The same protein that directs the biogenesis of peroxisomes, essential detoxifiers of the cell, also hitches the organelle to its myosin motor for transport into daughter cells, show Chang et al.
The beloved model Saccharomyces cerevisiae does have limitations—one being that its peroxisome receptor for the myosin V motor has no known homologues outside of this fungus family. To figure out how other eukaryotes accomplish peroxisome inheritance, Chang et al. turned to the yeast Yarrowia lipolytica and a new player, Pex3B.
Pex3B was recently identified as a paralogue of Pex3, the highly conserved protein responsible for the earliest stages of peroxisome genesis—forming new membrane at the ER. Chang et al. found that, like Pex3, Pex3B is a peroxisomal integral membrane protein. Deleting Pex3B resulted in long, tubular peroxisomes, which were conspicuously absent from the bud tips of dividing cells. Closer inspection of inheritance in pex3BΔ cells revealed that the organelles had trouble entering the bud and, once there, ceased moving altogether, with the stretched peroxisomes often straddling the mother-bud neck.
These movement troubles hinted at a role for Pex3B as the organelle's myosin V receptor. Not only did Pex3B bind to the motor, but the team showed that Pex3 did as well. In fact, when overexpressed, Pex3 compensated for the inheritance defect of the pex3BΔ cells. Pex3's paralogue allowed Chang et al. to uncover its hidden talent as a myosin receptor, which establishes a direct temporal link between biogenesis and transfer. The authors propose Pex3's dual activities ensure that new, fresh peroxisomes move into new cells, while old, oxidatively damaged organelles remain behind.
