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+.
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 Ca2+-sensitive. In the present study, we analyzed the effects of the Ca2+ 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 Ca2+ 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.
Mermelstein
C S
CS
Departamento de Histologia e Embriologia, Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, RJ, Brasil. mermelstein@ufrj.br
Amaral
L M
LM
Rebello
M I L
MI
Reis
J S N
JS
Borojevic
R
R
Costa
M L
ML
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D048430:Cell Shape / Q000502:physiology*; D002614:Chelating Agents / Q000494:pharmacology; D003893:Desmin / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D004533:Egtazic Acid / Q000494:pharmacology; D005109:Extracellular Matrix; D007382:Intermediate Filaments / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008856:Microscopy, Fluorescence; D018482:Muscle, Skeletal / Q000737:chemistry*; D032446:Myoblasts / Q000502:physiology*; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction
D002614:Chelating Agents; D003893:Desmin; D004533:Egtazic Acid; D002118:Calcium