σ1- and μ1-adaptin homologues of Leishmania mexicana are required for parasite survival in the infected host

Abstract

The sorting of membrane-bound proteins from the trans-Golgi network to lysosomal/endosomal compart. ments is achieved by preferential inclusion into clathrin-coated vesicles. Contained within the cytoplasmic domains of such proteins, specific sequence motifs have been identified (tyrosine-based and/or di-leucine-based) that are essential for targeting and are recognized by a family of heterotetrameric adaptor complexes, which then recruit clathrin. These cytosolic protein complexes, which have been found in a wide variety of higher eukaryotic organisms, are essential for the development of multicellular organisms. In trypanosomatids, the adaptin-mediated sorting of proteins is largely uncharacterized. In order to identify components of the adaptor-complex machinery, this study reports the cloning and characterization of σ1- and μ1-adaptin gene homologues from the eukaryotic protozoan parasite, Leishmania mexicana. Generation of σ1- and μ1-adaptin gene deletion mutants shows that these promastigote parasites are viable in culture, but are unable to establish infection of macrophages or mice, indicating that adaptin function is crucial for pathogenesis in these unicellular organisms.