Background: Nuclear receptor interaction protein (NRIP) is versatile and engages with various proteins to execute its diverse biological function. NRIP deficiency was reported to cause small myofibre size in adult muscle regeneration, indicating a crucial role of NRIP in myoblast fusion.
Methods: The colocalization and interaction of NRIP with actin were investigated by immunofluorescence and immunoprecipitation assay, respectively. The participation of NRIP in myoblast fusion was demonstrated by cell fusion assay and time-lapse microscopy. The NRIP mutants were generated for mechanism study in NRIP-null C2C12 (termed KO19) cells and muscle-specific NRIP knockout (NRIP cKO) mice. A GEO profile database was used to analyse NRIP expression in Duchenne muscular dystrophy (DMD) patients.
Results: In this study, we found that NRIP directly and reciprocally interacted with actin both in vitro and in cells. Immunofluorescence microscopy showed that the endogenous NRIP colocalized with components of invadosome, such as actin, Tks5, and cortactin, at the tips of cells during C2C12 differentiation. The KO19 cells were generated and exhibited a significant deficit in myoblast fusion compared with wild-type C2C12 cells (3.16% vs. 33.67%, p < 0.005). Overexpressed NRIP in KO19 cells could rescue myotube formation compared with control (3.37% vs. 1.00%, p < 0.01). We further confirmed that NRIP directly participated in cell fusion by using a cell-cell fusion assay. We investigated the mechanism of invadosome formation for myoblast fusion, which depends on NRIP-actin interaction, by analysing NRIP mutants in NRIP-null cells. Loss of actin-binding of NRIP reduced invadosome (enrichment ratio, 1.00 vs. 2.54, p < 0.01) and myotube formation (21.82% vs. 35.71%, p < 0.05) in KO19 cells and forced NRIP expression in KO19 cells and muscle-specific NRIP knockout (NRIP cKO) mice increased myofibre size compared with controls (over 1500 μm, 61.01% vs. 20.57%, p < 0.001). We also found that the NRIP mRNA level was decreased in DMD patients compared with healthy controls (18 072 vs. 28 289, p < 0.001, N = 10 for both groups).
Conclusions: NRIP is a novel actin-binding protein for invadosome formation to induce myoblast fusion.
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http://dx.doi.org/10.1002/jcsm.13598 | DOI Listing |
Cells
December 2024
Department of Physiology, College of Medicine, The Catholic University of Korea, Seoul 06591, Republic of Korea.
Injured or atrophied adult skeletal muscles are regenerated through terminal differentiation of satellite cells to form multinucleated muscle fibers. Transplantation of satellite cells or cultured myoblasts has been used to improve skeletal muscle regeneration. Some of the limitations observed result from the limited number of available satellite cells that can be harvested and the efficiency of fusion of cultured myoblasts with mature muscle fibers (i.
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View Article and Find Full Text PDFbioRxiv
December 2024
Department of Bioengineering, University of California, Berkeley, CA 94720.
Cell-cell fusion is fundamental to developmental processes such as muscle formation, as well as to viral infections that cause pathological syncytia. An essential step in fusion is close membrane apposition, but cell membranes are crowded with proteins, glycoproteins, and glycolipids, all of which must be cleared before a fusion pore can be nucleated. Here, we find that cell surface crowding drastically reduces fusogenicity in multiple systems, independent of the method for driving fusion.
View Article and Find Full Text PDFElife
December 2024
Translational Cardiology and Functional Genomics, Max Delbrück Center for Molecular Medicine, Berlin, Germany.
The giant striated muscle protein titin integrates into the developing sarcomere to form a stable myofilament system that is extended as myocytes fuse. The logistics underlying myofilament assembly and disassembly have started to emerge with the possibility to follow labeled sarcomere components. Here, we generated the mCherry knock-in at titin's Z-disk to study skeletal muscle development and remodeling.
View Article and Find Full Text PDFInt J Mol Sci
November 2024
Gansu Key Laboratory of Herbivorous Animal Biotechnology, Faculty of Animal Science and Technology, Gansu Agricultural University, Lanzhou 730070, China.
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