Biology subjects

Malhotra, P.

Publications and source records attributed to Malhotra, P..

3 recordsLinked to original sources

bioRxiv2021

Involvement of translocon complex in hemoglobin import from infected erythrocyte cytoplasm into the Plasmodium parasite

Haemoglobin degradation is crucial for the growth and survival of Plasmodium falciparum in human erythrocytes. Although the process of Hb degradation has been studied in great detail, the mechanisms of Hb uptake remain ambiguous to date. Here, we characterized Heme Detoxification Protein (PfHDP), a protein localized in the parasitophorous vacuole, parasite food vacuole and infected erythrocyte cytosol for its role in Hb uptake. Immunoprecipitation of PfHDP-GFP fusion protein from a transgenic line using anti-GFP antibody and of Plasmodium parasite extract using anti-human Hb antibodies respectively, showed the association of PfHDP/Hb with each other as well as with the members of PTEX translocon complex. Some of these associations such as PfHDP/Hb and PfHDP/Pfexp-2 interactions were confirmed by in vitro protein-protein interaction tools. To know the roles of PfHDP and translocon complex in Hb import into the parasites, we next studied the Hb uptake by the parasite in PfHDP knock-down line using the GlmS ribozyme strategy. PfHDP knock-down significantly reduced the Hb uptake in these parasites in comparison to the wild type parasites. Further, the transient knock-down of one of the members of the translocon complex; PfHSP101 showed considerable reduction in Hb uptake. Morphological analysis of PfHDP-HA-GlmS transgenic parasites in the presence of GlcN showed food vacuole abnormalities and parasite stress, thereby causing a growth defect in the development of these parasites. Together, we implicate the translocon complex in the trafficking of PfHDP/Hb complex in the parasite and suggest a role for PfHDP in the uptake of Hb and parasite development. The study thus reveals new insights into the function of PfHDP, making it an extremely important target for developing new antimalarials.

molecular biology↗

bioRxiv2021

Artemisinin acts by inhibiting Plasmodium falciparum Ddi1, a retropepsin, resulting into the accumulation of ubiquitinated proteins

Reduced sensitivity of the human malaria parasite, Plasmodium falciparum, to Artemisinin and its derivatives (ARTs) threatens the global efforts towards eliminating malaria. ARTs have been shown to cause ubiquitous cellular and genetic insults, which results in the activation of the unfolded protein response (UPR) pathways. The UPR restores protein homeostasis, which otherwise would be toxic to cellular survival. Here, we interrogated the role of DNA-damage inducible protein 1 (PfDdi1), a unique proteasome-interacting retropepsin in mediating the actions of the ARTs. We demonstrate that PfDdi1 is an active A2 family protease that hydrolyzes ubiquitinated substrates. We further show that treatment with ARTs lead to the accumulation of ubiquitinated proteins in the parasites and blocks the destruction of the ubiquitinated substrates by PfDdi1. Besides, whereas the PfDdi1 is predominantly localised in the cytoplasm, exposure of the parasites to ARTs leads to DNA fragmentation and increased recruitment of the PfDdi1 into the nucleus. Furthermore, Ddi1 knock-out Saccharomyces cerevisiae cells are more suceptible to ARTs and the PfDdI1 protein robustly restores the corresponding functions in the knock-out cells. Together, these results show that ARTs act by inducing DNA and protein damage, and impairing the damage recovery by inhibiting the activity of PfDdi1, an essential ubiquitin-proteasome retropepsin.

cell biology↗

bioRxiv2020

Interaction of dengue NS3 with human RNA silencing machinery through HSPA1A

Viruses encode multiple proteins that interact with different host factors to aid in their establishment inside the host. Viral Suppressor of RNA silencing (VSR) are one such class of proteins that have been shown to interact with components of host machinery involved in post transcriptional gene silencing, a known antiviral defence mechanism. In the present study, we showed that dengue NS3, a known VSR not only interacts with HSPA1A, a cellular chaperone, but also modulates its expression levels. Further, we revealed HSPA1A associated with host RNA silencing machinery through its interaction with Argonaute proteins; Ago1, Ago2 and co-localizes with them in the cytoplasm of the cell. Together, these results provide evidence for involvement of other host partners in mediating VSR function of dengue NS3 and aid in deeper understanding of mechanisms underlying viral suppression of RNA silencing.

molecular biology↗