Biology subjects

Hitachi, K.

Publications and source records attributed to Hitachi, K..

4 recordsLinked to original sources

bioRxiv2026

Repeated intermittent clenbuterol administration induces exposure history-dependent proteomic remodeling in mouse skeletal muscle

Clenbuterol (CB), a {beta}2-adrenergic receptor agonist, is known to increase skeletal muscle mass. However, because its effects are influenced by treatment duration, dose, and {beta}-adrenergic receptor responsiveness, it remains unclear how extended intermittent CB exposure alters the skeletal muscle proteome. In this study, we established a repeated intermittent CB administration model in mice and compared the effects of single and repeated CB exposure on plantaris muscle using label-free quantitative proteomics. Repeated CB exposure produced a more evident muscle-weight response than single exposure under the same long-term experimental timeline. Proteomic profiling revealed that repeated CB exposure was not a simple reproduction or amplification of the single CB response, but was associated with distinct changes in sarcomere-associated, tissue-remodeling-related, membrane-trafficking-related, and metabolic proteins. Integrated response-class analysis further identified multiple patterns of protein regulation, including shared CB-responsive proteins and proteins preferentially identified as changed under repeated CB conditions. Immunoblotting validated representative proteins from these response classes: Klhl40 and Napa as shared CB-responsive proteins, Galectin-3 as a strongly CB-responsive remodeling-related protein, and Rab18 as a protein change more clearly detected under repeated CB conditions. Together, these findings indicate that repeated intermittent CB exposure induces exposure history-dependent proteomic remodeling in skeletal muscle. This study provides a resource for understanding the molecular consequences of repeated CB exposure and for future mechanistic studies of {beta}2-adrenergic stimulation-induced skeletal muscle adaptation.

molecular biology↗

bioRxiv2026

Cardiac-Detargeted MyoAAV Enables Systemic Nrl-Mediated Fast Myofiber Remodeling and Hypertrophy Across Multiple Skeletal Muscles

Inducing fast myofiber programs offers therapeutic potential for skeletal muscle disorders such as sarcopenia, where fast myofibers are preferentially lost. Engineered muscle-specific AAV (MyoAAV) vectors enable efficient transduction of skeletal muscles after systemic administration; however, cardiac transgene expression limits applications requiring skeletal muscle-selective delivery. We generated modified MyoAAV vectors by incorporating cardiac-specific miR-208a target sequences into the transgene 3'UTR. This design markedly suppressed cardiac expression while preserving skeletal muscle output, with target-site variation enabling tunable trade-offs between cardiac detargeting and skeletal muscle expression levels. We validated this platform using neural retina leucine zipper (Nrl), a large Maf transcription factor regulating type IIb myofiber identity. Systemic delivery of conventional MyoAAV-Nrl caused severe cardiac hypertrophy and uniform lethality within one month. Conversely, incorporating miR-208a target sequences prevented detectable hypertrophy and eliminated mortality during the experimental observation period. This modification significantly reduced cardiac Nrl expression while maintaining skeletal muscle levels, successfully promoting type IIb myofiber formation and hypertrophy across multiple skeletal muscles. These findings demonstrate that miR-208a-mediated cardiac detargeting combined with MyoAAV-Nrl enables safe systemic induction of fast myofiber remodeling and hypertrophy, establishing a platform for gene therapies targeting skeletal muscle disorders associated with fast myofiber loss.

cell biology↗

bioRxiv2023

Protective effects of Mkl1/2 against lipodystrophy and muscle atrophy via PI3K/AKT-independent FoxO repression

FoxO transcription factors are involved in the pathogenesis of lipodystrophy and muscle atrophy. FoxO proteins are phosphorylated and inactivated by PI3K/AKT signaling; however, little is known about FoxO repressors other than this pathway. Our study showed that the Srf cofactors Mkl1 and Mkl2 directly repressed FoxO transcriptional activity, independent of the PI3K/AKT pathway. Loss of Mkl1/2 led to the overactivation of FoxO, which impaired the maintenance of both white adipose tissue (WAT) and skeletal muscle. In Mkl2-deficient preadipocytes, Ppar{gamma} was suppressed and white adipogenesis was severely impaired. In myotubes, Mkl1 and Mkl2 suppressed the expression of atrophy-related genes (atrogenes) induced by FoxO. Mkl1 expression was reduced at the onset of muscle atrophy in vivo, and exogenous supplementation of skeletal muscle Mkl1 suppressed atrogene expression and induced muscle hypertrophy. Finally, both Mkl2 nuclear localization and Mkl1/2 expression were upregulated by exercise, suggesting that Mkl1/2 is involved in the inhibitory effect of exercise on muscle atrophy. These findings indicate that Mkl1/2 act as PI3K/AKT signaling-independent repressors of FoxO and are essential for adipose and muscle tissue homeostasis.

cell biology↗

bioRxiv2021

Multiple roles of heterogeneous nuclear ribonucleoprotein K during skeletal muscle cell differentiation

RNA-binding proteins (RBPs) regulate cell physiology via the formation of ribonucleic-protein complexes with coding and non-coding RNAs. RBPs have multiple functions in the same cells; however, the precise mechanism through which their pleiotropic functions are determined remains unknown. In this study, we revealed the multiple inhibitory functions of heterogeneous nuclear ribonucleoprotein K (hnRNPK) for myogenic differentiation. We first identified hnRNPK as a lncRNA Myoparr binding protein. Gain- and loss-of-function experiments showed that hnRNPK repressed the expression of myogenin at the transcriptional level. The hnRNPK-binding region of Myoparr was required to repress myogenin expression. Moreover, hnRNPK repressed the expression of a set of genes coding for aminoacyl-tRNA synthetases in a Myoparr-independent manner. Mechanistically, hnRNPK regulated the eIF2/Atf4 pathway, one branch of the intrinsic pathways of the endoplasmic reticulum sensors, in differentiating myoblasts. Thus, our findings demonstrate that hnRNPK plays lncRNA-associated and - independent multiple roles during myogenic differentiation, indicating that the analysis of lncRNA-binding proteins will be useful for elucidating both the physiological functions of lncRNAs and the multiple functions of RBPs.

cell biology↗