Cell invasion by Trypanosoma cruzi amastigotes of distinct infectivities: studies on signaling pathways

Abstract

Trypanosoma cruzi metacyclic trypomastigotes of the major phylogenetic lineages use specific signaling pathways to invade host cells. Using a panel of drugs, we studied if the differences in the ability of extracellular amastigotes (EA) from G (T. cruzi I) and CL (T. cruzi II) strains to invade host cells could be associated to activation of specific signaling routes. Sonicated extracts from G or CL strain EA induced transient raises in HeLa cell intracellular Ca(2+) levels in a dose-dependent manner. Treatment of EA with drugs that affect Ca(2+) release from inositol-1,4,5-triphosphate-sensitive stores did not significantly affect the infectivity of either strain, whereas EA of both strains treated with ionomycin plus NH(4)Cl or nigericin that release Ca(2+) from acidocalcisomes had their infectivity reduced. Treatment of parasites with adenylate cyclase activator forskolin increased the infectivity of both strains towards HeLa cells. These data, taken together, suggest that, for host cell invasion, G and CL strain EA engage signaling pathways that lead to an increase of cyclic adenosine monophosphate and Ca(2+) mobilization from acidocalcisomes. Moreover, treatment of EA with genistein reduced by approximately 45% the invasion of HeLa cells by G but not by CL strain, implicating a protein tyrosine kinase in the process. In line with this, HeLa cell extracts contained a protein tyrosine kinase activity that mediated the phosphorylation of 87- and 175-kDa polypeptides of EA from G but not from CL strain. Regarding the target cell response, the activation of host PI3 kinase appears to be required for invasion by either strain as treatment of HeLa cells with wortmannin reduced EA infectivity. These data overall reinforce the concept that cell invasion by T. cruzi EA markedly differs from the process involving metacyclic trypomastigotes.

Trypanosoma cruzi uses macropinocytosis as an additional entry pathway into mammalian host cell

“…Although we observed a colocalization between amastigotes and Lucifer Yellow, this colocalization was more pronounced when we used trypomastigote. Many studies showed that, although capable of infecting a wide range of host cells, the mechanisms used by amastigotes may be different from those used by trypomastigotes, including molecules on the surface of host cell important for interaction, and protein kinase involved in the remodeling of the host cell cytoskeleton [38,39].…”

New Insights into Roles of Acidocalcisomes and Contractile Vacuole Complex in Osmoregulation in Protists

“…In this regard, it has been reported that acidocalcisome Ca 2+ has a role in host cell invasion. Depletion of acidocalcisome Ca 2+ by pretreatment of invasive stages of T. cruzi with ionomycin plus nigericin or ionomycin plus NH 4 Cl, inhibited invasion of host cells (Fernandes et al, 2006; Neira et al, 2002). In T gondii , knockout of TgA1, the enzyme necessary for pumping Ca 2+ into the organelle results in de-regulation of cytosolic calcium, altered microneme secretion, and decreased virulence (Luo et al, 2004).…”

Induction of phagocytic activity and nitric-oxide production in natural populations of Trypanosoma Cruzi I and II from the state of Paraná, Brazil

“…In other studies with T. cruzi I and II strains, metacyclic trypomastigotes from T. cruzi II were more infective than were those from T. cruzi I 33 . Conversely, FERNANDES et al 20 , using extracellular amastigotes of the same strains, demonstrated that T. cruzi I displayed much higher infectivity than T. cruzi II. Metacyclic trypomastigotes and amastigotes from these lineages depend on different signaling mechanisms to invade various types of host cells 19,20,33 .…”