SUMO1 and sarcopenia: For instance, if aging muscle upregulates SENP5 (as seen in failing heart), DRP1 would lose SUMO1 and fission could decline, resulting in enlarged, dysfunctional mitochondria.41 Conversely, failure to deSUMOylate DRP1 (or a shift toward SUMO1 dominance) might over-activate fission and mitophagy.41 Such an age-dependent drift in the SUMO1/SUMO2 balance would be expected to affect both mitochondrial turnover and network architecture during Sarcopenia.