https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/69 Mon, 27 Apr 2026 15:57:58 GMT 2026-04-27T15:57:58Z https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1562 Title: Protein kinase PfPK2 mediated signalling is critical for host erythrocyte invasion by malaria parasite Authors: Sharma, Pushkar; Rawat, Rahul Singh; Gupta, Ankit; Antil, Neelam; Bhatnagar, Sonika; Singh, Monika; Rawat, Akanksha; Prasad, T S Keshava Abstract: Signalling pathways in malaria parasite remain poorly defined and major reason for this is the lack of understanding of the function of majority of parasite protein kinases and phosphatases in parasite signalling and its biology. In the present study, we have elucidated the function of Protein Kinase 2 (PfPK2), which is known to be indispensable for the survival of human malaria parasite Plasmodium falciparum. We demonstrate that it is involved in the invasion of host erythrocytes, which is critical for establishing infection. In addition, PfPK2 may also be involved in the maturation of the parasite post-invasion. PfPK2 regulates the release of microneme proteins like Apical Membrane Antigen 1 (AMA1), which facilitates the formation of Tight Junction between the merozoite and host erythrocyte- a key step in the process of invasion. Comparative phosphoproteomics studies revealed that PfPK2 may be involved in regulation of several key proteins involved in invasion and signalling. Furthermore, PfPK2 regulates the generation of cGMP and the release of calcium in the parasite, which are key second messengers for the process of invasion. These and other studies have shed light on a novel signalling pathway in which PfPK2 acts as an upstream regulator of important cGMP-calcium signalling, which plays an important role in parasite invasion. Sun, 01 Jan 2023 00:00:00 GMT https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1562 2023-01-01T00:00:00Z https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1258 Title: Phosphorylation of Rhoptry Protein RhopH3 Is Critical for Host Cell Invasion by the Malaria Parasite Authors: Sharma, Pushkar; Ekka, Roseleen; Gupta, Ankit; Bhatnagar, Sonika; Malhotra, Pawan Abstract: Merozoites formed after asexual division of the malaria parasite invade the host red blood cells (RBCs), which is critical for initiating malaria infection. The process of invasion involves specialized organelles like micronemes and rhoptries that discharge key proteins involved in interaction with host RBC receptors. RhopH complex comprises at least three proteins, which include RhopH3. RhopH3 is critical for the process of red blood cell (RBC) invasion as well as intraerythrocytic development of human malaria parasite Plasmodium falciparum It is phosphorylated at serine 804 (S804) in the parasite; however, it is unclear if phosphorylation regulates its function. To address this, a CRISPR-CAS9-based approach was used to mutate S804 to alanine (A) in P. falciparum Using this phosphomutant (R3_S804A) of RhopH3, we demonstrate that the phosphorylation of S804 is critical for host RBC invasion by the parasite but not for its intraerythrocytic development. Importantly, the phosphorylation of RhopH3 regulates its localization to the rhoptries and discharge from the parasite, which is critical for RBC invasion. We also identified P. falciparum CDPK1 (PfCDPK1) as a possible candidate kinase for RhopH3-S804 phosphorylation and found that it regulates RhopH3 secretion from the parasite. These findings provide novel insights into the role of phosphorylation in rhoptry release and invasion, which is poorly understood.IMPORTANCE Host cell invasion by the malaria parasite is critical for establishing infection in human host and is dependent on discharge of key ligands from organelles like rhoptry and microneme, and these ligands interact with host RBC receptors. In the present study, we demonstrate that phosphorylation of a key rhoptry protein, RhopH3, is critical for host invasion. Phosphorylation regulates its localization to rhoptries and discharge from the parasite. Wed, 01 Jan 2020 00:00:00 GMT https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1258 2020-01-01T00:00:00Z https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1257 Title: Protein kinase TgCDPK7 regulates vesicular trafficking and phospholipid synthesis in Toxoplasma gondii Authors: Sharma, Pushkar; Bansal, Priyanka; Antil, Neelam; Kumar, Manish; Yamaryo-Botté, Yoshiki; Rawat, Rahul Singh; Pinto, Sneha; Datta, Keshava K; Katris, Nicholas J; Botté, Cyrille Y; Prasad, T S Keshava Abstract: Apicomplexan parasites are causative agents of major human diseases. Calcium Dependent Protein Kinases (CDPKs) are crucial components for the intracellular development of apicomplexan parasites and are thus considered attractive drug targets. CDPK7 is an atypical member of this family, which initial characterization suggested to be critical for intracellular development of both Apicomplexa Plasmodium falciparum and Toxoplasma gondii. However, the mechanisms via which it regulates parasite replication have remained unknown. We performed quantitative phosphoproteomics of T. gondii lacking TgCDPK7 to identify its parasitic targets. Our analysis lead to the identification of several putative TgCDPK7 substrates implicated in critical processes like phospholipid (PL) synthesis and vesicular trafficking. Strikingly, phosphorylation of TgRab11a via TgCDPK7 was critical for parasite intracellular development and protein trafficking. Lipidomic analysis combined with biochemical and cellular studies confirmed that TgCDPK7 regulates phosphatidylethanolamine (PE) levels in T. gondii. These studies provide novel insights into the regulation of these processes that are critical for parasite development by TgCDPK7. Fri, 01 Jan 2021 00:00:00 GMT https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1257 2021-01-01T00:00:00Z https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1012 Title: PfCDPK1 mediated signaling in erythrocytic stages of Plasmodium falciparum Authors: Sharma, Pushkar; Kumar, Sudhir; Kumar, Manish; Ekka, Roseleen; Dvorin, Jeffrey D.; Paul, Aditya S.; Madugundu, Anil K.; Gilberger, Tim; Gowda, Harsha; Duraisingh, Manoj T.; Prasad, T.S. Keshava Abstract: Calcium Dependent Protein Kinases are key effectors of calcium signaling in malaria parasite. PfCDPK1 is critical for asexual development of Plasmodium falciparum, but its precise function and substrates remain largely unknown. Using a conditional knockdown strategy, we here establish that this kinase is critical for the invasion of host erythrocytes. Furthermore, using a multidisciplinary approach involving comparative phosphoproteomics we gain insights into the underlying molecular mechanisms. We identify substrates of PfCDPK1, which includes proteins of Inner Membrane Complex and glideosome-actomyosin motor assembly. Interestingly, PfCDPK1 phosphorylates PfPKA regulatory subunit (PfPKA-R) and regulates PfPKA activity in the parasite, which may be relevant for the process of invasion. This study delineates the signaling network of PfCDPK1 and sheds light on mechanisms via which it regulates invasion.Calcium dependent protein kinase 1 (CDPK1) plays an important role in asexual development of Plasmodium falciparum. Using phosphoproteomics and conditional knockdown of CDPK1, the authors here identify CDPK1 substrates and a cross-talk between CDPK1 and PKA, and show the role of CDPK1 in parasite invasion. Sun, 01 Jan 2017 00:00:00 GMT https://dspace.nii.res.in//https://dspace.nii.res.in/handle/123456789/1012 2017-01-01T00:00:00Z