Characterization of Trypanosoma brucei PEX14 and its role in the import of glycosomal matrix proteins.

It has been shown previously in various organisms that the peroxin PEX14 is a component of a docking complex at the peroxisomal membrane, where it is involved in the import of matrix proteins into the organelle after their synthesis in the cytosol and recognition by a receptor. Here we present a characterization of the Trypanosoma brucei homologue of PEX14. It is shown that the protein is associated with glycosomes, the peroxisome-like organelles of trypanosomatids in which most glycolytic enzymes are compartmentalized. The N-terminal part of the protein binds specifically to TbPEX5, the cytosolic receptor for glycosomal matrix proteins with a peroxisome-targeting signal type 1 (PTS-1). TbPEX14 mRNA depletion by RNA interference results, in both bloodstream-form and procyclic, insect-stage T. brucei, in mislocalization of glycosomal proteins to the cytosol. The mislocalization was observed for different classes of matrix proteins: proteins with a C-terminal PTS-1, a N-terminal PTS-2 and a polypeptide internal I-PTS. The RNA interference experiments also showed that TbPEX14 is essential for the survival of bloodstream-form and procyclic trypanosomes. These data indicate the protein's great potential as a target for selective trypanocidal drugs.