Drp1S616 phosphorylation inhibits oligomerization and mitochondrial translocation of Drp1. (a) Immunoblotting of monomeric (∼80 kDa), tetrameric (∼320 kDa) and the higher-ordered oligomeric forms of Drp1 and pDrp1S616 in cultured cortical neurons. SDS-PAGE with or without DTT was performed and followed by immunoblotting. Arrows and arrowheads indicate tetrameric or oligomeric Drp1 and monomeric Drp1, respectively. (b) Quantification of the ratio of pDrp1S616 versus total Drp1 in monomeric or oligomeric fractions. *P<0.05, n=3. (c) Immunoblot of Drp1 and pDrp1S616 in cytosolic or mitochondrial fractions. Immunoblots of GAPDH and HSP60 were used as loading controls of mitochondrial and cytosolic fractions, respectively. (d) Quantification of the ratio of pDrp1S616 versus total Drp1 in cytosolic or mitochondrial fractions. *P<0.05, n=3. (e) Immunoblot of monomeric, tetrameric and oligomeric forms of Drp1 and pDrp1S616 from cells treated with or without roscovitine (20 μM) for2 h. Arrows and arrowheads indicate tetrameric or oligomeric Drp1 and monomeric Drp1, respectively. (f) Quantification of the ratio of Drp1 in monomeric and oligomeric fractions from cells treated with or without roscovitine. *P<0.05, n=3. (g) Immunoblot of Drp1 and pDrp1S616 in cytosolic or mitochondrial fractions from cells treated with or without roscovitine (100 μM) for two hours. (h) Quantification of the ratio of Drp1 in cytosolic or mitochondrial fractions from cells treated with or without roscovitine. *P<0.05, n=3.