Pex14p is Not Required for Microautophagy and in Catalytic Amounts for Macropexophagy in Hansenula polymorpha

Abstract

We showed before that the two oppositely directed processes of peroxisome biogenesis and selective peroxisome degradation (macropexophagy) converge at the peroxisomal membrane protein Pex14p. Here we show that this protein is not required for peroxisomal degradation during nitrogen starvation-induced general autophagy, thereby limiting its function to the selective degradation process. Pex14p is present in two forms, namely an unmodified (Pex14p) and a phosphorylated form (Pex14pPi) that are differently induced during peroxisome proliferation. The data suggest that Pex14p is required for peroxisome biogenesis during organelle proliferation and Pex14pPi in macropexophagy. Finally, we show that macropexophagy is not coupled to normal peroxisome assembly and is required in only catalytic amounts to allow initiation of the selective peroxisome degradation process.