group according to the treatment outcome. Their mucosa samples were collected before treatment. After isolating total RNA, transcriptome sequencing was performed. The gene expression data obtained by sequencing were analyzed differently using the DESeq2 package in R software, and the Kyoto encyclopedia of genes and genomes (KEGG) pathway enrichment analysis was performed on the basis of the hypergeometric distribution algorithm to describe the biological function of differentially expressed genes (DEGs), accordingly detecting sensitivity related molecular affecting therapeutic effect of dexamethasone.

After 4 weeks treatment by topical dexamethasone, 13 cases of the 28 OLP patients responding well with the sign score reducing from 7.0 (4.5, 9.0) to 5.0 (3.0, 6.3), pain score decreasing from 5.0 (2.0, 5.5) to 2.0 (0.0, 3.5), oral health impact profile lessening from 5.0 (3.5, 9.0) to 1.0 (0.0, 5.0) significantly (P<0.01) were classified as effective group and 15 cases with poor response to the drug were sorted as ineffective group. There were no significant differences of demographic and baseline levels of clinical features, especially disease severity between these two groups. A total of 499 DEGs including 274 upregulated and 225 downregulated genes were identified between effective group and ineffective group. KEGG enrichment analysis showed that upregulated genes in effective group compared with ineffective group including CLDN8, CTNNA3, MYL2 and MYLPF were associated with leukocyte transendothelial migration, while downregulated genes were significantly enriched in tumor necrosis factor (TNF), interleukin-17 (IL-17), nuclear factor kappa B (NF-κB) signaling pathways, and cortisol synthesis and secretory.

High expressions of CLDN8, CTNNA3, MYL2 and MYLPF genes in patients with oral lichen planus have a good clinical response to topical dexamethasone, while patients with high expression genes of inflammation pathway such as TNF, IL-17, NF-κB and cortisol synthesis and secretion received poor effect.

Glucose is an important fuel for highly active skeletal muscles. Increased adenosine monophosphate (AMP)/adenosine triphosphate (ATP) ratios during repetitive contractions trigger AMP-activated protein kinase (AMPK), indicated by phosphorylation of AMPKα^Thr172, which promotes glucose uptake to support heightened energy needs, but it also suppresses anabolic processes. Inhibition of AMPK can occur by protein kinase B (AKT)-mediated phosphorylation of AMPKα^Ser485/491, releasing its brake on growth. The influence of insulin-like growth factor I (IGF-I) on glucose uptake and its interplay with AMPK activation is not well understood. Thus, the goal of this study was to determine if increased muscle IGF-I altered AMPKα phosphorylation and activity during muscle contraction. Adult male mice harboring the rat Igf1a cDNA regulated by the fast myosin light chain promoter (mIgf1^+/+) and wildtype littermates (WT) were used in the study. mIgf1^+/+ mice had enhanced glucose tolerance and insulin-stimulated glucose uptake, but similar exercise capacity. Fatiguing stimulations of extensor digitorum longus (EDL) muscles resulted in upregulated AMPKα phosphorylation at both Thr172 and Ser485/491 in WT and mIgf1^+/+ muscles. No differences in the phosphorylation response of the downstream AMPK target TBC1D1 were observed, but phosphorylation of raptor was significantly higher only in WT muscles. Further, total raptor content was elevated in mIgf1^+/+ muscles. The results show that high muscle IGF-I can enhance glucose uptake under resting conditions; however, in contracting muscle, it is not sufficient to inhibit AMPK activity.