TcAMPK: A cellular energy homeostasis hub regulator with unique characteristics in Trypanosoma cruzi

Abstract

The AMP-activated protein kinase (AMPK) is a heterotrimeric enzyme involved in maintaining energy homeostasis in response to different stresses in many organisms. During the transition between the mammalian host and the insect vector, Trypanosoma cruzi, the causative agent of Chagas disease, faces different types of environmental fluctuations, all of which prompt the parasite to remodel its metabolism to adapt, survive and differentiate into the next stages of its life cycle. Recently, it was shown that Trypanosoma brucei AMPK is involved in the differentiation from the bloodstream slender to stumpy stage and in surface protein expression changes in response to nutritional stress. This underscores the relevance of AMPK for parasite life cycle progression. We identified four genes for the AMPK subunits of T. cruzi (α1 and α2 catalytic subunits, β and γ regulatory subunits). The β and γ subunits are largely conserved in their domain structure relative to the mammalian orthologs. However, the alpha subunits show significant sequence, structure and evolutionary differences from the human counterparts. The presence of these subunits in epimastigotes was confirmed by several techniques. TcAMPKα1 over-expressing epimastigotes showed a lower growth rate in basal culture conditions compared to the control, while α2 over-expression had the opposite effect. We found there is upregulation of AMPK activity under starvation, which is prevented if glucose is present in the culture medium. Each of these subunits could complement the ?glucose dependent? phenotype of S. cerevisiae conditional mutants lacking the respective subunit of the AMPK ortholog SNF1. Starvation and Monodansylcadaverine incorporation assays with AMPKα over-expressing parasites also showed a possible role of AMPK in autophagy. Finally, we explore the pathways in which TcAMPK may be involved using in silico analysis of putative substrates. Our results open the door to the study of the AMPK signaling pathway in Trypanosoma cruzi.