Manasi Sawant

All Publications

• Human cathelicidin peptide LL-37 compacts nucleic acids and alters neutrophil extracellular trap structure. Scientific reports Zielke, C., Rad, B., Nielsen, J. E., Li, J., Pimcharoen, S., Sawant, M., Kamayirese, S., Lin, J. S., Thiam, H. R., Barron, A. E. 2026

  Abstract

  The human cathelicidin host defense peptide LL-37 is expressed by many cell types, including neutrophils, macrophages, and epithelial cells, and forms complexes with nucleic acids that can have either beneficial or detrimental health effects. We suggest that these differential impacts are directly connected to the extent of nucleic acid binding by LL-37. Here, we use phage λ DNA and techniques such as high-resolution video microscopy, gel electrophoresis, circular dichroism, and displacement assays to show that LL-37 binds non-specifically to dsDNA, condensing it, followed by formation of progressively larger complexes from smaller domains, until "complete" complexation is attained at a (w/w) ratio of DNA/LL-37 of 1:1.7. The morphology of these complexes is concentration-dependent, with relatively low LL-37 amounts yielding loosely aggregated DNA structures and higher LL-37 concentrations leading to well-defined, disc-like complexes of about 150 nm in diameter. The condensation of nucleic acids, which causes a loss of the characteristic B-DNA features, results from interactions of the phosphodiester backbone with cationic amino acid side chains of the peptide at physiological pH, most likely in A-T rich sequences of the nucleic acid. Our results show that the α-helical structure of the peptide with its amphipathic and hydrophobic surfaces is essential. Finally, we show that LL-37 complexation alters the structure of neutrophil extracellular traps (NETs), causing a significant reduction in projected NET area at high LL-37 concentrations. Our data suggest that LL-37 helps prevent nucleic acid dispersal and condenses dsDNA, which may impact the biophysics of NET clearance.

  View details for DOI 10.1038/s41598-026-48091-4

  View details for PubMedID 42156793

• Investigation of Regulation and Binding Patterns of the Human Cathelicidin Peptide LL-37 in Complexation with Nucleic Acids, and its Impact on Neutrophil Extracellular Traps. bioRxiv : the preprint server for biology Zielke, C., Rad, B., Nielsen, J. E., Li, J., Pimcharoen, S., Sawant, M., Lin, J. S., Thiam, H. R., Barron, A. E. 2026

  Abstract

  The human cathelicidin host defense peptide LL-37 forms complexes with nucleic acids that can have either beneficial or detrimental health effects. We suggest that these differential impacts are directly connected to dsDNA binding by LL-37 and to complex formation between protomers. Here, we show using phage λ DNA that LL-37 binds non-specifically to dsDNA, condensing it, followed by complex formation between LL-37 peptides. We find that complex formation is concentration-dependent, with low LL-37 amounts yielding loosely aggregated DNA structures, while higher LL-37 concentrations lead to well-defined, disc-like structures of about 150 nm in diameter. The condensation of the nucleic acids, which causes a loss of the characteristic B-DNA features, results from interactions of the phosphodiester backbone with protonated amino acid side chains of the peptide at physiological pH, predominantly in A-T rich sequences of the nucleic acid. However, in our studies, electrostatic interactions did not appear to be the driving force for complexation, but rather we found the α-helical structure of the peptide with its amphipathic and hydrophobic surfaces to be essential. Further, we show that LL-37 also interacts with nucleic acids from neutrophil extracellular traps (NETs) in a concentration-dependent way, causing a reduction in NET aggregate area, which may offer new biophysical insights into diseases such as systemic lupus erythematosus (SLE), which involve slower-than-normal NET clearance. Our results indicate the key importance of LL-37 expression levels for regulation of the innate immune system for optimal human health, since the relative amounts of expressed LL-37 present to interact with extracellular DNA will determine the extent to which the DNA can be condensed, which in turn will affect the ability of the body to clear the NETs before they can cause inflammatory conditions.

  View details for DOI 10.64898/2026.02.09.704888

  View details for PubMedID 41727055

  View details for PubMedCentralID PMC12918999

• Autoantibody hotspots reveal the origin and impact of immunogenic XIST ribonucleoprotein complexes in autoimmune diseases. The Journal of clinical investigation Yan, B., Lee, J., Srinivasan, S., Ambriz, P., Shi, Q., Dou, D. R., Davuluri, S., Nandyala, S., Woods, A., Leatherman, G., Zhao, Y., Reggiardo, R. E., Sawant, M., Thiam, H. R., Shah, A. A., Fiorentino, D. F., Chung, L. S., Chang, H. Y. 2026

  View details for DOI 10.1172/JCI198291

  View details for PubMedID 41665934

• Autoantibody hotspots reveal origin and impact of immunogenic XIST ribonucleoprotein complex. bioRxiv : the preprint server for biology Yan, B., Lee, J., Srinivasan, S., Shi, Q., Dou, D. R., Davuluri, S., Nandyala, S., Woods, A., Leatherman, G., Zhao, Y., Reggiardo, R. E., Sawant, M., Thiam, H. R., Shah, A. A., Fiorentino, D. F., Chung, L. S., Chang, H. Y. 2025

  Abstract

  Four out of five patients with autoimmune diseases are women. The XIST ribonucleoprotein (RNP) complex, comprising the female-specific long noncoding RNA XIST and over 100 associated proteins, may drive several autoimmune diseases that disproportionately affect women, who have elevated levels of autoantibodies against the XIST RNP. However, the structural distribution, potential origin, and clinical significance of XIST RNP autoantibodies remained unexplored. Here, we find that XIST RNP is associated with autoantigens associated with six female-biased autoimmune conditions. Mapping autoantibody targets to their occupancy sites on XIST shows that these autoantigens are concentrated at discrete "hotspots" along the XIST lncRNA, notably the A-repeat. Cell type-specific protein expression data nominated neutrophils as a predominant source of hotspot antigens, and we confirmed the presence of both XIST and hotspot antigens in neutrophil extracellular traps during NETosis, an immunogenic programmed cell death pathway triggered by neutrophil activation upon which neutrophils extrude their nuclear content. Furthermore, we found that levels of autoantibodies against a top hotspot antigen, SPEN, that binds the A-repeat, correlate with severe digital ischemia in systemic sclerosis in two independent cohorts. Together, these data show a plausible mechanism for the origin of AXA, guided by RNA structure and RNA-protein interactions, and show that antibodies to XIST RNP holds promise for disease endotyping and prognostication in female-biased autoimmune conditions.Novel autoantibodies target hotspots on XIST ribonucleoprotein complex in female-biased autoimmune diseases.

  View details for DOI 10.1101/2025.01.16.633465

  View details for PubMedID 39896599

  View details for PubMedCentralID PMC11785099