Molecular and Cellular Biology; RNA; Virology
My research is dedicated to the folding of biological macromolecules such as ribonucleic acids and proteins into higher-order structures and to the role their conformation plays in the way they exert their function within the cell. In particular, my research group studies RNA structural switches involved in the replication of RNA viruses and subviral RNA pathogens. We also study RNA and protein structures that contribute to the regulation of gene expression in other microbial systems through specific RNA-RNA and RNA-protein interactions. Plus-strand RNA viruses are responsible for many diseases in humans, animals and plants. Our efforts are focused on an early step in the viral life cycle within the host cell, the recruitment of the viral RNA genome into a replication complex with viral and cellular proteins. We use yeast as a model host to express two RNA replicons, turnip crinkle virus associated with satellite RNA, by itself or in the presence of viral replication proteins, and potato spindle tuber viroid RNA. Satellites and viroids are subviral RNAs that do not encode their own proteins; they rely entirely on factors provided by the associated helper virus or the host cell. The smaller size and simpler organization of their genome makes them convenient model systems to investigate the role of RNA structure in recognition by viral and host proteins, structural changes involved in these interactions, molecular evolution and intracellular transport. Our goal is to develop a fully controlled replication system where every component is tractable and tunable using tools from genetics, biochemistry, cellular and molecular biology. With this system, we will be able to screen for RNA replication inhibitors and develop RNA vectors with novel functions. I enjoy teaching and mentoring students from a variety of disciplines in the laboratory as well as in the classroom. I believe that meaningful faculty/student interaction is mutually beneficial: it helps students grow into well-rounded citizen-scientists, researchers or health care professionals, and it helps me become a better educator. In my research group, I deeply value and strive to foster diversity. I believe a diverse team creates a more energizing and successful research environment--one where everyone learns from one another and the range of backgrounds and perspectives adds up to a rich learning environment that is much more than the sum of its parts. I am the course director for, and teach in Microbiology for Allied Health Professionals. On the graduate level, I direct the master’s program and teach in the core course of virology.
Apoptosis and cell death; Bioinformatics; Endocrinology; Gene Expression; Gene therapy; Genomics and proteomics; Immunology; Molecular Basis of Disease; Molecular and Cellular Biology; Neurobiology; RNA; Viral Pathogenesis
Dr. Mahajan has established herself as an investigator in the area of neuropathogenesis of HIV-1 in the context of drug abuse. She has initiated several new projects that investigate the role of a unique key signaling molecule in the dopaminergic pathway that impacts drug addiction, depression and other neurological disorders. Her focus has always been on collaborative, interdisciplinary partnerships between various Departments within UB that include the Institute of Lasers, Photonics and Biophotonics, Research Institute of Addiction, Dept of Computer Science and Engineering, Dept of Pharmaceutical sciences and the Department of Bioengineering. This inclusive strategy has facilitated the emergence of a robust, innovative clinical translational research program for our Division that continues to grow steadily. Dr Mahajan has obtained independent research funding from NIDA, the pharmaceutical Pfizer, US- Fulbright and other Private Foundations such as Dr. Louis Skalrow Memorial trust to conduct some of these research projects. Dr. Mahajan is Director of Research of the Division of Allergy, Immunology & Rheumatology. She supervises the research training of the Allergy fellows,Medical residents, graduate and undergraduate students. Dr. Mahajan has presented her research work at National and International conferences and was an invited speaker at several seminars and colloquiums. She has authored over 95 publications in several top quality peer reviewed journals and has thus demonstrated a high level of scholarly productivity. She is a reviewer and an adhoc member of the editorial board of several journals in her field. The following is a brief synopsis of her research interests. HIV neuropathogenesis in the context of drug abuse: We proposed that Opiates act as co-factors in the pathogenesis of HIV-1 infections by directly suppressing immune functions of the host through interactions with mu-opioid receptors on lymphocytes. Exacerbation of HIV encephalopathy (HIVE) is observed with opiate abuse. The mechanisms underlying HIVE are currently undetermined however, they likely to include the generation of endogenous neurotoxins combined, perhaps synergistically, with bioreactive HIV-1 envelope proteins. We believe that these proposed mechanisms may work through a common signal transduction mechanism activating dopamine D1 receptors in the nucleus accumbens of the brain. Opiate abuse by HIV-1 infected subjects may exacerbate the progression of HIVE as a consequence of the combined effects of HIV-1 induced neurotoxins plus opiate induced increases in the D1 receptor activation. We hypothesize that the dopaminergic signaling pathway is the central molecular mechanism that integrates the neuropathogenic activities of both HIV-1 infections and the abuse of opiate drugs. In this context our investigation is focused on the DARPP-32 signalling pathway. Addictive drugs act on the dopaminergic system of the brain and perturb the function of the dopamine- and cyclic-AMP-regulated phosphoprotein of molecular weight 32 kD (DARPP-32). DARPP-32 is critical to the pathogenesis of drug addiction by modulating both transcriptional and post-translational events in different regions of the brain. DARPP-32 is localized within neurons containing dopamine receptors and is a potent inhibitor of another key molecule in the dopaminergic signaling pathway, protein phosphatase 1 (PP-1). We propose that the sustained silencing of DARPP-32 gene expression using specific siRNA delivered to the brain is an innovative approach for the treatment of drug addiction. The specific challenge of the proposed project is the non-invasive delivery of biologically stable, therapeutic siRNA molecules to target cells within the brain. We are developing biocompatible nanoparticles to both protect DARPP-32 specific siRNA against degradation and deliver it from the systemic circulation across the BBB to specific dopaminergic neurons in the brain of patients with opiate addictions. BBB Research: While examining neuropathogenesis of HIV, we became interested in the role of the blood-brain barrier (BBB) in HIV neuropathogenesis with the objective of developing therapeutic interventions to prevent and limit the progression of HIV associated neurological disease. The blood-brain barrier is an intricate cellular system composed of vascular endothelial cells and perivascular astrocytes that restrict the passage of molecules between the blood stream and the brain parenchyma. We evaluated and validated both the 2 and 3 dimensional human in-vitro BBB models in my laboratory, that allowed examining permeability of virus, effects of drugs of abuse on BBB permeability, mechanisms of BBB transport, and tight junction modulation. Our goal remains to determine the impact of current and potential CNS antiretrovirals, psychopharmacologic, and other medications on the integrity of the BBB in HIV associated neurological disorder and other neurodegenerative diseases. Additionally, We also investigate mechanisms that underlie drugs of abuse induced neuronal apoptosis. Systems biology approach: We expanded our investigation to include functional genomic/proteomic analyses that allowed characterization of gene/ protein modulation in response to a drug stimulus or under a specific disease condition. We developed an expertise in these large-scale genomic and proteomic studies and the genomic studies helped identify key genes that underlie molecular mechanisms in drug addiction, HIV diseases progression, and allowed examination of the interplay of genes and environmental factors. The proteomic studies confirmed the presence of specific proteins that regulate key biological processes in drug addiction and HIV diseases progression. Recently, We have expanded my research program to include microbiome analyses and incorporated the utility of the computational drug discovery platform (CANDO) model that allows studying interaction between protein structures from microbiome genomes and determine the interactions that occur between them and small molecules (drugs and human/bacterial metabolites that are already a part of or continue to be added to the CANDO library. Using the CANDO Platform we are able to do the hierarchical fragment-based docking with dynamics between those compounds/drugs and the microbiome proteins/proteomes to determine which ones of the drugs and metabolites will work most efficaciously in patients using specific drugs. NanoMedicine: Over the last couple of years, We have become increasingly interested in nanomedicine and have developed several interdisciplinary clinical translational research focused collaborations that include 1) Nanotechnology based delivery systems to examine antitretroviral transport across the BBB; 2) Nanotherapeutics using siRNA/Plasmid delivery to specific regions in the brain to target various genes of interest specifically those pertaining to the dopaminergic pathway that includes a phosphor protein called “DARPP-32”. Targeting various key genes in the dopaminergic pathway results in the modulation of behavioral response which we observed in animal models of addiction/depression, 3) Biodistribution studies of various nanotherapeutic formulations using PET small animal imaging. Additionally, We are also focused on exploring epigenetic mechanisms that under drug addiction and mechanisms that underlie oxidative stress in neurodegenerative diseases.
Eukaryotic Pathogenesis; Gene Expression; Infectious Disease; Microbial Pathogenesis; Microbiology; RNA; Signal Transduction
There are estimated to be over one million species of fungi on the earth, yet very few of these species are capable of causing deadly systemic infections in humans. One of the major limiting factors for most fungi is their inability to grow at mammalian core body temperature. We utilize the fungal pathogen Cryptococcus neoformans var. grubii as a representative fungal pathogen to understand how these few fungi have adapted to growth at mammalian body temperature. C. neoformans is a worthy pathogen, as it is estimated to cause over 500,000 deaths from meningoencephalitis per year, primarily in Africa and Southeast Asia as an HIV/AIDS comorbidity. We use the temperature-limited Cryptococcus amylolentus as a comparator; it is an environmental strain that produces similar virulence factors to C. neoformans and is fully virulent in surrogate invertebrate hosts at permissive temperatures. We have discovered that host temperature adaptation in C. neoformans is accompanied by a reprogramming of gene expression at the level of messenger RNA (mRNA) stability. In response to temperature stress, C. neoformans rapidly degrades mRNAs that encode energy consuming machinery such as ribosomes. At the same time, it prioritizes the translation of stress-responsive mRNAs on existing ribosomes. Because mRNA synthesis and decay are coupled processes, we seek to identify the protein components of mRNA complexes that mediate the specificity of this decay process and posttranslational modifications, such as arginine methylation and phosphorylation, that modify their function. In addition, we are investigating the signaling pathways that accelerate or slow mRNA decay in response to specific environmental stimuli such as host temperature and nutrient deprivation. Finally, mRNA decay not only alters gene expression at the posttranscriptional level, but the degradation of abundant mRNAs during stress releases nucleotide intermediates that can be utilized by the stressed cell to promote genome stability. We are investigating the process of mRNA degradation as well as nucleotide metabolic pathways as drug targets in C. neoformans and other fungal pathogens. Our goal is to define the unique attributes of C. neoformans that confer pathogenicity and to identify potential targets for novel therapeutics. Each of my students has a project that contributes to the overall goals of my research team. Students in my laboratory work independently, though with frequent interaction with me regarding the direction of investigation and interpretation of data. Regular meetings allow us to provide input on each other’s projects. I expect my students to present their work at least once per year at a national or international meeting, and I expect them to do the bulk of the work in writing papers describing their findings for publication.
Eukaryotic Pathogenesis; Gene Expression; Genomics and proteomics; Infectious Disease; Microbial Pathogenesis; Microbiology; Molecular and Cellular Biology; Molecular genetics; Protein Function and Structure; RNA
Trypanosoma brucei is a eukaryotic pathogen that causes human African trypanosomiasis, a disease that is invariably fatal if not treated. Essential and novel processes in this parasite may serve as starting platforms for new chemotherapeutics, which are urgently needed. Our laboratory combines biochemical, genetic, genomic and proteomic approaches toward understanding gene regulation and protein modification in this pathogenic eukaryote. One focus in my laboratory is RNA editing, a novel mechanism for regulating mitochondrial gene expression in which sequence information is added to mRNAs after transcription by specific insertion and deletion of uridine residues. RNA editing is essential for creating translatable open reading frames (ORFs). We are performing functional and biochemical characterization of the large, dynamic RNA-protein complex termed MRB1, which coordinates multiple aspects of the RNA editing process. A second focus is on regulating RNA stability and translational control in T. brucei, which constitute the major methods of gene regulation in this organism. We identified an RNA binding protein, DRBD18, that impacts the stabilities of hundreds of mRNAs. Our data support a model in which posttranslational modification of DRBD18 by arginine methylation acts as a switch to change DRBD18 from an mRNA destabilizer to an mRNA stabilizer by regulating specific protein-protein and protein-RNA interactions. We are testing this model in vitro and in vivo using reporter assays, in vivo protein-RNA cross-linking and protein-protein interaction assays. A third focus is on understanding the mechanisms by which protein arginine methylation modulates trypanosome biology. We performed a global proteomic analysis of the arginine methylome of T. brucei, identifying >1100 methylproteins spanning most cellular compartments and a wide array of functional classes. We are now analyzing novel mechanisms of protein arginine methyltransferase regulation and defining the physiological and molecular functions of arginine methylmarks on selected proteins. I foster a collaborative and flexible laboratory environment, and I encourage my students to explore the research topics that interest them.
Cell growth, differentiation and development; Membrane Transport (Ion Transport); Molecular and Cellular Biology; Signal Transduction; Inherited Metabolic Disorders; RNA
Regulation of Kidney Epithelial Cell Growth, Transport and Differentiation Our laboratory is investigating the molecular mechanisms by which hormones, growth factors and extracellular matrix proteins regulate kidney tubule epithelial cell growth and functional differentiation in vitro. An established canine kidney epithelial cell line, MDCK, and isolated "mutants" are currently being utilized to examine the actions of growth regulatory on the expression of several proteins including the Na+, K+-ATPase and laminin, a glycoprotein in the extracellular matrix. The effects of novel growth regulatory factors on the expression of proteins involved in gluconeogenesis, membrane transport, renal disease and growth control in primary renal cell cultures are being examined. Primary kidney epithelial cells differentiate into nephrons in a reconstituted extracellular matrix proteins is the subject of study.
Infectious Disease; Microbiology; Microbial Pathogenesis; Molecular and Cellular Biology; Gene Expression; Transcription and Translation; Protein Function and Structure; RNA; Eukaryotic Pathogenesis
In my laboratory, we use molecular biological and biochemical approaches to study Trypanosoma brucei, the causative agent of African sleeping sickness, and Trypanosoma cruzi, which causes Chagas disease in South and Central America. Treatment for these diseases is severely limited due to increasing drug resistance and lack of available drugs. The goal of our work is to discover and exploit critical events that occur in the parasite life cycle that may be used to prevent growth or transmission of the parasite. The major project in my laboratory examines the ribosome, the complex molecular machine that drives protein synthesis. While many features of the ribosome and its assembly pathway are conserved in the parasites we study, we have identified features that are very different from the human host. Our laboratory discovered a pair of trypanosome-specific RNA binding proteins, P34 and P37, that are part of a unique preribosomal complex that is essential for ribosomal biogenesis and survival of trypanosomes. This may suggest that the interaction of these proteins with other components of the ribosomal assembly pathway can be developed as targets for chemotherapy. We are developing a high-throughput screen for small molecules that disrupt the complex in trypanosomes and do not harm the human host. My team and I also collaborate with Dr. Joachim Frank at Columbia University on a project to examine the structure of the ribosome and intermediates in the pathway of assembly using cryo-electron microscopy (cryo-EM). These experiments will provide important information about the unique features of the structure and function of the trypanosome ribosome and further our discovery of potential drug targets. In addition, we continue in a long-standing collaboration with Dr. Beatriz Garat at the Universidad de la Républica in Uruguay, examining both DNA and RNA binding proteins which regulate gene expression in Trypanosoma cruzi. The balance of graduate, undergraduate and medical students and postdoctoral researchers I mentor changes from year to year, though the international quality I strive to maintain has distinguished my laboratory for years: I enjoy having students from around the world as part of my research team. I am the course director for, and lecture in Critical Analysis and Eukaryotic Pathogens. I am also the course director for Eukaryotic Gene Expression and the co-course director for Molecular Parasitology. Additionally, I lecture in Microbiology for Undergraduates.