ABSTRACT
First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping researchers promote themselves alongside their papers. Caroline König is first author on ‘ Vps41 functions as a molecular ruler for HOPS tethering complex-mediated membrane fusion’, published in JCS. Caroline is a postdoc in the lab of Christian Ungermann at Osnabrück University, Osnabrück, Germany, working on understanding endosomal tethers in yeast using a combination of structural analysis and in vitro experiments.
Caroline König
How would you explain the main findings of your paper in lay terms?
This study centers on the conserved HOPS tethering complex. In cells, this hexameric protein complex localizes on the surface of the lysosome (or the vacuole in yeast), which is the ‘cellular stomach’. From there, it orchestrates the membrane fusion of incoming vesicles carrying ingested material. For membrane tethering, HOPS binds GTP-loaded Ypt7 via its subunits Vps41 and Vps39, and for subsequent fusion, it assembles SNAREs from opposing membranes. Building on previous work from our lab that resolved the structure of the HOPS tethering complex, we investigate the mechanisms underlying HOPS-dependent tethering and fusion processes. Structural analysis of one HOPS subunit, Vps41, shows clear indication of flexibility in one-half of the protein. We mutate this region of Vps41 and investigate whether this impairs complex functionality. We find that when we shorten the protein, the complex still binds to membranes but fails to promote membrane fusion. However, when we replace the truncated region with a random amino acid sequence, we can rescue the fusion phenotype. Our results suggest that the correct length, rather than the amino acid sequence, of the truncated region is necessary for HOPS to fulfil its function. Our findings provide a better understanding of the role of this protein in membrane fusion.
Were there any specific challenges associated with this project? If so, how did you overcome them?
The initial cloning step for the different mutants was a challenge. Given that we were comparing several mutations in parallel, each leading to different in vivo and in vitro phenotypes, it was quite chaotic at the start and throughout the project. The complexity increased further when we additionally built the constructs for the overexpression strains. However, with the help of our wonderful technician, Kathrin Auffarth, who never lost track of the correct clones and strains amid the ‘genetic chaos’, we managed to overcome this challenge.
When doing the research, did you have a particular result or ‘eureka’ moment that has stuck with you?
When I was close to finishing my PhD, I was doing the final experiments for this paper. In the very last week of working in the lab, I was finally able to test the phenotype of the Vps41 linker rescue mutant, as it had taken a while to build the strain. To my surprise, the vacuoles looked like those of the wild type, leaving me speechless for a moment. At that time, I did not know I would return to the lab as a postdoc, so I had mixed feelings, with many open questions in my head. However, I am now more than happy that this cool result has been published!
Why did you choose Journal of Cell Science for your paper?
We aimed to publish in Journal of Cell Science because the journal's high standards for review and publication align with our expectations and requirements. In addition, its focus on cell biology is a great match for our work.
Have you had any significant mentors who have helped you beyond supervision in the lab? How was their guidance special?
In addition to the great support I received in the lab, which I continue to benefit from, there are a few people who have been fundamental to my research over the past few years. In particular, my former colleague and friend Dr Ann-Christin Borchers, now a postdoc in Oslo, Norway, has helped me countless times to overcome personal fears and believe in myself. Additionally, my friends outside of my science bubble have always been there for me, offering support through difficult times.
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?
Becoming an expert in this field is what inspires and motivates me. The longer I stayed in science, the more I felt I was mastering my own research. During my PhD, I had the opportunity to present my work at a conference. The realization that I was making an important contribution and receiving recognition in the field motivated me to keep going.
Who are your role models in science? Why?
Personally, I cannot name a specific role model in science who has had a direct impact on my research and me. However, I am thrilled by the dedication with which scientists engage with a specific topic. For me, scientists who are passionate about their work are a daily inspiration. I feel privileged to witness this kind of dedication every day in my work environment.
What's next for you?
I would like to stay in academia for another year or two before moving on. Last year, while writing my thesis, I realized how much I miss working in the lab. So, I am really happy to be back for a postdoc period. What comes next? I don't know, but I believe there are great opportunities out there. For now, I am focused on enjoying my work here.
Tell us something interesting about yourself that wouldn't be on your CV
I love to spend my weekends in a café where I have coffee, a piece of cake and good conversations with my partner, friends or family. These are the moments where I can relax and calm down after a long week. I am always in to check out new places to go.
Caroline König’s contact details: Osnabrück University - Department of Biology/Chemistry, Biochemistry section, Barbarastraße 13, 49076 Osnabrück, Germany.
E-mail: [email protected]
