Toxoplasma gondiiinduces prolonged host epidermal growth factor receptor signalling to prevent parasite elimination by autophagy: Perspectives for in vivo control of the parasite

Abstract

Toxoplasma gondii causes retinitis and encephalitis. Avoiding targeting by autophagosomes is key for its survival because T. gondii cannot withstand lysosomal degradation. During invasion of host cells, T. gondii triggers epidermal growth factor receptor (EGFR) signalling enabling the parasite to avoid initial autophagic targeting. However, autophagy is a constitutive process indicating that the parasite may also use a strategy operative beyond invasion to maintain blockade of autophagic targeting. Finding that such a strategy exists would be important because it could lead to inhibition of host cell signalling as a novel approach to kill the parasite in previously infected cells and treat toxoplasmosis. We report that T. gondii induced prolonged EGFR autophosphorylation. This effect was mediated by PKCα/PKCβ ➔ Src because T. gondii caused prolonged activation of these molecules and their knockdown or incubation with inhibitors of PKCα/PKCβ or Src after host cell invasion impaired sustained EGFR autophosphorylation. Addition of EGFR tyrosine kinase inhibitor (TKI) to previously infected cells led to parasite entrapment by LC3 and LAMP‐1 and pathogen killing dependent on the autophagy proteins ULK1 and Beclin 1 as well as lysosomal enzymes. Administration of gefitinib (EGFR TKI) to mice with ocular and cerebral toxoplasmosis resulted in disease control that was dependent on Beclin 1. Thus, T. gondii promotes its survival through sustained EGFR signalling driven by PKCα/β ➔ Src, and inhibition of EGFR controls pre‐established toxoplasmosis.

Recent Advances in the Roles of Autophagy and Autophagy Proteins in Host Cells During Toxoplasma gondii Infection and Potential Therapeutic Implications

“…However, autophagy is a constitutive process, indicating that the parasite likely uses additional mechanisms to maintain a blockade of autophagic targeting. Indeed, T. gondii causes prolonged EGFR autophosphorylation in mammalian cells that is functionally relevant, as the addition of EGFR tyrosine kinase inhibitors (TKIs) 6 h after challenge with T. gondii resulted in the killing of the parasite ( Lopez Corcino et al, 2019a ). This process involved entrapment of the PV by a double-membrane structure compatible with an autophagosome, accumulation of LC3 and LAMP-1 around the PV, and pathogen killing dependent on ULK1, Beclin 1, and lysosomal enzymes ( Lopez Corcino et al, 2019a ).…”

The Host Autophagy During Toxoplasma Infection

“…Parasites can induce the phosphorylation of EGFR in host cells by secreting several proteins containing multiple domains homologous to EGFR, such as MIC3 and MIC6. PI3K-mediated Akt phosphorylation can activate the autophagosome negative regulator mTORC1, which leads to reverse regulation of autophagy (Muniz-Feliciano et al, 2013;Coppens, 2017;Lopez Corcino et al, 2019). Thus, the Akt signaling pathway is critical for escaping host autophagy to promote parasite survival (Figure 5 I).…”

“…They prevent T. gondii from becoming a target (Portillo et al, 2017). At the later stage of the intracellular phase of T. gondii, EGFR autophosphorylation is maintained through prolonged PKCα/ PKCβ-Src signaling, which in turn promote the survival of Toxoplasma through Akt (Lopez Corcino et al, 2019;Figure 5 II).…”

Toxoplasma Gondii ROP17 Promotes Autophagy via the Bcl-2–Beclin 1 Pathway

“…To determine whether autophagy occurs in tachyzoite-infected murine cell models, para n-embedded sections of the small intestine were prepared for the immunohistochemical detection of autophagy markers. Beclin 1 and LC3B are markers of autophagy since beclin1 is involved in the initial step of autophagosome formation and LC3 forms puncta on the autophagosome membrane [17]. In addition, the ubiquitin-binding protein p62, which functions as a molecular adaptor for autophagic machinery and its substrates, has been widely used as a biochemical marker for general autophagy detection [18].…”