Danish is a postdoctoral research associate at the Brandman and Rohatgi groups at the Dept. of Biochemistry. His research focuses on understanding the mechanism of eukaryotic protein quality control pathways. Before joining Stanford, Danish earned his PhD from Texas A&M University, College Station, TX where he studied chemical inhibition of a lipid signaling protein and discovered a novel heme-binding lipid transfer protein. He also holds a Masters degree in Biotechnology from Banaras Hindu University in India, and a Bachelors degree from Presidency College, Kolkata (University of Calcutta), India. In addition to science, he likes to read about law and intersection of law and technology.
Honors & Awards
Dean's Fellowship, Stanford University (August, 2020)
Doctor of Philosophy, Texas A&M University College Station (2018)
Master of Science, Banaras Hindu University (2013)
Bachelor of Science, University Of Calcutta (2010)
A Sec14-like phosphatidylinositol transfer protein paralog defines a novel class of heme-binding proteins
Yeast Sfh5 is an unusual member of the Sec14-like phosphatidylinositol transfer protein (PITP) family. Whereas PITPs are defined by their abilities to transfer phosphatidylinositol between membranes in vitro, and to stimulate phosphoinositide signaling in vivo, Sfh5 does not exhibit these activities. Rather, Sfh5 is a redox-active penta-coordinate high spin FeIII hemoprotein with an unusual heme-binding arrangement that involves a co-axial tyrosine/histidine coordination strategy and a complex electronic structure connecting the open shell iron d-orbitals with three aromatic ring systems. That Sfh5 is not a PITP is supported by demonstrations that heme is not a readily exchangeable ligand, and that phosphatidylinositol-exchange activity is resuscitated in heme binding-deficient Sfh5 mutants. The collective data identify Sfh5 as the prototype of a new class of fungal hemoproteins, and emphasize the versatility of the Sec14-fold as scaffold for translating the binding of chemically distinct ligands to the control of diverse sets of cellular activities.
View details for DOI 10.7554/eLife.57081
View details for Web of Science ID 000567780500001
View details for PubMedID 32780017
View details for PubMedCentralID PMC7462610
Biophysical Parameters of the Sec14 Phospholipid Exchange Cycle
2019; 116 (1): 92–103
Sec14, the major yeast phosphatidylcholine (PC)/phosphatidylinositol (PI) transfer protein (PITP), coordinates PC and PI metabolism to facilitate an appropriate and essential lipid signaling environment for membrane trafficking from trans-Golgi membranes. The Sec14 PI/PC exchange cycle is essential for its essential biological activity, but fundamental aspects of how this PITP executes its lipid transfer cycle remain unknown. To address some of these outstanding issues, we applied time-resolved small-angle neutron scattering for the determination of protein-mediated intervesicular movement of deuterated and hydrogenated phospholipids in vitro. Quantitative analysis by small-angle neutron scattering revealed that Sec14 PI- and PC-exchange activities were sensitive to both the lipid composition and curvature of membranes. Moreover, we report that these two parameters regulate lipid exchange activity via distinct mechanisms. Increased membrane curvature promoted both membrane binding and lipid exchange properties of Sec14, indicating that this PITP preferentially acts on the membrane site with a convexly curved face. This biophysical property likely constitutes part of a mechanism by which spatial specificity of Sec14 function is determined in cells. Finally, wild-type Sec14, but not a mixture of Sec14 proteins specifically deficient in either PC- or PI-binding activity, was able to effect a net transfer of PI or PC down opposing concentration gradients in vitro.
View details for DOI 10.1016/j.bpj.2018.11.3131
View details for Web of Science ID 000455089100012
View details for PubMedID 30580923
View details for PubMedCentralID PMC6342728
Target Identification and Mechanism of Action of Picolinamide and Benzamide Chemotypes with Antifungal Properties
CELL CHEMICAL BIOLOGY
2018; 25 (3): 279-+
Invasive fungal infections are accompanied by high mortality rates that range up to 90%. At present, only three different compound classes are available for use in the clinic, and these often suffer from low bioavailability, toxicity, and drug resistance. These issues emphasize an urgent need for novel antifungal agents. Herein, we report the identification of chemically versatile benzamide and picolinamide scaffolds with antifungal properties. Chemogenomic profiling and biochemical assays with purified protein identified Sec14p, the major phosphatidylinositol/phosphatidylcholine transfer protein in Saccharomyces cerevisiae, as the sole essential target for these compounds. A functional variomics screen identified resistance-conferring residues that localized to the lipid-binding pocket of Sec14p. Determination of the X-ray co-crystal structure of a Sec14p-compound complex confirmed binding in this cavity and rationalized both the resistance-conferring residues and the observed structure-activity relationships. Taken together, these findings open new avenues for rational compound optimization and development of novel antifungal agents.
View details for DOI 10.1016/j.chembiol.2017.12.007
View details for Web of Science ID 000427600400008
View details for PubMedID 29307839
View details for PubMedCentralID PMC5856591
Structural elements that govern Sec14-like PITP sensitivities to potent small molecule inhibitors
JOURNAL OF LIPID RESEARCH
2016; 57 (4): 650–62
Sec14-like phosphatidylinositol transfer proteins (PITPs) play important biological functions in integrating multiple aspects of intracellular lipid metabolism with phosphatidylinositol-4-phosphate signaling. As such, these proteins offer new opportunities for highly selective chemical interference with specific phosphoinositide pathways in cells. The first and best characterized small molecule inhibitors of the yeast PITP, Sec14, are nitrophenyl(4-(2-methoxyphenyl)piperazin-1-yl)methanones (NPPMs), and a hallmark feature of NPPMs is their exquisite targeting specificities for Sec14 relative to other closely related Sec14-like PITPs. Our present understanding of Sec14::NPPM binding interactions is based on computational docking and rational loss-of-function approaches. While those approaches have been informative, we still lack an adequate understanding of the basis for the high selectivity of NPPMs among closely related Sec14-like PITPs. Herein, we describe a Sec14 motif, which we term the VV signature, that contributes significantly to the NPPM sensitivity/resistance of Sec14-like phosphatidylinositol (PtdIns)/phosphatidylcholine (PtdCho) transfer proteins. The data not only reveal previously unappreciated determinants that govern Sec14-like PITP sensitivities to NPPMs, but enable predictions of which Sec14-like PtdIns/PtdCho transfer proteins are likely to be NPPM resistant or sensitive based on primary sequence considerations. Finally, the data provide independent evidence in support of previous studies highlighting the importance of Sec14 residue Ser173 in the mechanism by which NPPMs engage and inhibit Sec14-like PITPs.
View details for DOI 10.1194/jlr.M066381
View details for Web of Science ID 000373924600014
View details for PubMedID 26921357
View details for PubMedCentralID PMC4808773
Phosphatidylinositol transfer proteins and instructive regulation of lipid kinase biology
BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR AND CELL BIOLOGY OF LIPIDS
2015; 1851 (6): 724–35
Phosphatidylinositol is a metabolic precursor of phosphoinositides and soluble inositol phosphates. Both sets of molecules represent versatile intracellular chemical signals in eukaryotes. While much effort has been invested in understanding the enzymes that produce and consume these molecules, central aspects for how phosphoinositide production is controlled and functionally partitioned remain unresolved and largely unappreciated. It is in this regard that phosphatidylinositol (PtdIns) transfer proteins (PITPs) are emerging as central regulators of the functional channeling of phosphoinositide pools produced on demand for specific signaling purposes. The physiological significance of these proteins is amply demonstrated by the consequences that accompany deficits in individual PITPs. Although the biological problem is fascinating, and of direct relevance to disease, PITPs remain largely uncharacterized. Herein, we discuss our perspectives regarding what is known about how PITPs work as molecules, and highlight progress in our understanding of how PITPs are integrated into cellular physiology. This article is part of a Special Issue entitled Phosphoinositides.
View details for DOI 10.1016/j.bbalip.2014.12.011
View details for Web of Science ID 000353095800004
View details for PubMedID 25592381
View details for PubMedCentralID PMC5221696