Peroxisome Partitioning

Upon cell division it is important that each eukaryotic progeny cell receives a set of the complete organel repertoire. An elaborate number of processes is required for proper nuclear division and partitioning. For a long time the notion was entertained that this was not required for most other organelles because their presence in large numbers sufficed that each daughter cell received its fair share on stochastic grounds. Recent work, particularly on partitioning of mitochondria during cell division, demonstrates that this is not the case and that also here precise partitioning involving many proteins is the rule.

Inspired by these new findings we have studied how peroxisomes partition during cell division. We have constructed a S. cerevisiae strain producing GFP-PTS1, which is incorporated into peroxisomes. The fluorescently-labeled peroxisomes were followed during cell multiplication using real-time imaging. We demonstrated that partitioning of peroxisomes during bud formation is a well-controlled process involving the actin cytoskeleton and the motor protein Myo2.

The individual behaviour of peroxisomes was particularly well visible in a mutant cell lacking one of the three dynamins present in yeast (∆vps1). In this mutant only a single peroxisome is left which partitions and segregates with equal precision and efficiency as the nucleus.

Hoepfner D, van den Berg M, Philippsen P, Tabak HF & Hettema EH A role for Vps1p, actin, and the Myo2p motor in peroxisome abundance and inheritance in Saccharomyces cerevisiae. J Cell Biol. 2001;155:979-90. pdf

After charting the partitioning process in rough outline we can now address more detailed questions: how does the Myo2 protein adhere to peroxisomes, why is half of the peroxisome population left in the mother cell while the remainder moves into the bud, what is the role of the dynamin Vps1 in peroxisome partitioning, can we design genetic screens to identify mutants with perturbed partitioning of peroxisomes and which proteins are deficient in these mutants?