Amit Bhavsar

portrait of Amit Bhasvar

Adjunct Assistant Professor
Department of Medical Microbiology and Immunology

 


Research Overview:
There are two main research areas in the Bhavsar lab. We are very interested in understanding what bacterial effector proteins do when they get into their hosts. Questions such as how effectors recognize their host substrates, and how their actions subvert host processes keep us pondering these fascinating scenarios. We are also very interested in how we can improve the safety of childhood cancer treatments so that we can preserve the use of highly effective chemotherapies, while preventing serious treatment-related toxicities for survivors.

Functional pharmacogenomics of chemotherapy-related adverse drug reactions

Overview: Improvements in childhood cancer survival rates have unfortunately been accompanied by the recognition that these treatments can lead to severe toxicities in survivors. Our lab is studying hearing loss in children that has arisen as a consequence of receiving cancer chemotherapy treatment. This research will build upon a new genetic discovery that has identified an immune signaling pathway that contributes to the development of hearing loss to the drug cisplatin. We will confirm this discovery by genetically disrupting this immune signaling pathway. We will next use existing and chemically designed molecules to inhibit this pathway, and examine if this prevents the processes that lead to hearing loss in cells and in zebrafish. Such molecules would be valuable starting points for developing therapies that prevent hearing loss but preserve the anti-cancer activity of cisplatin.

Background: Cisplatin is a highly effective anti-cancer drug, frequently used to treat solid tumours in children. The high frequency hearing loss that develops in over 50% of children in response to cisplatin treatment has been shown to be permanent, occur in both ears, and negatively affect speech, language and emotional development thereby, impairing the quality of life of cancer survivors. We, and others, have shown that genetic differences in patients can influence whether they develop toxicity to cisplatin treatment. Using genetic samples from Canadian children treated for cancer with cisplatin, we looked for genetic differences that are enriched in patients that do, or do not, develop cisplatin hearing loss, and identified an immunity gene that may play a role in this toxicity. We showed that cisplatin treatment induced the immunity gene in cells and that inactivating the immunity gene prevented some cellular responses to cisplatin. Many additional tools and resources have been developed to study the role of this immunity gene in the context of bacterial infections and we will take advantage of this to study its role in cisplatin hearing loss.

Current Research: The rationale of our research is that the use of the highly effective anti-cancer drug cisplatin, can be preserved if pathways that contribute to cisplatin hearing loss can be specifically inhibited. We will start by genetically deleting the key immunity gene in our candidate pathway and examine the impact on cisplatin toxicity responses in inner ear cells. Small molecules inhibitors of the immunity pathway that show potential in inner ear cells will then be examined for the prevention of cisplatin toxicity in zebrafish. Active molecules will be chemically customized to optimize their effects in both cellular and zebrafish systems, by incorporating additional chemical groups into their structure using synthetic chemistry.

Impact and Significance: Despite its anti-cancer effectiveness, cisplatin use results in hearing loss in over half of treated children, adversely impacting speech, language and psychosocial development. We currently have limited abilities to predict or prevent cisplatin hearing loss. This research will specifically address the latter, by examining if otoprotectant agents can be developed from small molecule inhibitors of pathways that cause cisplatin toxicity. Our research are a first step in the development of locally administered cisplatin otoprotectants that specifically inhibit cisplatin's side effects, while preserving its beneficial anticancer effectiveness. Such otoprotectant therapies would improve the quality of life for survivors of childhood cancer in the short and longer terms.

We gratefully acknowledge support for this work from a CIHR New Investigator Grant in Maternal, Reproductive, Child and Youth Health and by an operating grant from the Hair Massacure Program (awarded to APB); and from a University of Alberta Faculty of Medicine & Dentistry Graduate Student Recruitment Award and WCHRI graduate student award (awarded to GB).


Role of Type 3 secretion system NEL effectors in bacterial pathogenesis:

Overview: Bacteria have evolved sophisticated mechanisms to interact with other organisms, including higher order plants and mammals that they use as hosts for their own replication. It has become dogma to use mammalian and plant models to study pathogenic bacteria that have human and crop hosts, respectively, and reports that "traditional" human bacterial pathogens, such as Pseudomonas aeruginosa and Salmonella enterica, can colonize plant hosts are largely unappreciated. However, with increasing reports of S. enterica-contaminated produce, coupled with emerging literature indicating that S. enterica can use plants as hosts after subverting plant immunity, it is imperative to break with dogma and examine S. enterica pathogenesis in planta. Accordingly, the long-term vision of this research is to identify and characterize differences in the pathogenic mechanisms used by Salmonella enterica in mammalian and plant host contexts.

Background: During their interactions with plant and mammal hosts, some Gram-negative bacteria produce proteinaceous needle-like structures, termed Type 3 secretion systems (T3SS) that can directly deliver specialized protein cargo from the bacterium into the host environment. These cargo proteins are known as effectors because they induce a change in their host to benefit the bacteria. The bacterium Salmonella enterica serovar Typhimurium encodes two T3SSs positioned in Salmonella pathogenicity islands (SPI)-1 and 2, respectively. S. enterica has 3 novel E3 ubiquitin ligase (NEL) effectors, SspH1, SspH2 and SlrP, whose deletion impairs growth in infection models. NEL effectors catalyze covalent linkages of ubiquitin to host substrates, the degree of which impacts substrate function or degradation. Despite their role in infection, the fundamentals of NEL effector biology are unclear, including the mechanisms underlying their interactions with cognate host factors and their induction of altered host response.

Current Research: We aim to identify and molecularly dissect NEL binding interactions and functional outcomes in both in vitro mammalian and in planta models. Preliminary co-immunoprecipitation (IP) data indicates that SspH2 interacts with the innate immune pattern recognition receptors (PRRs). We are examining if SspH2 can activate mammalian NLRs in the absence of a cognate ligand by inducing NLR ubiquitination. We are also studying whether SspH2 immune activation antagonizes SspH1 immune suppression to reset host homeostasis.
Preliminary data indicates that SspH2 can induce immune-like phenotypes in planta in an agonist-independent manner. Accordingly, we are defining immune phenotypes elicited by SspH2 in planta by examining the induction of known genetic and biophysical markers of pattern- and effector-triggered immunity.

Impact and Significance: This work will uncover important mechanistic detail of how NEL effectors influence host responses and will shed light on whether these effectors can co-opt canonical PRRs to induce immune responses. Furthermore, this research will set the stage for identifying differences in the pathogenic mechanisms used by S. enterica in mammalian and plant hosts.
We gratefully acknowledge funding from the Li Ka Shing Institute of Virology for support for this project.

Functional pharmacogenomics of chemotherapy-related adverse drug reactions:

Selected Publications:

Association Between SLC16A5 Genetic Variation and Cisplatin-Induced Ototoxic Effects in Adult Patients With Testicular Cancer.
Drögemöller BI, Monzon JG, Bhavsar AP, Borrie AE, Brooks B, Wright GEB, Liu G, Renouf DJ, Kollmannsberger CK, Bedard PL, Aminkeng F, Amstutz U, Hildebrand CA, Gunaretnam EP, Critchley C, Chen Z, Brunham LR, Hayden MR, Ross CJD, Gelmon KA, Carleton BC.
JAMA Oncol. 2017 Nov 1;3(11):1558-1562. doi: 10.1001/jamaoncol.2017.0502.
PMID: 28448657

Pharmacogenetic variants in TPMT alter cellular responses to cisplatin in inner ear cell lines.
Bhavsar AP, Gunaretnam EP, Li Y, Hasbullah JS, Carleton BC, Ross CJ.
PLoS One. 2017 Apr 13;12(4):e0175711. doi: 10.1371/journal.pone.0175711. eCollection 2017.
PMID: 28406961

A coding variant in RARG confers susceptibility to anthracycline-induced cardiotoxicity in childhood cancer.
Aminkeng F, Bhavsar AP, Visscher H, Rassekh SR, Li Y, Lee JW, Brunham LR, Caron HN, van Dalen EC, Kremer LC, van der Pal HJ, Amstutz U, Rieder MJ, Bernstein D, Carleton BC, Hayden MR, Ross CJ; Canadian Pharmacogenomics Network for Drug Safety Consortium.
Nat Genet. 2015 Sep;47(9):1079-84. doi: 10.1038/ng.3374. Epub 2015 Aug 3.
PMID: 26237429


Role of Type 3 secretion system NEL effectors in bacterial pathogenesis:

Selected Publications:

The Salmonella type III effector SspH2 specifically exploits the NLR co-chaperone activity of SGT1 to subvert immunity.
Bhavsar AP, Brown NF, Stoepel J, Wiermer M, Martin DD, Hsu KJ, Imami K, Ross CJ, Hayden MR, Foster LJ, Li X, Hieter P, Finlay BB.
PLoS Pathog. 2013;9(7):e1003518. doi: 10.1371/journal.ppat.1003518. Epub 2013 Jul 25.
PMID: 23935490

Quantitative mass spectrometry catalogues Salmonella pathogenicity island-2 effectors and identifies their cognate host binding partners.
Auweter SD, Bhavsar AP, de Hoog CL, Li Y, Chan YA, van der Heijden J, Lowden MJ, Coombes BK, Rogers LD, Stoynov N, Foster LJ, Finlay BB.
J Biol Chem. 2011 Jul 8;286(27):24023-35. doi: 10.1074/jbc.M111.224600. Epub 2011 May 12.
PMID: 21566117

Manipulation of host-cell pathways by bacterial pathogens.
Bhavsar AP, Guttman JA, Finlay BB.
Nature. 2007 Oct 18;449(7164):827-34. Review.
PMID: 17943119

The Bhavsar lab is always interested in motivated students interested in graduate studies.
Ashley Wagner-Augustyn - Technician; NEL effectors
Ghazal Babolmorad - Graduate Student; cisplatin ototoxicity
Cole Delyea - Graduate Student
Asna Latif - Undergraduate Thesis Student; cisplatin ototoxicity
Precious Dim - Undergraduate Thesis Student; NEL effectors
Ivan K. Domingo - Summer student; NEL effectors
Adithya Shankar Subramanian - 2017 Summer Student; current graduate student in Howell lab, UofT
Johith Jacobs - 2017 Undergraduate Thesis Student; current applicant to medical school
Yani Kwok - 2017 HYRS Summer Researcher
Lindsay Stevenson - 2018 HYRS Summer Researcher
Fengting Wang - 2018 Mitacs Globalink Researcher