Real time imaging reveals a peroxisomal reticulum in living cells

We have directly imaged the dynamic behavior of a variety of morphologicall y different peroxisomal structures in HepG2 and COS-7 cells transfected wit h a construct encoding GFP bearing the C-terminal peroxisomal targeting sig nal 1. Real time imaging revealed that moving peroxisomes interacted with e ach other and were engaged in transient contacts, and at higher magnificati on, tubular peroxisomes appeared to form a peroxisomal reticulum, Local rem odeling of these structures could be observed involving the formation and d etachment of tubular processes that interconnected adjacent organelles. Inh ibition of cytoplasmic dynein based motility by overexpression of the dynac tin subunit, dynamitin (p50), inhibited the movement of peroxisomes in vivo and interfered with the reestablishment of a uniform distribution of perox isomes after recovery from nocodazole treatment. Isolated peroxisomes moved in vitro along microtubules in the presence of a microtubule motor fractio n. Our data reveal that peroxisomal behavior in vivo is significantly more dynamic and interactive than previously thought and suggest a role for the dynein/dynactin motor in peroxisome motility.