Biology subjects

Behl, A.

Publications and source records attributed to Behl, A..

8 recordsLinked to original sources

bioRxiv2025

Plasmodium Repetome: A mysterious space with a wealth of information

Eukaryotic proteomes harbour repetitive stretches of amino acids that may play critical roles in the biology of that organism. While several tandem repeats (TR) are known to contribute to protein structure and function, information about the vast majority of repeat regions remains obscure. In this article, we have analysed the repeat content of different Plasmodium species and found the leading human malaria-causing P. falciparum (Pf) and P. vivax to be exceptionally rich in TR regions (>40% TR containing proteins). Detailed analysis of Pf repetome showed this intracellular parasite to carry longer TRs, several of which were present in exported proteins important for parasite survival and immune evasion. The repeat regions of Pf were enriched in acidic amino acids and asparagine (Asn), where Asn was more abundant in short and intermediate TRs, suggesting an evolutionary bias influenced by replication slippage and positive selection. Gene ontology analysis of TR containing Pf proteins helped us to understand their cellular localization along with the molecular and biological processes they are involved in. The Pf variable surface antigen families with roles in important pathogenic processes like cytoadherence, immune evasion etc. had low repeat content present within seroreactive peptides. Three-dimensional structure predictions of TR regions revealed several repeats to adopt ordered super-secondary conformations that are known to facilitate intermolecular interactions. Overall, this is a comprehensive study attempting to gain insights on the importance of TRs in malaria parasite biology and suggests a novel route to understanding protein function through the characterization of repeat content.

bioinformatics↗

bioRxiv2024

A first-in-Plasmodium study on tRNA intron splicing endonuclease PfTSEN1 and its substrate expression in clinical stage malaria

Mature tRNAs play critical role in several cellular processes including protein translation, post-translational-modifications and programmed-cell-death. Maturation of pre-tRNAs require removal of 5-leaders, 3-trailers, splicing of introns and addition of conserved 3-terminal CCA sequence. The tRNA splicing mechanism, an essential step in tRNA maturation govern by a tRNA splicing endonuclease. While the existence of functional tRNA splicing endonuclease(s) in Plasmodium falciparum has not been identified, its significance in other eukaryotes suggests a potential role in tRNA splicing event. Our study identified total tRNAs in Plasmodium and characterize a PftRNA splicing endonuclease (annotated as PfTSEN1) recognised recently as a component of ribonucleoprotein (RNP) complex, and synthesized a naphthoquinone derivative as a novel anti-malarial compound ( TSENi) targeting the functional activity of this protein. Enzyme activity assays elucidated that PfTSEN1 catalyses splicing of in vitro transcribed pre-tRNAleu, the expression of which was confirmed during the clinical stages of malaria parasite by RT-PCR. Interestingly, TSENi binds to and inhibits enzymatic activity of PfTSEN1, and showed potent anti-malarial activity against chloroquine-sensitive 3D7 and resistant strains Dd2 of P. falciparum. Overall, our study deliver key knowledge towards the functional role of PftRNA splicing endonuclease, and its inhibitor TSENi as potent anti-malarial.

molecular biology↗

bioRxiv2023

Host inducible-HSP70A1A is an irresistible drug target to combat SARS-CoV-2 infection and pathogenesis

One of the fundamental mechanisms developed by the host to contain the highly infectious and rapidly proliferating SARS coronavirus is elevation of body temperature, a natural fallout of which is Heat Shock Protein (HSP) over-expression. Here, for the first time, we demonstrate that the SARS-CoV-2 virus exploits the host Hsp70 chaperone for its entry and propagation and blocking it can combat the infection. SARS-CoV-2 infection as well as febrile temperature enhanced Hsp70 overexpression in host Vero E6 cells. In turn, Hsp70 overexpression elevated the host cell autophagic response that is a prerequisite for viral propagation. Suppressive and prophylactic treatment of Vero E6 cells with HSP70 inhibitor PES-Cl, a small molecule derivative of Pifithrin , abrogated viral infection more potently than the currently used drug Remdesivir by suppressing host HSP70 and autophagic response. In conclusion, our study not only provides a fundamental insight into the role of host Hsp70 in SARS-CoV-2 pathogenesis, it paves the way for the development of potent and irresistible anti-viral therapeutics.

microbiology↗

bioRxiv2022

Chaperonin activity of Plasmodium prefoldin complex is essential to guard proteotoxic stress response and presents a new target for drug discovery

The intraerythrocytic growth of malaria parasite is challenged by the presence of proteotoxic stress and intrinsically unstructured proteins in the cytoplasm due to formation of toxic heme during haemoglobin digestion. To overcome the unavoidable stress and maintain the cellular protein homeostasis, parasite encodes for a number of chaperones and co-chaperones. Here, we functionally characterize the Plasmodium falciparum prefoldins (PfPFD1-6), a hexameric co-chaperone complex, for their role in protein homeostasis. We demonstrate that PfPFD1-6 localise to cytosol of the parasite and the subunits perform an orchestrated interaction (-PFD3-PFD2-PFD1-PFD5-PFD6-PFD4-) to form an active jelly-fish like complex. Biperiden, an N-propylpiperidine analogue identified by chemotype search from FDA, strongly binds and restricts the formation of prefoldin complex and inhibited its interaction with the substrates, PfMSP-1 and -tubulin-I. Biperiden treatment potently inhibited the in vitro (IC50: 1M) and in vivo growth of malaria parasite. Thus, this study provides novel virtues towards understanding the role of PfPFDs in regulating protein homeostasis and opens new avenues for drug discovery against malaria.

molecular biology↗

bioRxiv2022

Human malaria parasite cold shock protein plays an essential role in asexual and sexual stage development and presents an excellent druggable target

Cold shock proteins are well characterized in bacteria, plants and humans, however there is no information on their existence and role in malaria parasite. Here, we have delineated the function of a novel cold shock protein of Plasmodium falciparum (Pf) which we have annotated PfCoSP. Our results show that recombinant PfCoSP has both DNA and RNA binding activity, and also interacts with alpha and beta tubulin of Pf. PfCoSP binds with RNA and alpha tubulin simultaneously to form a complex. Expression of PfCoSP was found during asexual blood stages and gametocyte stages of malaria parasite. PfCoSP expression up-regulates many folds upon cold treatment, suggesting its role during hypothermic cold shock. Interestingly, PfCoSP showed binding with human cold shock protein LIN28A inhibitor LI71 that also inhibits PfCSP -alpha/beta tubulin interactions. LI71 showed antimalarial activity against asexual blood stage and gametocyte stage suggesting its multi-stage, transmission-blocking potential. We propose that PfCoSP may form a workbench for translation during cold stress via its interactions with target mRNAs and the cytoskeleton protein tubulin.

molecular biology↗

bioRxiv2022

'Erythritol, a safe natural sweetener exhibits multi-stage anti-malarial activity by blocking Plasmodium falciparum membrane transporter 'aquaporin

The increased resistance of human malaria parasite Plasmodium falciparum to currently used drugs necessities the development of novel anti-malarials. In the present study, we examine the potential of erythritol, a sugar substitute, for therapeutic intervention that target a multifunctional transporter protein Plasmodium aquaglyceroporin (PfAQP) responsible for maintaining hydro-homeostasis. We show that erythritol effectively inhibited growth and progression of asexual blood stage malaria parasite by suppressing invasion and egress processes. It inhibited the liver stage (sporozoites) and transmission stage parasite (gametocytes) development that suggest its multi-stage, transmission-blocking potential. Interestingly, erythritol inhibited in vivo growth of malaria parasite in mouse experimental model. It was more effective in inhibiting parasite growth both in vivo and in vitro when tested together with a known anti-malarial artesunate. No Evans blue staining in treated mice indicated erythritol mediated protection of blood-brain barrier integrity in mice infected with P. berghei. Additionally, erythritol showed cytokine-modulating effect which suggest its direct effect on the host immune system. Our results of cellular thermal shift assay and ammonia detection assay demonstrate that erythritol binds with PfAQP and reduce the amount of ammonia release across the parasite respectively. We performed functional complementation assays which suggest that PfAQP expression in yeast mutant restores its growth in hyperosmotic conditions but showed reduced growth in the presence of erythritol, suggesting erythritol as an inhibitor of PfAQP. Overall, our data bestow erythritol as a promising new lead compound with an attractive antimalarial profile and could possibly be combined with known drugs without losing its efficacy.

molecular biology↗

bioRxiv2018

Cholesterol bound Plasmodium falciparum co-chaperone ‘PFA0660w’ complexes with major virulence factor ‘PfEMP1’ via chaperone ‘PfHsp70-x’

Lethality of Plasmodium falciparum (Pf) caused malaria results from cytoadherence, which is effected by exported Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family. Several exported Pf proteins (exportome) including chaperones alongside cholesterol rich microdomains are crucial for PfEMP1 translocation to infected erythrocyte surface. An exported Hsp40 (heat shock protein 40) PFA0660w functions as a co-chaperone of PfHsp70-x, and these co-localize to specialized intracellular mobile structures termed J-dots. Our studies attempt to understand the function of PFA0660w-PfHsp70-x chaperone pair using recombinant proteins. Biochemical assays reveal that N and C-terminal domains of PFA0660w and PfHsp70-x respectively are critical for their activity. We show the novel direct interaction of PfHsp70-x with the cytoplasmic tail of PfEMP1, and binding of PFA0660w with cholesterol. PFA0660w operates both as a chaperone and lipid binding molecule via its separate substrate and cholesterol binding sites. PfHsp70-x binds cholesterol linked PFA0660w and PfEMP1 simultaneously in vitro to form a complex. Collectively, our results and the past literature support the hypothesis that PFA0660w-PfHsp70-x chaperone pair assists PfEMP1 transport across the host erythrocyte through cholesterol containing J-dots. Since PFA0660w seems essential for parasite survival, characterization of its interaction with PfHsp70-x and J-dots may form the basis for development of future antimalarials.

molecular biology↗

bioRxiv2018

Structural insights into the binding mechanism of Plasmodium falciparum exported Hsp40-Hsp70 chaperone pair

Expression of heat shock proteins in Plasmodium falciparum (Pf) increases during febrile episodes to play key roles in several necessary cellular processes. PFA0660w-PfHsp70-x, an exported chaperone pair is known to co-localize to specialized intracellular structures termed J-dots, and has been implicated in trafficking of the major virulence factor, PfEMP1 (Plasmodium falciparum erythrocyte membrane protein 1) across the host cell. This article highlights for the first time detailed structural analysis of PFA0660w-PfHsp70-x chaperone pair to better understand their binding mechanism. Here, we have modeled reliable molecular structures for the complete conserved region of PFA0660w and PfHsp70-x. These structures were evaluated by different structure verification tools followed by molecular dynamics (MD) simulations. The model of PFA0660w was subjected to docking with PfHsp70-x using Haddock to reveal a number of residues crucial for their bipartite interaction, and also performed MD simulations on the complex. The peptide binding clefts of PFA0660w and its other Plasmodium species homologs were found to be bigger than their counterparts in higher eukaryotes like yeast, humans and C. parvum. Based on our results, we propose a model for PFA0660w-PfHsp70-x interaction and a mechanism of substrate binding, and compare it with its dimeric human counterparts. Owing to these striking structural differences between the host and parasite chaperones, such information on the essential Hsp40 and its partner Hsp70 may form the basis for rational drug design against fatal malaria.

bioinformatics↗