Thrombospondin‐1 Plays an Essential Role in Hippo Signaling During the Early Phase of Trypanosoma cruzi Infection in Heart Endothelial Cells

Abstract

Trypanosoma cruzi is an obligate intracellular hemoflagellate parasite which cause Chagas disease. This neglected tropical disease causes severe morbidity and mortality in endemic regions. 30% of chronically infected people suffer from cardiac disorder. Chagas heart diseasecan lead to sudden death due to cardiac arrhythmias or progressive heart failure. Invasive trypomastigotes released from infected cells can be carried in vascular endothelial system to infect neighboring and distant cells. During the process of cellular infection, the parasite induces host cells to increase the levels of host thrombospondin‐1 (TSP‐1) to enable the process of infection. TSP‐1 plays important roles in the functioning of vascular cells including vascular endothelial cells with important implications in cardiovascular health. Hippo signaling components, including yes‐associated protein 1 (YAP)/transcriptional coactivator with PDZ‐binding motif (TAZ), which are upstream of TSP‐1 have been linked to the pathophysiology of heart disease. The molecular mechanisms by which T. cruzi signals and eventually infect heart endothelial cells remain unknown. To evaluate the importance of TSP‐1 expression in heart endothelial cells during the process of T. cruzi infection, we challenge heart endothelial cells prepared from Wild Type and TSP‐1 Knockout mouse (MHEC) to invasive T. cruzi trypomastigotes at different time points and evaluated changes in the Hippo signaling cascade using immunoblotting and immunofluorescence assays. We found that the parasite turned off the hippo signaling pathway in TSP‐1KO heart endothelial cells. The levels of SAV1 and MOB1A increased to a maximum of 2.70±0.23 and 5.74±1.45 fold at 3 and 6 h, respectively, in TSP‐1KO MHEC compared to WT MHEC following parasite challenge. This was accompanied by a significant continuous increase in the nuclear translocation of downstream effector molecule YAP to a maximum mean nuclear fluorescence intensity of 10.14±0.40 at 6 h compared to wild type cells. Besides this, we found that increased nuclear translocated YAP significantly colocalized with the transcription co‐activator molecule pan‐TEAD with a maximum Pearson's correlation coefficient of 0.51±0.06 at 6 h compared to YAP‐Pan‐TEAD colocalization in the WT MHEC, which decreased significantly with to a minimum Pearson's correlation coefficient of 0.30±0.01 at 6 h. Our finding suggests that upregulated TSP‐1 is essential for the regulation of the hippo signaling pathway during the early phase of infection. These studies advance our understanding of the Host‐Parasite molecular interactions occurring between heart endothelial cells and T. cruzi in the presence and absence of TSP‐1. Taken together, this further supports our concept that an increase in the level of TSP‐1 induced by the parasite is essential for T. cruzi infection and pathogenesis.

EhrlichiaWnt short linear motif ligand mimetic deactivates the Hippo pathway to engage the anti-apoptotic Yap-GLUT1-BCL-xL axis

“…The Hippo pathway is well known for its role in cancer, but has recently been implicated in viral infections, including Hepatitis B virus (HBV), Hepatitis C virus (HCV), Human papillomavirus (HPV), Epstein-Barr virus (EBV), and Kaposi Sarcomaassociated herpesvirus (KSHV) (37). However, there are only a few reports of Hippo exploitation by parasites, fungi and bacteria (38)(39)(40). Yap activation by viruses has been reported, but the precise mechanism whereby deactivation of Hippo signaling occurs to activate Yap remains unclear (37).…”