Activation of Host Cell Phosphatidylinositol 3-Kinases byTrypanosoma cruzi Infection

Abstract

Trypanosoma cruzi, the causative agent of Chagas' disease in humans, is an intracellular protozoan parasite with the ability to invade a wide variety of mammalian cells by a unique and remarkable process in cell biology that is poorly understood. Here we present evidence suggesting a role for the host phosphatidylinositol (PI) 3-kinases during T. cruzi invasion. The PI 3-kinase inhibitor wortmannin marked inhibited T. cruzi infection when macrophages were pretreated for 20 min at 37°C before inoculation. Infection of macrophages with T. cruzi markedly stimulated the formation of the lipid products of the phosphatidylinositol (PI) 3-kinases, PI 3-phospate , PI 3,4-biphosphate, and PI 3,4,5-triphosphate, but not PI 4-phosphate or PI 4,5-biphosphate. This activation was inhibited by wortmannin. Infection with T. cruzi also stimulated a marked increase in the in vitro lipid kinase activities that are present in the immunoprecipitates of anti-p85 subunit of class I PI 3-kinase and anti-phosphotyrosine. In addition, T. cruzi invasion also activated lipid kinase activity found in immunoprecipitates of class II and class III PI 3-kinases. These data demonstrate that T. cruzi invasion into macrophages strongly activates separated PI 3-kinase isoforms. Furthermore, the inhibition of the class I and class III PI 3-kinase activities abolishes the parasite entry into macrophages. These findings suggest a prominent role for the host PI 3-kinase activities during the T. cruzi infection process.Trypanosoma cruzi, an intracellular protozoan parasite that infects humans and other mammalian hosts, is the etiologic agent of Chagas' disease that is a major public health problem in Latin America (1). This parasite is now viewed as an emerging human pathogen of HIV-1-infected individuals as it can be transmitted through blood transfusions (2). This unicellular parasite presents three developmental stages; epimastigote and amastigote forms correspond to proliferative stages found in the invertebrate and vertebrate hosts, respectively. The trypomastigote forms are infective and invade different host cell types, first macrophages, in order to replicate (3).How T. cruzi trypomastigotes signal to gain entry and survive in their host is not completely understood. However, some evidence suggests that T. cruzi interacts with different signaling systems of the host. It has been shown that the transforming growth factor ␤-receptor signaling pathway is essential for T. cruzi invasion (4). Activation of a calcium-dependent host cell pathway by T. cruzi has also been reported (3, 5). In addition, T. cruzi invasion has been shown to induce tyrosine phosphorylation of macrophage proteins (6), as well as activation of the mitogen-activated protein kinase pathway (7). Thus, the blockade of tyrosine kinase and mitogen-activated protein kinase activities in the host macrophage by inhibitors (7,8) ablate the infection of these cells by T. cruzi, suggesting that activation of kinase pathways is an important event in this process. Invasion of T. cruzi into...

Trypanosoma cruzitrans-sialidase: A potent and specific survival factor for human Schwann cells by means of phosphatidylinositol 3-kinase/Akt signaling

“…Thus, TS promotes Schwann-cell survival by activating a signal-transduction cascade used by authentic cell survival-promoting mammalian neurotrophic growth factors (31). Although T. cruzi infection of macrophages triggers PI3K activation (32), it remains to be determined whether TS is the active T. cruzi-activating factor in those cell types. (A) GFP-and GFP͞AktKI-transfected Schwann cells were maintained in 0.1% FCS for 48 hr without tetracycline (to induce GFP and AktKI expression) in the absence (GFP and AktKI, respectively) or presence (GFP͞cTS and AktKI͞cTS) of 500 ng͞ml of cTS for 2 min.…”

A century of research: what have we learned about the interaction of Trypanosoma cruzi with host cells?

“…It is worth mentioning in this context that the invasion of host cells by MTs of the CL strain depends on tyrosine phosphorylation and the IP � -dependent (1,4,5-inositol-triphosphate) release of calcium from endoplasmic reticulum (ER) stores, whereas MTs of the G strain engage adenylate cyclase and cause calcium to be mobilised from acidocalcisomes (Neira et al 2002). No comparative data between both strains is evaluable for TCTs, but inhibitors of class I and class III PI�-K activities block the entry of the parasite into macrophages, suggesting the involvement of different isoforms of this kinase (Todorov et al 2000). On the other hand, it seems that calcium mobilisation from acidocalcisomes, but not from the ER, is important for cellular invasion by extracellular amastigotes of either the G or CL strains (Mor-Mortara et al 2005, Fernandes et al 200�, Scharfstein et al 200�, 2008, Scharfstein & Lima 2008.…”

“…�dditional evidence suggests the participation of components of the early endocytic trafficking pathway, such as dynamin and Rab5, and indicates that the lysosomal process might be both more elaborate and downstream of earlier events (Wilkowsky et al 2002). Previous studies (Todorov et al 2000, Wilkowsky et al 2001) have used a quantitative approach to iden-2001) have used a quantitative approach to idenhave used a quantitative approach to identify the role of phosphatidyl-inositol �-kinase (PI�-K) (Woolsey et al 200�) in the lysosomal pathway and ob- Woolsey et al 200�) in the lysosomal pathway and obin the lysosomal pathway and observed that this key cellular component is involved in a lysosome-independent T. cruzi internalisation pathway utilised by TCTs. Trypomastigotes that use this route mobilise phosphorylated inositides during the formation of the PV.…”

Infection and invasion mechanisms of Trypanosoma cruzi in the congenital transmission of Chagas' disease: A proposal

“…During cell invasion, phosphoinositol 3-kinases (PI 3Ks) are also activated; inhibition of these kinases blocks the parasite's internalization (Todorov, et al 2000;Yoshida, 2006). The regulatory sub-unit of PI-3K, p85, co-localizes with actin filaments at the sites of parasite entry into macrophages (Vieira, et al 2002).…”