Figure 4. PEX11β and peroxisomal membrane interactions with mitochondria.

(a-m) COS-7 cells were transfected with PEX11β-EGFP, mitochondria were stained with Mitotracker (red) and cells observed live using a spinning disc microscope. PEX11β, a membrane shaping protein, induces the formation of tubular membrane protrusions from globular peroxisomes. We show here that those membrane protrusions can interact with mitochondria. Results are representative of three independent experiments. (a-f) shows a peroxisome which interacts with a mitochondrion via its membrane protrusion (arrowhead), and follows it, occasionally detaching and re-establishing contact before interacting with another mitochondrion (see Supplementary Movie 1). (g-m) shows a mitochondrion (arrowhead) which interacts with a peroxisome via a peroxisomal membrane protrusion. It then detaches and moves away to interact with another peroxisome, which wraps its protrusion around it, before interacting with another mitochondrion (see Supplementary Movie 2). (n) Quantification of interactions between spherical or elongated peroxisomes (PO) with mitochondria (MITO). The average result of 3 independent experiments is shown, error bars indicate the mean +/- standard deviation. (o) Quantification of contact time. Note that elongated PO interact more frequently with MITO than spherical PO, but for similar time periods. PO-MITO interactions are generally long-lasting (see Supplementary Movie 3) (n=200 peroxisomes from 5 different cells). Dotted line indicates the mean, error bars indicate standard deviation. *** P = 0.0003 from a two-tailed unpaired t test; Time (min:sec). Scale bars, 5 µm.