Figure 4.

APOL1 transport to mitochondrial matrix is required for formation of higher-order oligomers. (A and B) Knockdown of TIMM17 (a key component of the IMM protein translocation machinery) or HSPA9 (a mitochondrial matrix translocation chaperone needed to guide proteins through the translocation machinery) prevents APOL1 higher-order oligomer formation (in addition to preventing cell death: see Figure 2D). Conversely, knockdown of TIMM22 affects neither cell death nor APOL1 oligomer formation (see Supplemental Figure 6C). Stable APOL1-transfected cells were treated for 48 hours with siRNA prior to inducing APOL1 with 50 ng/ml tetracycline. Cells were lysed with digitonin after 15 hours and were fractionated by native PAGE (large top panels) or SDS page (lower narrow panels). The signal from the monomeric fraction is saturated in these images.