Biology subjects

Pundir, P.

Publications and source records attributed to Pundir, P..

3 recordsLinked to original sources

bioRxiv2025

The neuroendocrine peptide catestatin promotes clearance of cutaneous Staphylococcus aureus through mast cell Mrgpr activation

Methicillin-resistant Staphylococcus aureus (MRSA) is a leading cause of cutaneous infections, underscoring the need for alternative therapeutic strategies. Catestatin, a neuroendocrine antimicrobial peptide produced by neurons and epithelial cells, has been implicated in skin defense against pathogens such as MRSA, though its mechanisms remain unclear. Here, we show that catestatin expression is upregulated in MRSA-infected skin wounds and that topical catestatin application significantly reduces MRSA burden in infected murine cutaneous wounds. This effect is dependent on the mast cell-specific G protein-coupled receptor Mrgprb2, the murine ortholog of human MRGPRX2. Notably, catestatin treatment leads to Mrgprb2-dependent suppression of inflammatory cytokine production and leukocyte infiltration, alongside upregulation of the antimicrobial peptide Defb14. In human mast cells, catestatin induces MRGPRX2-dependent degranulation, histamine release, prostaglandin D2 production, and cytokine expression. Pharmacological inhibition and western blot analysis reveal that catestatin activates multiple downstream G protein-dependent signaling pathways in an MRGPRX2-dependent manner. These findings demonstrate that catestatin promotes bacterial clearance by activating mast cells through Mrgprb2, thereby enhancing antimicrobial peptide production. Our study positions catestatin as a promising mast cell-targeting immunotherapeutic candidate for treating antibiotic-resistant skin infections.

immunology↗

bioRxiv2025

Spatiotemporal dynamics of cryptococcal infection reveal novel immune modulatory mechanisms and antifungal targets

The threat and incidence of fungal diseases are increasing, as is the severity and mortality rates associated with these infections. New strategies to combat fungal infections are urgently needed to overcome rising rates of resistance and the emergence of new pathogens. To promote invasion within a host, fungi use highly adapted and regulated virulence factors, and, in turn, the host adopts an active and dynamic immune response to suppress infection. Understanding the interplay between these processes is crucial to move fungal disease management and treatment forward and improve global health outcomes. Within the present study, we tackle these challenges using state-of-the-art mass spectrometry instrumentation to explore proteome remodeling during active infection of Cryptococcus neoformans at an unprecedented depth with spatiotemporal resolution. Our prioritization of three host organs (i.e., lungs, brain, spleen) critical to initiation, progression, and response of disease discovers tissue-specific remodeling across time. Within the lungs, we revealed early and sustained activation of the host immune response integrated with characterization of a promising new antifungal target, and we propose the discovery of a competitive inhibitor for functional target disruption. Within the brain, proteome remodeling aligns with disease progression, and we define a new mechanistic role for haptoglobin in fungal cell modulation, as well as showcasing an adaptive survival response of C. neoformans within an hypoxic environment. Within the spleen, we reveal new dynamics of immune system activation upon cryptococcal infection. Overall, we provide the deepest integrated view of cryptococcal disease dynamics across temporal and spatial scales, revealing unrecognized mechanisms of host immunity and fungal pathogenesis that offer new avenues for targeted therapeutic intervention and disease management.

microbiology↗

bioRxiv2023

Plasmodium falciparum contains functional SCF and CRL4 ubiquitin E3 ligases, and CRL4 is critical for cell division and membrane integrity

Protein ubiquitination is essential for cellular homeostasis and regulation of several processes, including cell division and genome integrity. Ubiquitin E3 ligases determine substrate specificity for ubiquitination, and Cullin-RING ubiquitin E3 Ligases (CRLs) make the largest group among the ubiquitin E3 ligases. Although conserved and most studied in model eukaryotes, CRLs remain underappreciated in Plasmodium and related parasites. To investigate the CRLs of human malaria parasite Plasmodium falciparum, we generated parasites expressing tagged P. falciparum cullin-1 (PfCullin-1), cullin-2 (PfCullin-2), Rbx1 (PfRbx1) and Skp1 (PfSkp1). PfCullin-1 and PfCullin-2 were predominantly expressed in erythrocytic trophozoite and schizont stages, with nucleocytoplasmic localization and chromatin association, suggesting their roles in different cellular compartments and DNA-associated processes. Immunoprecipitation, in vitro protein-protein interaction and ubiquitination assay confirmed the presence of a functional SCF (PfSCF), comprising of PfCullin-1, PfRbx1, PfSkp1, PfFBXO1 and calcyclin binding protein. Immunoprecipitation, sequence analysis and ubiquitination assay indicated that PfCullin-2 forms a functional human CRL4-like complex (PfCRL4), consisting of PfRbx1, cleavage and polyadenylation specific factor subunit_A and WD40 repeat proteins. PfCullin-2 knock-down at the protein level, which would hinder PfCRL4 assembly, significantly decreased asexual and sexual erythrocytic stage development. Several pathways, including protein translation and folding, lipid biosynthesis and transport, DNA replication, and protein degradation were dysregulated upon PfCullin-2-depletion, which likely reflects association of PfCRL4 with multiple pathways. Consistent with dysregulation of multiple pathways, PfCullin-2-depleted schizonts had poorly delimited merozoites and internal membraned structures, suggesting a role of PfCRL4 in maintaining membrane integrity. PfCullin-2-depleted parasites had significantly lower number of nuclei/parasite than the normal parasites, indicating a crucial role of PfCRL4 in cell division. Taken together, we for the first time demonstrate the presence of functional CRLs in P. falciparum, with crucial roles for PfCRL4 in cell division and maintaining membrane integrity. This study will benefit investigation of similar ligases in related parasites.

microbiology↗