Inflammation is the body’s response to clear out pathogens upon infection or initiate tissue repair upon injury. It is a strictly regulated process that follows three general stages: initiation, execution and resolution. While essential to homeostasis, inflammation must be strictly regulated to avoid excessive tissue damage. My work focuses on a fairly recently appreciated family of molecules involved in resolution of inflammation. Siglecs (sialic acid binding immunoglobulin-like LECtins) are cell surface proteins, members of the immunoglobulin-like gene superfamily that bind sialic acid-containing glycans (sialoglycans). Selective expression of Siglecs on subsets of inflammatory cells and their potential to mediate inhibitory signaling through their ITIM motifs makes them appealing therapeutic targets to suppress ongoing inflammation and limit inflammatory tissue damage. Among the inhibitory siglecs is Siglec-8. Siglec-8 is selectively expressed on allergic inflammatory cells (eosinophils and mast cells) in the periphery and microglia in the brain. Crosslinking Siglec-8 by antibody or glycan ligands induces eosinophil apoptosis, inhibits release of inflammatory mediators by mast cells, and is proposed to inhibit microglial phagocytosis. Productive Siglec signaling requires the Siglec and its sialoglycan target (ligand) in tissues. My research spearheaded the discovery of endogenous Siglec-8 sialoglycan ligands on human airways and brain. Since Siglec-8 is uniquely human, I purified Siglec-8 ligands from human trachea, nasal lavage from patients with inflamed and non-inflamed airways, and brain cortex from non-demented and Alzheimer’s disease donors. I discovered that Siglec-8 ligands in all tissues are sialylated keratan sulfates with a characteristic glycan structure having a sialic acid adjacent to a sulfated galactose. This structure is appended to different proteins depending on the tissue. In each case, Siglec-8 ligand expression is upregulated under inflammatory conditions, suggesting tissue-level regulation of ongoing inflammation. Further studies will determine the role of regulated Siglec sialoglycan ligand expression in mediating microglial activity in dementia and allergic inflammatory cells in eosinophilic diseases. This work was done in the lab of Ronald L. Schnaar, Ph.D., in the Department of Pharmacology and Molecular Sciences, where we seek to further understand the role of glycans and glycan-binding proteins in diseases affecting humans.
Questions & Answers
Why did you choose Johns Hopkins for your work?
I chose Johns Hopkins University not only because it is among the top research universities worldwide, but also because I was lured by the collaborative environment and welcoming culture in the Department of Pharmacology and Molecular Sciences. Also, the school of medicine has a diverse group of labs studying the role of glycans and glycan-binding proteins in disease and disease progression.
What does receiving this award mean to you personally and professionally? Do you have any connection with the particular award you received?
Personally, I feel honored to receive this award, especially because I know that my research was chosen out of an “exceptionally large number of excellent applications.” Professionally, I love the opportunity to bring awareness to the importance of glycans and glycan-binding proteins in almost every aspect of biology. In addition, receiving the A. McGehee Harvey Award makes this award even more meaningful to me because Dr. Harvey was an excellent biomedical scientist who focused on human diseases and believed patients themselves were the best teachers of biomedical knowledge. My research focuses on studying human diseases using human tissue because the glycan-binding protein I study has rapidly evolved, and there is no defined ortholog in mouse.
What contributed to your project's success?
Above all, I am grateful for the opportunity I was given to direct and manage my current projects. My project’s success is dependent on many factors. First of all, my grit and desire to fulfill the goals set out for the project have definitely driven its success. As with any research project, there have been many challenges to overcome, but I have persevered. Second, my mentors Ronald L. Schnaar and Jean Kim, have provided their guidance, expertise and time to help me push this project forward. Third, it would have been nearly impossible to cover so much ground and advance the project this far without the help of many collaborators. Kazuhiro Aoki and Michael Tiemeyer from Complex Carbohydrate Research Center in Athens, Georgia, as well as Zaikuan J. Yu and Benjamin Orsburn in Namandjé Bumpus’ lab here at Hopkins in the Department of Pharmacology, who analyzed samples by mass spectrometry. Bruce Bochner at Northwestern University and his lab members performed eosinophil apoptosis assay. James Paulson and Corwin Nycholat at Scripps Research Institute in La Jolla provided synthetic glycans for competition assays. Steve Fernandes optimized many of the protocols used in the Schnaar lab, which I have used for my project. Schnaar lab members have also provided support and feedback essential to the project’s progress. In summary, my project’s success is the result of invaluable collaborations that have been key to obtain data that would otherwise be hard or impossible to obtain on my own.
What thoughts do you have about Young Investigators’ Day itself, as a celebration of the roles students and fellows play in research at Johns Hopkins?
I think it is great to highlight the work of students and fellows at Hopkins. Principal investigators get a lot of opportunities to share their research, but students and fellows do not. Young Investigators’ Day is a great way to give that opportunity to students and fellows.
What has been your best/most memorable experience while at Johns Hopkins?
I have enjoyed being able to talk to other Hopkins scientists and trainees whenever I have come across experimental setbacks. It is very comforting knowing that if something goes wrong, an experiment does not work, I can always ask others for their help. For example, when I was having a hard time preparing samples for mass spectrometry analysis, Zaikuan and Benjamin helped me refine the protocol to get purified sample ready for analysis.
What are your plans over the next year or so?
I am planning to apply for grants this year, and looking for a faculty position in the near future.
Tell us something interesting about yourself.
I was born in Cuba and emigrated to the U.S. as a teen. Soon thereafter, my interest in science blossomed when I helped my aunt learn chemistry. I consider myself very modest and shy, answering these questions and talking about myself is quite scary to me. However, I would like to take the opportunity to inspire someone else. We should not let fear stop us from pursuing our goals and dreams. If we persevere, we can and will overcome anything that life throws at us.