Nuclear and nuclear envelope localization of dystrophin Dp71 and dystrophin‐associated proteins (DAPs) in the C₂C₁₂ muscle cells: DAPs nuclear localization is modulated during myogenesis

Abstract

Dystrophin and dystrophin-associated proteins (DAPs) form a complex around the sarcolemma, which gives stability to the sarcolemma and leads signal transduction. Recently, the nuclear presence of dystrophin Dp71 and DAPs has been revealed in different non-muscle cell types, opening the possibility that these proteins could also be present in the nucleus of muscle cells. In this study, we analyzed by Immunofluorescence assays and Immunoblotting analysis of cell fractions the subcellular localization of Dp71 and DAPs in the C(2)C(12) muscle cell line. We demonstrated the presence of Dp71, alpha-sarcoglycan, alpha-dystrobrevin, beta-dystroglycan and alpha-syntrophin not only in plasma membrane but also in the nucleus of muscle cells. In addition, we found by Immunoprecipitation assays that these proteins form a nuclear complex. Interestingly, myogenesis modulates the presence and/or relative abundance of DAPs in the plasma membrane and nucleus as well as the composition of the nuclear complex. Finally, we demonstrated the presence of Dp71, alpha-sarcoglycan, beta-dystroglycan, alpha-dystrobrevin and alpha-syntrophin in the C(2)C(12) nuclear envelope fraction. Interestingly, alpha-sarcoglycan and beta-dystroglycan proteins showed enrichment in the nuclear envelope, compared with the nuclear fraction, suggesting that they could function as inner nuclear membrane proteins underlying the secondary association of Dp71 and the remaining DAPs to the nuclear envelope. Nuclear envelope localization of Dp71 and DAPs might be involved in the nuclear envelope-associated functions, such as nuclear structure and modulation of nuclear processes.

Nuclear Recruitment of Neuronal Nitric-oxide Synthase by α-Syntrophin Is Crucial for the Induction of Mitochondrial Biogenesis

“…Similarly, treatments with NO donors favor mitochondrial biogenesis and myogenesis and restore oxidative capacity in affected myocytes (71, 72). In conclusion, our results show that nNOS is anchored via the PDZ domain also at the Dystrophin-Syntrophin complex sited at the nuclear envelope of myocytes (58), and this event is mandatory for the NO/CREB/PGC-1␣-driven mitochondrial biogenesis. On the basis of our results, it is conceivable that the lack of nNOS anchoring to the nucleus may contribute to myopathy because of impaired mitochondrial biogenesis.…”

“…However, ␣-Syntrophin and Dystrophin have been also observed in the inner nuclear membrane of cultured myocytes, and its level increases during myogenesis in nuclei (57,58). Interestingly, nNOS␣ has been revealed in the nuclear membrane of HeLa cells in association with Dystrophin and ␣-Syntrophin (46).…”

Dystrophin Dp71 is Critical for Stability of the DAPs in the Nucleus of PC12 Cells

“…The nuclear DAPC is not cell-type specific, we have characterized similar complexes in the nucleus of HeLa [26] and C2C12 cells [27], which suggests an important unknown role for this complex in nuclear activities. We found that Dp71d as well as b-dystroglycan and b-dystrobrevin are associated with the nuclear matrix, a permanent network of core filaments underlying ticker fibers which is proposed to be the platform for numerous nuclear processes, including RNA processing, transcription regulation and DNA repair.…”

“…The presence of Dp71d and the dystrophin-associated proteins (DAPs) has been observed in the nuclei of HeLa and C2C12 cells [26,27]. Therefore, we decided to ascertain whether these proteins display nuclear localization in the PC12 neuronal cells.…”

Dystrophin–Glycoprotein Complex in Blood Cells

“…The presence of Dp71 and some DGC elements that form a nuclear complex at the plasma membrane and in the nucleus of muscle cells suggested their participation in nuclear structure and in the modulation of nuclear processes [42].…”