Fis1, DLP1, and Pex11p coordinately regulate peroxisome morphogenesis

Dynamin-like protein 1 (DLP1) and Pex11p beta function in morphogenesis of peroxisomes. In the present work, we investigated whether Fis1 is involved in fission of peroxisomes. Endogenous Fis1 was morphologically detected in peroxisomes as well as mitochondria in wild-type CHO-K1 and DLP1-defective ZP121 cells. Subcellular fractionation studies also revealed the presence of Fis1 in peroxisomes. Peroxisomal Fis1 showed the same topology, i.e., C-tail anchored membrane protein, as the mitochondrial one. Furthermore, ectopic expression of FIS1 induced peroxisome proliferation in CHO-K1 cells, while the interference of FIS1 RNA resulted in tubulation of peroxisomes, hence reducing the number of peroxisomes. Fis1 interacted with Pex11p beta, by direct binding apparently involving the C-terminal region of Pex11p beta in the interaction. Pex11p beta also interacted with each other, whereas the binding of Pex11p beta to DLP1 was not detectable. Moreover, ternary complexes comprising Fis1, Pex11p beta, and DLP1 were detected by chemical cross-linking. We also showed that the highly conserved N-terminal domain of Pex11p beta was required for the homo-oligomerization of Pex11p beta and indispensable for the peroxisome-proliferating activity. Taken together, these findings indicate that Fis1 plays important roles in peroxisome division and maintenance of peroxisome morphology in mammalian cells, possibly in a concerted manner with Pex11p beta and DLP1. (c) 2007 Elsevier Inc. All rights reserved.