Aggregate-prone desmin mutations impair mitochondrial calcium uptake in primary myotubes

• Transduced satellite cells fuse into twitching myotubes expressing gene of interest.
• Evoked SR calcium release results in mitochondrial calcium ([Ca2+]mit) uptake.
• Aggregate-prone desmin mutations decrease [Ca2+]mit in comparison to WT.
• Non-aggregate-prone desmin mutations do not decrease [Ca2+]mit in comparison to WT.
• Aggregate-prone desmin mutations result in elevated resting cytosolic [Ca2+].

Desmin, being a major intermediate filament of mature muscle cell, interacts with mitochondria within the cell and participates in mitochondria proper localization. The goal of the present study was to assess the effect of aggregate-prone and non-aggregate-prone desmin mutations on mitochondrial calcium uptake. Primary murine satellite cells were transduced with lentiviruses carrying desmin in wild type or mutant form, and were induced to differentiate into myotubes. Four mutations resulting in different degree of desmin aggregates formation were analyzed. Tail domain mutation Asp399Tyr has the mildest impact on desmin filament polymerization, rod domain mutation Ala357Pro causes formation of large aggregates composed of filamentous material, and Leu345Pro and Leu370Pro are considered to be the most severest in their impact on desmin polymerization and structure. For mitochondrial calcium measurement cells were loaded with rhod 2-AM. We found that aggregate-prone mutations significantly decreased [Ca2+]mit, whereas non-aggregate-prone mutations did not decrease [Ca2+]mit. Moreover aggregate-prone desmin mutations resulted in increased resting cytosolic [Ca2+]. However this increase was not accompanied by any alterations in sarcoplasmic reticulum calcium release. We suggest that the observed decline in [Ca2+]mit was due to desmin aggregate accumulation resulting in the loss of desmin mitochondria interactions.

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