Isolation of mitochondria from cells and tissues

Isolated mitochondria are useful to study fundamental processes including mitochondrial respiration, metabolic activity, protein import, membrane fusion, protein complex assembly, as well as interactions of mitochondria with the cytoskeleton, nuclear encoded mRNAs, and other organelles. In addition, studies of the mitochondrial proteome, phosphoproteome, and lipidome are dependent on preparation of highly purified mitochondria (Boldogh, Vojtov, Karmon, & Pon, 1998; Cui, Conte, Fox, Zara, & Winge, 2014; Marc et al., 2002; Meeusen, McCaffery, & Nunnari, 2004; Reinders et al., 2007; Schneiter et al., 1999; Stuart & Koehler, 2007). Most methods to isolate mitochondria rely on differential centrifugation, a two-step centrifugation carried out at low speed to remove intact cells, cell and tissue debris, and nuclei from whole cell extracts followed by high speed centrifugation to concentrate mitochondria and separate them from other organelles. However, methods to disrupt cells and tissue vary. Moreover, density gradient centrifugation or affinity purification of the organelle are used to further purify mitochondria or to separate different populations of the organelle. Here, we describe protocols to isolate mitochondria from different cells and tissues as well as approaches to assess the purity and integrity of isolated organelles.