ABSTRACT
First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Susan Lassen is first author on ‘Perilipin-2 is critical for efficient lipoprotein and hepatitis C virus particle production’, published in Journal of Cell Science. Susan is a post-doc in the lab of Eva Herker at the Heinrich Pette Institute, where she uses basic science approaches to understand the interplay of lipid droplets with the hepatitis C virus.
Susan Lassen
How would you explain the main findings of your paper in lay terms?
The cell needs energy for living and uses so-called lipid droplets (LDs), which are balls, of fat to provide energy when the cell is in demand. These fat balls can come in different ‘flavors’ as they have different combinations of proteins attached depending on the cell type. In the liver, the main protein is PLIN2. The hepatitis C virus (HCV) mainly attacks the liver and uses these LDs to make more virus. So far, little is known how PLIN2, LDs and HCV influence each other. Therefore, we changed the protein combinations of the fat balls by removing PLIN2 from the LDs and analysed if and how this alters the shape of the LDs and how it influences the life cycle of the virus. We found that in cells without PLIN2, the fat balls were slightly larger and were trapped in a sack of membranes, which hindered the accessibility of the virus to LDs and led to loss of fitness of the virus.
Were there any specific challenges associated with this project? If so, how did you overcome them?
The knockdown of PLIN2 resulted in a strong reduction of HCV viral particle production. The main challenge was to figure out why depletion of PLIN2 resulted in impaired virion morphogenesis. We used a broad spectrum of different methods to decipher the interplay between PLIN2, LDs and HCV infection. For example, we analyzed the production of apolipoprotein E, a known host factor for HCV that is important for the lipidation of infectious low-density of viral particles. In PLIN2-depleted cells, we found reduced protein levels and secretion of ApoE, and that the HCV viral particles were of higher density. We were able to restore ApoE levels in PLIN2-knockdown cells by overexpressing ApoE but unfortunately not HCV viral production. However, we also observed a strong trafficking defect of the viral proteins NS5A and core protein to LDs. By using electron microscopy, we discovered major membrane alterations surrounding LDs. Thus, PLIN2 expression is required for the proper LD architecture that is needed for trafficking of viral proteins to LDs and for formation of functional low-density HCV particles prior to ApoE incorporation.
…we found major membrane alterations in cells lacking PLIN2. This was one of our major findings.
When doing the research, did you have a particular result or ‘eureka’ moment that has stuck with you?
We performed confocal microscopy to see if the LD morphology changes. It certainly does, but without changes in total LD content. We then decided to perform electron microscopy and indeed, we found major membrane alterations in cells lacking PLIN2. This was one of our major findings.
Why did you choose Journal of Cell Science for your paper?
We chose Journal of Cell Science to reach a broad spectrum of scientists. Additionally, this journal has a strong focus on different microscopy techniques, and our paper covers several microscope methods and therefore we thought this paper fits well in this journal.
What motivated you to pursue a career in science, and what have been the most interesting moments on the path that led you to where you are now?
After completing my diploma studies, I worked for some years in industry. As I was scientifically somewhat limited in my daily work, I decided to pursue my career in academia where I was able to work independently and could focus on topics I am interested in. At this point, I would like to thank my supervisor and group leader Eva Herker. She gave me the opportunity to work that way, but she was also always helpful and open minded in her discussions about the project. I very much enjoyed working in her lab.
What's next for you?
The paper was part of my PhD. I will be starting a new position as a post doc in a different lab focusing on the development of vaccine strategies and on the immunity to viral infections.
Tell us something interesting about yourself that wouldn't be on your CV
All my friends and colleagues would say I am crazy about good coffee. As a present, I got an espresso hand pump with which I can brew my own coffee wherever I am, for instance, on conferences where good coffee is rare.
Electron microscopy of HCV-infected shPLIN2-transduced cells. *, LD; colored arrowheads: red, double membrane sac; white, LD membrane contacts; cyan, single-membrane vesicles; yellow, double-membrane vesicles; Nu, nucleus.
Susan Lassen's contact details: Heinrich Pette Institute, Hamburg, Germany.
E-mail: [email protected]
