Tubulo-reticular clusters of peroxisomes in living COS-7 cells: Dynamic behavior and association with lipid droplets

We characterized more complex peroxisomal structures, i.e., tubulo-reticula r peroxisomal clusters, in greater detail under in vivo conditions in COS-7 cells that were transfected with a GFP-PTS1 fusion protein. Live cell imag ing revealed the dynamic nature of peroxisomal clusters and allowed a detai led analysis of the motile properties of a heterogeneous peroxisome populat ion. Furthermore, peroxisomal clusters were found to be associated with lip id droplets. The frequency of peroxisomal clusters correlated with an incre ase in cell density and in the size of lipid droplets. These data provide f urther evidence for the dynamic nature of the peroxisomal compartment and i ndicate that peroxisomal clusters have a function in lipid metabolism.