Characterization of unusual families of ATG8-like proteins and ATG12 in the protozoan parasite Leishmania major

• Autor(a) principal: Williams, Roderick A. M.
• Data de Publicação: 2009
• Outros Autores: Woods, Kerry L., Juliano, Luiz [UNIFESP], Mottram, Jeremy C., Coombs, Graham H.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UNIFESP
• dARK ID: ark:/48912/001300000g9sq
• Texto Completo: http://dx.doi.org/10.4161/auto.5.2.7328; http://repositorio.unifesp.br/handle/11600/42774
• topic: autophagy; leishmania; protozoan parasite; ATG4; ATG8; ATG12

Leishmania major possesses, apparently uniquely, four families of ATG8-like genes, designated ATG8, ATG8A, ATG8B and ATG8C, and 25 genes in total. L. major ATG8 and examples from the ATG8A, ATG8B and ATG8C families are able to complement a Saccharomyces cerevisiae ATG8-deficient strain, indicating functional conservation. Whereas ATG8 has been shown to form putative autophagosomes during differentiation and starvation of L. major, ATG8A primarily form puncta in response to starvation-suggesting a role for ATG8A in starvation-induced autophagy. Recombinant ATG8A was processed at the scissile glycine by recombinant ATG4.2 but not ATG4.1 cysteine peptidases of L. major and, consistent with this, ATG4.2-deficient L. major mutants were unable to process ATG8A and were less able to withstand starvation than wad-type cells. GFP-ATG8-containing puncta were less abundant in ATG4.2 overexpression lines, in which unlipidated ATG8 predominated, which is consistent with ATG4.2 being an ATG8-deconjugating enzyme as well as an ATG8A-processing enzyme. In contrast, recombinant ATG8, ATG8B and ATG8C were all processed by ATG4.1, but not by ATG4.2. ATG8B and ATG8C both have a distinct subcellular location close to the flagellar pocket, but the occurrence of the GFP-labeled puncta suggest that they do not have a role in autophagy. L. major genes encoding possible ATG5, ATG10 and ATG12 homologues were found to complement their respective S. cerevisiae mutants, and ATG12 localized in part to ATG8-containing puncta, suggestive of a functional ATG5-ATG12 conjugation pathway in the parasite. L. major ATG12 is unusual as it requires C-terminal processing by an as yet unidentified peptidase.