APOBEC2 safeguards skeletal muscle cell fate through binding chromatin and regulating transcription of non-muscle genes during myoblast differentiation.

The apolipoprotein B messenger RNA editing enzyme, catalytic polypeptide (APOBEC) family is composed of nucleic acid editors with roles ranging from antibody diversification to RNA editing. APOBEC2, a member of this family with an evolutionarily conserved nucleic acid-binding cytidine deaminase domain, has neither an established substrate nor function. Using a cellular model of muscle differentiation where APOBEC2 is inducibly expressed, we confirmed that APOBEC2 does not have the attributed molecular functions of the APOBEC family, such as RNA editing, DNA demethylation, and DNA mutation. Instead, we found that during muscle differentiation APOBEC2 occupied a specific motif within promoter regions; its removal from those regions resulted in transcriptional changes. Mechanistically, these changes reflect the direct interaction of APOBEC2 with histone deacetylase (HDAC) transcriptional corepressor complexes. We also found that APOBEC2 could bind DNA directly, in a sequence-specific fashion, suggesting that it functions as a recruiter of HDAC to specific genes whose promoters it occupies. These genes are normally suppressed during muscle cell differentiation, and their suppression may contribute to the safeguarding of muscle cell fate. Altogether, our results reveal a unique role for APOBEC2 within the APOBEC family.

Intramuscular injection of mesenchymal stem cells augments basal muscle protein synthesis after bouts of resistance exercise in male mice.

Skeletal muscle mass is critical for activities of daily living. Resistance training maintains or increases muscle mass, and various strategies maximize the training adaptation. Mesenchymal stem cells (MSCs) are multipotent cells with differential potency in skeletal muscle cells and the capacity to secrete growth factors. However, little is known regarding the effect of intramuscular injection of MSCs on basal muscle protein synthesis and catabolic systems after resistance training. Here, we measured changes in basal muscle protein synthesis, the ubiquitin-proteasome system, and autophagy-lysosome system-related factors after bouts of resistance exercise by intramuscular injection of MSCs. Mice performed three bouts of resistance exercise (each consisting of 50 maximal isometric contractions elicited by electrical stimulation) on the right gastrocnemius muscle every 48 h, and immediately after the first bout, mice were intramuscularly injected with either MSCs (2.0 × 106 cells) labeled with green fluorescence protein (GFP) or vehicle only placebo. Seventy-two hours after the third exercise bout, GFP was detected only in the muscle injected with MSCs with concomitant elevation of muscle protein synthesis. The injection of MSCs also increased protein ubiquitination. These results suggest that the intramuscular injection of MSCs augmented muscle protein turnover at the basal state after consecutive resistance exercise.

Differentiation and functioning of the lateral line organ in zebrafish require Smpx activity.

The small muscle protein, X-linked (SMPX) gene encodes a cytoskeleton-associated protein, highly expressed in the inner ear hair cells (HCs), possibly regulating auditory function. In the last decade, several mutations in SMPX have been associated with X-chromosomal progressive non syndromic hearing loss in humans and, in line with this, Smpx-deficient animal models, namely zebrafish and mouse, showed significant impairment of inner ear HCs development, maintenance, and functioning. In this work, we uncovered smpx expression in the neuromast mechanosensory HCs of both Anterior and Posterior Lateral Line (ALL and PLL, respectively) of zebrafish larvae and focused our attention on the PLL. Smpx was subcellularly localized throughout the cytoplasm of the HCs, as well as in their primary cilium. Loss-of-function experiments, via both morpholino-mediated gene knockdown and CRISPR/Cas9 F0 gene knockout, revealed that the lack of Smpx led to fewer properly differentiated and functional neuromasts, as well as to a smaller PLL primordium (PLLp), the latter also Smpx-positive. In addition, the kinocilia of Smpx-deficient neuromast HCs appeared structurally and numerically altered. Such phenotypes were associated with a significant reduction in the mechanotransduction activity of the neuromast HCs, in line with their positivity for Smpx. In summary, this work highlights the importance of Smpx in lateral line development and, specifically, in proper HCs differentiation and/or maintenance, and in the mechanotransduction process carried out by the neuromast HCs. Because lateral line HCs are both functionally and structurally analogous to the cochlear HCs, the neuromasts might represent an invaluable-and easily accessible-tool to dissect the role of Smpx in HCs development/functioning and shed light on the underlying mechanisms involved in hearing loss.

FBXO32-mediated degradation of PTEN promotes lung adenocarcinoma progression.

FBXO32, a member of the F-box protein family, is known to play both oncogenic and tumor-suppressive roles in different cancers. However, the functions and the molecular mechanisms regulated by FBXO32 in lung adenocarcinoma (LUAD) remain unclear. Here, we report that FBXO32 is overexpressed in LUAD compared with normal lung tissues, and high expression of FBXO32 correlates with poor prognosis in LUAD patients. Firstly, we observed with a series of functional experiments that FBXO32 alters the cell cycle and promotes the invasion and metastasis of LUAD cells. We further corroborate our findings using in vivo mouse models of metastasis and confirmed that FBXO32 positively regulates LUAD tumor metastasis. Using a proteomic-based approach combined with computational analyses, we found a positive correlation between FBXO32 and the PI3K/AKT/mTOR pathway, and identified PTEN as a FBXO32 interactor. More important, FBXO32 binds PTEN via its C-terminal substrate binding domain and we also validated PTEN as a bona fide FBXO32 substrate. Finally, we demonstrated that FBXO32 promotes EMT and regulates the cell cycle by targeting PTEN for proteasomal-dependent degradation. In summary, our study highlights the role of FBXO32 in promoting the PI3K/AKT/mTOR pathway via PTEN degradation, thereby fostering lung adenocarcinoma progression.

A novel gene-trap line reveals the dynamic patterns and essential roles of cysteine and glycine-rich protein 3 in zebrafish heart development and regeneration.

Mutations in cysteine and glycine-rich protein 3 (CSRP3)/muscle LIM protein (MLP), a key regulator of striated muscle function, have been linked to hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) in patients. However, the roles of CSRP3 in heart development and regeneration are not completely understood. In this study, we characterized a novel zebrafish gene-trap line, gSAIzGFFM218A, which harbors an insertion in the csrp3 genomic locus, heterozygous fish served as a csrp3 expression reporter line and homozygous fish served as a csrp3 mutant line. We discovered that csrp3 is specifically expressed in larval ventricular cardiomyocytes (CMs) and that csrp3 deficiency leads to excessive trabeculation, a common feature of CSRP3-related HCM and DCM. We further revealed that csrp3 expression increased in response to different cardiac injuries and was regulated by several signaling pathways vital for heart regeneration. Csrp3 deficiency impeded zebrafish heart regeneration by impairing CM dedifferentiation, hindering sarcomere reassembly, and reducing CM proliferation while aggravating apoptosis. Csrp3 overexpression promoted CM proliferation after injury and ameliorated the impairment of ventricle regeneration caused by pharmacological inhibition of multiple signaling pathways. Our study highlights the critical role of Csrp3 in both zebrafish heart development and regeneration, and provides a valuable animal model for further functional exploration that will shed light on the molecular pathogenesis of CSRP3-related human cardiac diseases.

Monocarboxylate transporter 4 deficiency enhances high-intensity interval training-induced metabolic adaptations in skeletal muscle.

High-intensity exercise stimulates glycolysis, subsequently leading to elevated lactate production within skeletal muscle. While lactate produced within the muscle is predominantly released into the circulation via the monocarboxylate transporter 4 (MCT4), recent research underscores lactate's function as an intercellular and intertissue signalling molecule. However, its specific intracellular roles within muscle cells remains less defined. In this study, our objective was to elucidate the effects of increased intramuscular lactate accumulation on skeletal muscle adaptation to training. To achieve this, we developed MCT4 knockout mice and confirmed that a lack of MCT4 indeed results in pronounced lactate accumulation in skeletal muscle during high-intensity exercise. A key finding was the significant enhancement in endurance exercise capacity at high intensities when MCT4 deficiency was paired with high-intensity interval training (HIIT). Furthermore, metabolic adaptations supportive of this enhanced exercise capacity were evident with the combination of MCT4 deficiency and HIIT. Specifically, we observed a substantial uptick in the activity of glycolytic enzymes, notably hexokinase, glycogen phosphorylase and pyruvate kinase. The mitochondria also exhibited heightened pyruvate oxidation capabilities, as evidenced by an increase in oxygen consumption when pyruvate served as the substrate. This mitochondrial adaptation was further substantiated by elevated pyruvate dehydrogenase activity, increased activity of isocitrate dehydrogenase - the rate-limiting enzyme in the TCA cycle - and enhanced function of cytochrome c oxidase, pivotal to the electron transport chain. Our findings provide new insights into the physiological consequences of lactate accumulation in skeletal muscle during high-intensity exercises, deepening our grasp of the molecular intricacies underpinning exercise adaptation. KEY POINTS: We pioneered a unique line of monocarboxylate transporter 4 (MCT4) knockout mice specifically tailored to the ICR strain, an optimal background for high-intensity exercise studies. A deficiency in MCT4 exacerbates the accumulation of lactate in skeletal muscle during high-intensity exercise. Pairing MCT4 deficiency with high-intensity interval training (HIIT) results in a synergistic boost in high-intensity exercise capacity, observable both at the organismal level (via a treadmill running test) and at the muscle tissue level (through an ex vivo muscle contractile function test). Coordinating MCT4 deficiency with HIIT enhances both the glycolytic enzyme activities and mitochondrial capacity to oxidize pyruvate.

Metabolomic response to acute resistance exercise in healthy older adults by 1H-NMR.

BACKGROUND: The favorable health-promoting adaptations to exercise result from cumulative responses to individual bouts of physical activity. Older adults often exhibit anabolic resistance; a phenomenon whereby the anabolic responses to exercise and nutrition are attenuated in skeletal muscle. The mechanisms contributing to age-related anabolic resistance are emerging, but our understanding of how chronological age influences responsiveness to exercise is incomplete. The objective was to determine the effects of healthy aging on peripheral blood metabolomic response to a single bout of resistance exercise and whether any metabolites in circulation are predictive of anabolic response in skeletal muscle. METHODS: Thirty young (20-35 years) and 49 older (65-85 years) men and women were studied in a cross-sectional manner. Participants completed a single bout of resistance exercise consisting of eight sets of 10 repetitions of unilateral knee extension at 70% of one-repetition maximum. Blood samples were collected before exercise, immediately post exercise, and 30-, 90-, and 180-minutes into recovery. Proton nuclear magnetic resonance spectroscopy was used to profile circulating metabolites at all timepoints. Serial muscle biopsies were collected for measuring muscle protein synthesis rates. RESULTS: Our analysis revealed that one bout of resistance exercise elicits significant changes in 26 of 33 measured plasma metabolites, reflecting alterations in several biological processes. Furthermore, 12 metabolites demonstrated significant interactions between exercise and age, including organic acids, amino acids, ketones, and keto-acids, which exhibited distinct responses to exercise in young and older adults. Pre-exercise histidine and sarcosine were negatively associated with muscle protein synthesis, as was the pre/post-exercise fold change in plasma histidine. CONCLUSIONS: This study demonstrates that while many exercise-responsive metabolites change similarly in young and older adults, several demonstrate age-dependent changes even in the absence of evidence of sarcopenia or frailty. TRIAL REGISTRATION: Clinical trial registry: ClinicalTrials.gov NCT03350906.

fhl2b mediates extraocular muscle protection in zebrafish models of muscular dystrophies and its ectopic expression ameliorates affected body muscles.

In muscular dystrophies, muscle fibers loose integrity and die, causing significant suffering and premature death. Strikingly, the extraocular muscles (EOMs) are spared, functioning well despite the disease progression. Although EOMs have been shown to differ from body musculature, the mechanisms underlying this inherent resistance to muscle dystrophies remain unknown. Here, we demonstrate important differences in gene expression as a response to muscle dystrophies between the EOMs and trunk muscles in zebrafish via transcriptomic profiling. We show that the LIM-protein Fhl2 is increased in response to the knockout of desmin, plectin and obscurin, cytoskeletal proteins whose knockout causes different muscle dystrophies, and contributes to disease protection of the EOMs. Moreover, we show that ectopic expression of fhl2b can partially rescue the muscle phenotype in the zebrafish Duchenne muscular dystrophy model sapje, significantly improving their survival. Therefore, Fhl2 is a protective agent and a candidate target gene for therapy of muscular dystrophies.

Effect of an immune challenge and two feed supplements on broiler chicken individual breast muscle protein synthesis rate.

Optimization of broiler chicken breast muscle protein accretion is key for the efficient production of poultry meat, whose demand is steadily increasing. In a context where antimicrobial growth promoters use is being restricted, it is important to find alternatives as well as to characterize the effect of immunological stress on broiler chicken's growth. Despite its importance, research on broiler chicken muscle protein dynamics has mostly been limited to the study of mixed protein turnover. The present study aims to characterize the effect of a bacterial challenge and the feed supplementation of citrus and cucumber extracts on broiler chicken individual breast muscle proteins fractional synthesis rates (FSR) using a recently developed dynamic proteomics pipeline. Twenty-one day-old broiler chickens were administered a single 2H2O dose before being culled at different timepoints. A total of 60 breast muscle protein extracts from five experimental groups (Unchallenged, Challenged, Control Diet, Diet 1 and Diet 2) were analysed using a DDA proteomics approach. Proteomics data was filtered in order to reliably calculate multiple proteins FSR making use of a newly developed bioinformatics pipeline. Broiler breast muscle proteins FSR uniformly decreased following a bacterial challenge, this change was judged significant for 15 individual proteins, the two major functional clusters identified as well as for mixed breast muscle protein. Citrus or cucumber extract feed supplementation did not show any effect on the breast muscle protein FSR of immunologically challenged broilers. The present study has identified potential predictive markers of breast muscle growth and provided new information on broiler chicken breast muscle protein synthesis which could be essential for improving the efficiency of broiler chicken meat production. SIGNIFICANCE: The present study constitutes the first dynamic proteomics study conducted in a farm animal species which has characterized FSR in a large number of proteins, establishing a precedent for biomarker discovery and assessment of health and growth status. Moreover, it has been evidenced that the decrease in broiler chicken breast muscle protein following an immune challenge is a coordinated event which seems to be the main cause of the decreased growth observed in these animals.

Skeletal Muscle Electrical Stimulation Prevents Progression of Disuse Muscle Atrophy via Forkhead Box O Dynamics Mediated by Phosphorylated Protein Kinase B and Peroxisome Proliferator-Activated Receptor gamma Coactivator-1alpha.

Although electrical muscle stimulation (EMS) of skeletal muscle effectively prevents muscle atrophy, its effect on the breakdown of muscle component proteins is unknown. In this study, we investigated the biological mechanisms by which EMS-induced muscle contraction inhibits disuse muscle atrophy progression. Experimental animals were divided into a control group and three experimental groups: immobilized (Im; immobilization treatment), low-frequency (LF; immobilization treatment and low-frequency muscle contraction exercise), and high-frequency (HF; immobilization treatment and high-frequency muscle contraction exercise). Following the experimental period, bilateral soleus muscles were collected and analyzed. Atrogin-1 and Muscle RING finger 1 (MuRF-1) mRNA expression levels were significantly higher for the experimental groups than for the control group but were significantly lower for the HF group than for the Im group. Peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) mRNA and protein expression levels in the HF group were significantly higher than those in the Im group, with no significant differences compared to the Con group. Both the Forkhead box O (FoxO)/phosphorylated FoxO and protein kinase B (AKT)/phosphorylated AKT ratios were significantly lower for the Im group than for the control group and significantly higher for the HF group than for the Im group. These results, the suppression of atrogin-1 and MuRF-1 expression for the HF group may be due to decreased nuclear expression of FoxO by AKT phosphorylation and suppression of FoxO transcriptional activity by PGC-1alpha. Furthermore, the number of muscle contractions might be important for effective EMS.

Increased extracellular matrix stiffness regulates myofibroblast transformation through induction of autophagy-mediated Kindlin-2 cytoplasmic translocation.

The extracellular matrix (ECM) mechanical properties regulate biological processes, such as fibroblast-myofibroblast transformation (FMT), which is a crucial component in pelvic organ prolapse (POP) development. The 'Kindlin-2' protein, expressed by fibroblasts, plays an important role in the development of the mesoderm, which is responsible for connective tissue formation; however, the role of Kindlin-2 in FMT remains to be explored. In this study, we aimed to explore the role of Kindlin-2 in FMT as it relates to POP. We found that ECM stiffness induces autophagy to translocate Kindlin-2 to the cytoplasm of L929 cells, where it interacts with and degrades MOB1, thereby facilitating Yes-associated protein (YAP) entry into the nucleus and influencing FMT progression. Stiffness-induced autophagy was inhibited when using an autophagy inhibitor, which blocked the translocation of Kindlin-2 to the cytoplasm and partially reversed high-stiffness-induced FMT. In patients with POP, we observed an increase in cytoplasmic Kindlin-2 and nuclear YAP levels. Similar changes in vaginal wall-associated proteins were observed in a mouse model of acute vaginal injury. In conclusion, Kindlin-2 is a key gene affecting ECM stiffness, which regulates FMT by inducing autophagy and may influence the development of POP.

The muscle protein synthetic response following corn protein ingestion does not differ from milk protein in healthy, young adults.

Plant-derived proteins are generally believed to possess lesser anabolic properties when compared with animal-derived proteins. This is, at least partly, attributed to the lower leucine content of most plant-derived proteins. Corn protein has a leucine content that is highest among most plant-derived proteins and it even exceeds the levels observed in animal-derived proteins such as whey protein. Therefore, this study aimed to compare muscle protein synthesis rates following the ingestion of 30 g corn protein and a 30 g blend of corn plus milk protein with 30 g milk protein. In a randomized, double blind, parallel-group design, 36 healthy young males (26 ± 4 y) received primed continuous L-[ring-13C6]-phenylalanine infusions and ingested 30 g corn protein (CORN), 30 g milk protein (MILK), or a 30 g proteinblend with 15 g corn plus 15 g milk protein (CORN + MILK). Blood and muscle biopsies were collected for 5 h following protein ingestion to assess post-prandial plasma amino acid profiles and myofibrillar protein synthesis rates. The results show that Ingestion of protein increased myofibrillar protein synthesis rates from basal post-absorptive values in all treatments(P < 0.001). Post-prandial myofibrillar protein synthesis rates did not differ between CORN vs MILK (0.053 ± 0.013 vs 0.053 ± 0.013%∙h-1, respectively; t-test P = 0.90), or between CORN + MILK vs MILK (0.052 ± 0.024 vs 0.053 ± 0.013%∙h-1, respectively; t-test P = 0.92). Ingestion of 30 g corn protein, 30 g milk protein, or a blend of 15 g corn plus 15 g milk protein robustly increases muscle protein synthesis rates in young males. The muscle protein synthetic response to the ingestion of 30 g corn-derived protein does not differ from the ingestion of an equivalent amount of milk protein in healthy, young males. Clinical Trial Registry number. NTR6548 (registration date: 27-06-2017) https://www.trialregister.nl/ .

ROS in diabetic atria regulate SK2 degradation by Atrogin-1 through the NF-κB signaling pathway.

One of the independent risk factors for atrial fibrillation is diabetes mellitus (DM); however, the underlying mechanisms causing atrial fibrillation in DM are unknown. The underlying mechanism of Atrogin-1-mediated SK2 degradation and associated signaling pathways are unclear. The aim of this study was to elucidate the relationship among reactive oxygen species (ROS), the NF-κB signaling pathway, and Atrogin-1 protein expression in the atrial myocardia of DM mice. We found that SK2 expression was downregulated comitant with increased ROS generation and enhanced NF-κB signaling activation in the atrial cardiomyocytes of DM mice. These observations were mimicked by exogenously applicating H2O2 and by high glucose culture conditions in HL-1 cells. Inhibition of ROS production by diphenyleneiodonium chloride or silencing of NF-κB by siRNA decreased the protein expression of NF-κB and Atrogin-1 and increased that of SK2 in HL-1 cells with high glucose culture. Moreover, chromatin immunoprecipitation assay demonstrated that NF-κB/p65 directly binds to the promoter of the FBXO32 gene (encoding Atrogin-1), regulating the FBXO32 transcription. Finally, we evaluated the therapeutic effects of curcumin, known as a NF-κB inhibitor, on Atrogin-1 and SK2 expression in DM mice and confirmed that oral administration of curcumin for 4 weeks significantly suppressed Atrogin-1 expression and protected SK2 expression against hyperglycemia. In summary, the results from this study indicated that the ROS/NF-κB signaling pathway participates in Atrogin-1-mediated SK2 regulation in the atria of streptozotocin-induced DM mice.

FHL2 promotes the aggressiveness of lung adenocarcinoma by inhibiting autophagy via activation of the PI3K/AKT/mTOR pathway.

BACKGROUND: Increasing evidence indicates that four and a half LIM domains 2 (FHL2) plays a crucial role in the progression of various cancers. However, the biological functions and molecular mechanism of FHL2 in lung adenocarcinoma (LUAD) remain unclear. METHODS: We evaluated the prognostic value of FHL2 in LUAD using public datasets and further confirmed its prognostic value with our clinical data. The biological functions of FHL2 in LUAD were evaluated by in vitro and in vivo experiments. Pathway analysis and rescue experiments were subsequently performed to explore the molecular mechanism by which FHL2 promoted the progression of LUAD. RESULTS: FHL2 was upregulated in LUAD tissues compared to adjacent normal lung tissues, and FHL2 overexpression was correlated with unfavorable outcomes in patients with LUAD. FHL2 knockdown significantly suppressed the proliferation, migration and invasion of LUAD cells, while FHL2 overexpression had the opposite effect. Mechanistically, FHL2 upregulated the PI3K/AKT/mTOR pathway and subsequently inhibited autophagy in LUAD cells. The effects FHL2 on the proliferation, migration and invasion of LUAD cells are dependent on the inhibition of autophagy, as of induction autophagy attenuated the aggressive phenotype induced by FHL2 overexpression. CONCLUSIONS: FHL2 promotes the progression of LUAD by activating the PI3K/AKT/mTOR pathway and subsequently inhibiting autophagy, which can be exploited as a potential therapeutic target for LUAD.

Myomerger Induces Membrane Hemifusion and Regulates Fusion Pore Expansion.

Membrane fusion is a crucial mechanism in a wide variety of important events in cell biology from viral infection to exocytosis. However, despite many efforts and much progress, cell-cell fusion has remained elusive to our understanding. Along the life of the fusion pore, large conformational changes take place from the initial lipid bilayer bending, passing through the hemifusion intermediates, and ending with the formation of the first nascent fusion pore. In this sense, computer simulations are an ideal technique for describing such complex lipid remodeling at the molecular level. In this work, we studied the role played by the muscle-specific membrane protein Myomerger during the formation of the fusion pore. We have conducted µs length atomistic and coarse-grained molecular dynamics, together with free-energy calculations using ad hoc collective variables. Our results show that Myomerger favors the hemifusion diaphragm-stalk transition, reduces the nucleation-expansion energy difference, and promotes the formation of nonenlarging fusion pores.

Plasminogen deficiency exacerbates skeletal muscle loss during mechanical unloading in developing mice.

Mechanical-unloading-induced skeletal muscle atrophy results in physical frailty and disability. Elucidating its mechanism is required to establish effective countermeasures for this muscle adaptation. First, we analyzed the proteome profile in the gastrocnemius (Gast) and soleus muscles of space-flown mice raised under microgravity or artificial 1-g for 30 days, and found that the expression levels of fibrinolysis-related proteins were significantly elevated in the mechanical-unloaded muscles. Next, we investigated the roles of the fibrinolytic system in skeletal muscle atrophy induced by mechanical unloading on the ground. Eight-week-old male mice with plasminogen gene deficiency (Plg-/-) and their wild-type littermates were divided into control and hindlimb-suspended groups and were raised for 21 days. Plasminogen deficiency significantly enhanced the decrease in muscle mass at the lower limbs of mice following hindlimb unloading, and the Gast muscle atrophy was more prominent in Plg-/- mice. In addition, plasminogen deficiency significantly increased the expression of autophagy-related markers, beclin1 mRNA and LC3B protein, in the mechanical-unloaded Gast muscles, but did not affect the increase in the gene expression of ubiquitin ligases, atrogin-1 and MuRF1. Neither plasminogen deficiency nor hindlimb unloading affected the Akt/mechanistic target of rapamycin pathway in the Gast muscles. These results suggested that plasminogen deficiency might accelerate protein breakdown via the autophagy-lysosome, but not the ubiquitin-proteasome, system in the mechanical-unloaded Gast muscles. In conclusion, we first showed that plasminogen deficiency exacerbated the Gast muscle atrophy in hindlimb-unloaded mice. Plasminogen and the fibrinolysis system might play some protective roles against muscle atrophy induced by mechanical unloading in developing mice.NEW & NOTEWORTHY The expression levels of fibrinolysis-related proteins, including plasminogen, were significantly elevated in the gastrocnemius (Gast) and soleus muscles of mice following 30-day microgravity exposure. Plasminogen deficiency exacerbated atrophy of the Gast, but not the soleus, muscles in mice following 21-day hindlimb suspension. It was also suggested that protein breakdown via the autophagy-lysosome system was accelerated in the Gast muscles. Plasminogen might play some protective roles against muscle atrophy induced by mechanical unloading in developing mice.

ANKRD1 is a mesenchymal-specific driver of cancer-associated fibroblast activation bridging androgen receptor loss to AP-1 activation.

There are significant commonalities among several pathologies involving fibroblasts, ranging from auto-immune diseases to fibrosis and cancer. Early steps in cancer development and progression are closely linked to fibroblast senescence and transformation into tumor-promoting cancer-associated fibroblasts (CAFs), suppressed by the androgen receptor (AR). Here, we identify ANKRD1 as a mesenchymal-specific transcriptional coregulator under direct AR negative control in human dermal fibroblasts (HDFs) and a key driver of CAF conversion, independent of cellular senescence. ANKRD1 expression in CAFs is associated with poor survival in HNSCC, lung, and cervical SCC patients, and controls a specific gene expression program of myofibroblast CAFs (my-CAFs). ANKRD1 binds to the regulatory region of my-CAF effector genes in concert with AP-1 transcription factors, and promotes c-JUN and FOS association. Targeting ANKRD1 disrupts AP-1 complex formation, reverses CAF activation, and blocks the pro-tumorigenic properties of CAFs in an orthotopic skin cancer model. ANKRD1 thus represents a target for fibroblast-directed therapy in cancer and potentially beyond.

Lower basal and postprandial muscle protein synthesis after 2 weeks single-leg immobilization in older men: No protective effect of anti-inflammatory medication.

Muscle inactivity may reduce basal and postprandial muscle protein synthesis (MPS) rates in humans. Anti-inflammatory treatment alleviates the MPS impairments in younger individuals. The present study explored the influence of nonsteroidal anti-inflammatory drugs (NSAIDs) upon MPS during a period of inactivity in older humans. Eighteen men (age 60-80 years) were allocated to ibuprofen (1200 mg/day, Ibu) or control (Plc) groups. One lower limb was cast immobilized for 2 weeks. Postabsorptive and postprandial MPS was measured before and after the immobilization by L-[ring-13 C6 ]-phenylalanine infusion. The protein expression of select anabolic signaling molecules was investigated by western blot. Basal (0.038 ± 0.002%/h and 0.039 ± 0.005%/h, Plc and Ibu, respectively) and postprandial (0.064 ± 0.004%/h and 0.067 ± 0.010%/h, Plc and Ibu, respectively) MPS rate were higher pre-immobilization compared to basal (0.019 ± 0.005%/h and 0.020 ± 0.010%/h, Plc and Ibu, respectively) and postprandial (0.033 ± 0.005%/h and 0.037 ± 0.006%/h, Plc and Ibu, respectively) MPS rate post-immobilization (p < 0.001). NSAID treatment did not affect the suppression of MPS (p > 0.05). The anabolic signaling were in general reduced after immobilization (p < 0.05). These changes were unaffected by NSAID treatment (p > 0.05). Basal and postprandial MPS dropped markedly after 2 weeks of lower limb immobilization. NSAID treatment neither influenced the reduction in MPS nor the anabolic signaling after immobilization in healthy older individuals.