Changes in cell shape and desmin intermediate filament distribution are associated with down-regulation of desmin expression in C2C12 myoblasts grown in the absence of extracellular Ca2+

Abstract

Desmin is the main intermediate filament (IF) protein of muscle cells. In skeletal muscle, desmin IFs form a scaffold that interconnects the entire contractile apparatus with the subsarcolemmal cytoskeleton and cytoplasmic organelles. The interaction between desmin and the sarcolemma is mediated by a number of membrane proteins, many of which are Ca 2+ -sensitive. In the present study, we analyzed the effects of the Ca 2+ chelator EGTA (1.75 mM) on the expression and distribution of desmin in C2C12 myoblasts grown in culture. We used indirect immunofluorescence microscopy and reverse transcription polymerase chain reaction (RT-PCR) to analyze desmin distribution and expression in C2C12 cells grown in the presence or absence of EGTA. Control C2C12 myoblasts showed a well-spread morphology after a few hours in culture and became bipolar when grown for 24 h in the presence of EGTA. Control C2C12 cells showed a dense network of desmin from the perinuclear region to the cell periphery, whereas EGTA-treated cells showed desmin aggregates in the cytoplasm. RT-PCR analysis revealed a down-regulation of desmin expression in EGTA-treated C2C12 cells compared to untreated cells. The present results suggest that extracellular Ca 2+ availability plays a role in the regulation of desmin expression and in the spatial distribution of desmin IFs in myoblasts, and is involved in the generation and maintenance of myoblast cell shape.

Structural Analysis of Alterations in Zebrafish Muscle Differentiation Induced by Simvastatin and Their Recovery with Cholesterol

“…The knockdown of muscle-specific caveolin causes the disorganization of membrane microdomains and muscle dystrophy (Galbiati et al 2001). We have previously demonstrated that disorganization of lipid rafts by treatment with the cholesterol-sequestering drug methyl-beta-cyclodextrin leads to alterations in the structural and signaling aspects of myogenesis (Mermelstein et al 2005;Mermelstein et al 2007;Portilho et al 2012).…”

The In Vitro Cytotoxic Effects of Ionophore Exposure on Selected Cytoskeletal Proteins of C2C12 Myoblasts

“…Ultrastructural studies of skeletal muscles of animals affected following ionophore exposure reported myofibrillar degeneration and necrosis, with disrupted contractile apparatus [ 22 , 23 ]. The disruption in the desmin intermediate filament network observed in the current study could thus contribute to the myofibrillar degeneration previously reported, as desmin is primarily associated with the Z-disk of striated muscle [ 25 , 26 , 27 , 28 ].…”

“…After monensin and salinomycin exposure, the desmin intermediate filament aggregated perinuclearly ( Figure 4 ). Desmin is a critical component in the myofiber network, and various myopathies are associated with its disruption and aggregation [ 27 ]. Additionally, desmin plays a role in determining the intracellular location of mitochondria and regulating their respiratory function [ 29 , 30 ].…”

“…The sarcomere is the most basic contractile unit of a muscle, with actin (thin) and myosin (thick) filaments, working in tandem alongside various other proteins, adenosine triphosphate (ATP), and calcium to facilitate contraction. Desmin, a muscle-specific intermediate filament is found primarily at the Z-disk of the sarcomere and assists with maintaining muscle cytoarchitecture [ 25 , 26 , 27 , 28 ]. Additionally, desmin regulates the positioning of mitochondria within the cytoplasm, thus affecting their respiratory ability [ 29 , 30 ].…”

Histopathology of Skeletal Muscle in a Distal Motor Neuropathy Associated with a Mutant CCT5 Subunit: Clues for Future Developments to Improve Differential Diagnosis and Personalized Therapy

“…Almost no colocalization of CCT5 with desmin was observed in the extracellular matrix of affected tissue αB-crystallin signal was weaker than in healthy tissue αB-crystallin was present as light bands in longitudinal sections and as precipitates with desmin in the sarcoplasm Colocalization of αB-crystallin and desmin was reduced by half in affected muscle, compared with healthy muscle Hsp90 was present but appeared with an irregular pattern similar to that of desmin Hsp90 and desmin colocalization was reduced in the affected muscle, compared with healthy muscle and desmin, but it is known that desmin damage/disturbance/absence are closely related to morphological alterations of skeletal muscle fibers [18,19].…”