Member, Maternal & Child Health Research Institute (MCHRI)
Honors & Awards
MCHRI Postdoctoral Fellow, Stanford Maternal and Child Health Research Institute (2020-2022)
Dean's Postdoctoral Fellow, Stanford University School of Medicine (2020)
Ph.D., National Centre for Biological Sciences, India, Biochemistry and Biophysics (2018)
M.Sc., University of Delhi, India, Biochemistry (2009)
B.Sc., University of Delhi, India, Biochemistry (2007)
James Spudich, Postdoctoral Faculty Sponsor
Nanomechanical Phenotypes in Cardiac Myosin-Binding Protein C Mutants That Cause Hypertrophic Cardiomyopathy.
Hypertrophic cardiomyopathy (HCM) is a disease of the myocardium caused by mutations in sarcomeric proteins with mechanical roles, such as the molecular motor myosin. Around half of the HCM-causing genetic variants target contraction modulator cardiac myosin-binding protein C (cMyBP-C), although the underlying pathogenic mechanisms remain unclear since many of these mutations cause no alterations in protein structure and stability. As an alternative pathomechanism, here we have examined whether pathogenic mutations perturb the nanomechanics of cMyBP-C, which would compromise its modulatory mechanical tethers across sliding actomyosin filaments. Using single-molecule atomic force spectroscopy, we have quantified mechanical folding and unfolding transitions in cMyBP-C domains targeted by HCM mutations that do not induce RNA splicing alterations or protein thermodynamic destabilization. Our results show that domains containing mutation R495W are mechanically weaker than wild-type at forces below 40 pN and that R502Q mutant domains fold faster than wild-type. None of these alterations are found in control, nonpathogenic variants, suggesting that nanomechanical phenotypes induced by pathogenic cMyBP-C mutations contribute to HCM development. We propose that mutation-induced nanomechanical alterations may be common in mechanical proteins involved in human pathologies.
View details for DOI 10.1021/acsnano.1c02242
View details for PubMedID 34060810
Study of Hcm Causing beta-Cardiac Myosin Mutations Located at Different Structurally Significant Regions of the Myosin-Head
CELL PRESS. 2020: 435A
View details for Web of Science ID 000513023202668
Uncovering the Molecular and Structural Basis of Hypertrophic Cardiomyopathy-Causing Mutations in Myosin and Myosin Binding Protein-C
CELL PRESS. 2020: 435A
View details for Web of Science ID 000513023202667
A five-residue motif for the design of domain swapping in proteins
2019; 10: 452
Domain swapping is the process by which identical monomeric proteins exchange structural elements to generate dimers/oligomers. Although engineered domain swapping is a compelling strategy for protein assembly, its application has been limited due to the lack of simple and reliable design approaches. Here, we demonstrate that the hydrophobic five-residue 'cystatin motif' (QVVAG) from the domain-swapping protein Stefin B, when engineered into a solvent-exposed, tight surface loop between two β-strands prevents the loop from folding back upon itself, and drives domain swapping in non-domain-swapping proteins. High-resolution structural studies demonstrate that engineering the QVVAG stretch independently into various surface loops of four structurally distinct non-domain-swapping proteins enabled the design of different modes of domain swapping in these proteins, including single, double and open-ended domain swapping. These results suggest that the introduction of the QVVAG motif can be used as a mutational approach for engineering domain swapping in diverse β-hairpin proteins.
View details for DOI 10.1038/s41467-019-08295-x
View details for Web of Science ID 000456828100001
View details for PubMedID 30692525
View details for PubMedCentralID PMC6349918
Amino-acid composition after loop deletion drives domain swapping
2017; 26 (10): 1994–2002
Rational engineering of a protein to enable domain swapping requires an understanding of the sequence, structural and energetic factors that favor the domain-swapped oligomer over the monomer. While it is known that the deletion of loops between β-strands can promote domain swapping, the spliced sequence at the position of the loop deletion is thought to have a minimal role to play in such domain swapping. Here, two loop-deletion mutants of the non-domain-swapping protein monellin, frame-shifted by a single residue, were designed. Although the spliced sequence in the two mutants differed by only one residue at the site of the deletion, only one of them (YEIKG) promoted domain swapping. The mutant containing the spliced sequence YENKG was entirely monomeric. This new understanding that the domain swapping propensity after loop deletion may depend critically on the chemical composition of the shortened loop will facilitate the rational design of domain swapping.
View details for DOI 10.1002/pro.3237
View details for Web of Science ID 000411179200009
View details for PubMedID 28710790
View details for PubMedCentralID PMC5606538
Rapidly fatal myeloproliferative disorders in mice with deletion of Casitas B-cell lymphoma (Cbl) and Cbl-b in hematopoietic stem cells
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2010; 107 (37): 16274–79
Casitas B-cell lymphoma (Cbl)-family E3 ubiquitin ligases are negative regulators of tyrosine kinase signaling. Recent work has revealed a critical role of Cbl in the maintenance of hematopoietic stem cell (HSC) homeostasis, and mutations in CBL have been identified in myeloid malignancies. Here we show that, in contrast to Cbl or Cbl-b single-deficient mice, concurrent loss of Cbl and Cbl-b in the HSC compartment leads to an early-onset lethal myeloproliferative disease in mice. Cbl, Cbl-b double-deficient bone marrow cells are hypersensitive to cytokines, and show altered biochemical response to thrombopoietin. Thus, Cbl and Cbl-b play redundant but essential roles in HSC regulation, whose breakdown leads to hematological abnormalities that phenocopy crucial aspects of mutant Cbl-driven human myeloid malignancies.
View details for DOI 10.1073/pnas.1007575107
View details for Web of Science ID 000281799000055
View details for PubMedID 20805496
View details for PubMedCentralID PMC2941297
Reciprocal Regulation of AKT and MAP Kinase Dictates Virus-Host Cell Fusion
JOURNAL OF VIROLOGY
2010; 84 (9): 4366-4382
Viruses of the Paramyxoviridae family bind to their host cells by using hemagglutinin-neuraminidase (HN), which enhances fusion protein (F)-mediated membrane fusion. Although respiratory syncytial virus and parainfluenza virus 5 of this family are suggested to trigger host cell signaling during infection, the virus-induced intracellular signals dictating virus-cell fusion await elucidation. Using an F- or HN-F-containing reconstituted envelope of Sendai virus, another paramyxovirus, we revealed the role and regulation of AKT1 and Raf/MEK/ERK cascades during viral fusion with liver cells. Our observation that extracellular signal-regulated kinase (ERK) activation promotes viral fusion via ezrin-mediated cytoskeletal rearrangements, whereas AKT1 attenuates fusion by promoting phosphorylation of F protein, indicates a counteractive regulation of viral fusion by reciprocal activation of AKT1 and mitogen-activated protein kinase (MAPK) cascades, establishing a novel conceptual framework for a therapeutic strategy.
View details for DOI 10.1128/JVI.01940-09
View details for Web of Science ID 000276358000024
View details for PubMedID 20164223
View details for PubMedCentralID PMC2863742