Protean permeases: Diverse roles for membrane transport proteins in kinetoplastid protozoa

Abstract

Kinetoplastid parasites such as Trypanosoma brucei, Trypanosoma cruzi, and Leishmania species rely upon their insect and vertebrate hosts to provide a plethora of nutrients throughout their life cycles. Nutrients and ions critical for parasite survival are taken up across the parasite plasma membrane by transporters and channels, polytopic membrane proteins that provide substrate-specific pores across the hydrophobic barrier. However, transporters and channels serve a wide range of biological functions beyond uptake of nutrients. This article highlights the diversity of activities that these integral membrane proteins serve and underscores the emerging complexity of their functions.

Keywords: Channels; Drug sensitivity; Kinetoplastid parasites; Organelles; Sensing; Transporters.

Fig.

Diverse functions of membrane transport proteins in kinetoplastid parasites. A. Membrane transport proteins can serve different biological roles as importers of nutrients, exporters of metabolites, drugs, or xenobiotics, channels for ions or other solutes, drug transporters, or sensors of solutes. B. Transporters and channels can be located in various surface or internal membranes of distinct organelles. For illustration, the image displayed is that of a Leishmania promastigote, but the principle is the same regardless of the species or life cycle stage under consideration. Examples of specific transport proteins discussed in the text include the GT1 glucose transporter in the flagellum, nucleoside sugar transporters in the Golgi apparatus, the GT3 glucose transporter in the endoplasmic reticulum, amino acid transporters in the plasma membrane, the IP3 receptor in acidocalcisomes, the ADP/ATP exchanger in the inner mitochondrial membrane, and the TbHERG heme transporter in endosomes of T. brucei.