RUFY1: A sorting station of endolysosomal system

Work done in the lab of Prof. Mahak Sharma at IISER Mohali

About author

Shalini Rawat is a graduate student at the Indian Institute of Science Education and Research (IISER) in Mohali, working in Dr. Mahak Sharma’s lab. Shalini obtained a B.Sc. (H) in Microbiology from the Institute of Home Economics at Delhi University before pursuing a master’s degree in Biotechnology at the Indian Institute of Technology (IIT) in Bombay. At IIT Bombay, she worked on her master’s thesis with Dr. Anirban Banerjee in the Microbial Pathogenesis Lab. Shalini is interested in studying the mechanisms regulating cargo trafficking to the lysosome, as well as the distribution and biogenesis of the lysosomal compartments. She is currently working on her thesis and looking for postdoctoral positions in cell biology labs. Shalini enjoys watching movies, listening to music, and occasionally cooking in her spare time.

Interview

How would you explain your research outcomes to the non-scientific community?

Imagine a human cell as a big factory with various departments/units, each responsible for a different function such as manufacturing, packaging, and transportation of the final product to customers. Human cells are similarly organized internally into smaller compartments for specific functions such as the endoplasmic reticulum (ER) for protein synthesis, the mitochondria for energy production, and the golgi for protein processing and transport to their final location. To conserve resources and manage waste generated by the manufacturing unit, factories also have a recycling unit for the reuse and recycling of waste and unnecessary materials. Although we have only recently learned to recycle materials from our daily lives, our cells have evolved a specialized compartment known as a “lysosome” billions of years ago that is responsible for breaking down old, unwanted, and damaged materials into smaller molecules for reuse by cells. Lysosomes contain digestive enzymes that act as molecular scissors to chop off the unwanted waste. These enzymes are required for lysosome function and are processed in the Golgi, where they are loaded into transporter proteins (receptors) and delivered to the lysosome. Following delivery in the lysosome, these transporters must return to the golgi for another round of transport. Our findings demonstrate the role of the protein RUFY1, in mediating the movement of transporter proteins to the golgi to carry out the delivery of enzymes to lysosomes (see Fig. 1).

Understanding how the movement of any cellular material from one compartment to another is regulated has significant physiological implications. Lysosome dysfunction has been linked to a variety of human diseases, including lysosomal storage disorders (LSDs), metabolic disorders, cancer, and neurodegenerative diseases such as Parkinson’s, Alzheimer’s, frontotemporal dementia (FTD), and amyotrophic lateral sclerosis (ALS). One of the major underlying causes of most of these disorders is improper transport of lysosomal enzymes, which makes the lysosome less degradative. As a result of the accumulation of cellular waste, lysosomes become swollen and enlarged, a characteristic phenotype of lysosomal dysfunction. In summary, our findings contribute to a better understanding of how lysosome function is regulated.

How do these findings contribute to your research area?

Previous studies from our lab and other groups have shown that the GTP-binding protein Arl8b brings several interaction partners to the lysosomal compartment to mediate lysosome movement and regulate the transport of cellular cargo to the lysosome for degradation. Our recent work sheds light on the new role played by Arl8b, which was previously known to localize and function predominantly on late endosomal and lysosomal compartments. We show that Arl8b interacts with RUFY1 on early/sorting endosomes, asserting that Arl8b has another subcellular location and raising interesting questions about Arl8b and its role in the regulation of lysosome functions. Our findings also provide detailed mechanistic insights into how RUFY1 interacts with the molecular motor “dynein” on the sorting endosome to mediate the movement of receptor proteins for lysosomal enzymes to the golgi.

“Our work sheds light on the new role played by Arl8b, which was previously known to localize and function predominantly on late endosomal and lysosomal compartments.”

What was the exciting moment during your research?

Though I had many exciting moments during this work, most of which were associated with immunofluorescence data, I was overjoyed to see the high-resolution images of RUFY1 by structured illumination microscopy (SIM), which resembled a donut. I was also astounded to see the dynamics of sorting nexin 1 (SNX1) positive tubules emanating from RUFY1 donuts in a SIM live-imaging experiment (see Fig. 2).

What do you hope to do next?

I am currently looking for post-doctoral opportunities in cell biology labs to pursue my career in research. In future, I would like to explore the lysosome connections and communication mechanisms with other organelles such as endoplasmic reticulum and mitochondria. I think it is exciting to understand how organelles talk to each other.

Where do you seek scientific inspiration from?

My inspiration comes from many different sources. I believe that we can find inspiration in our surroundings, including our peers, mentors, and even students. I am grateful to all of my teachers throughout my high school and undergraduate years for helping me recognize and pursue my interest in science. Dr. Mahak Sharma, an incredible scientist and person, inspired me throughout my Ph.D. and taught me a lot. Mahak inspired me to think logically, to use my own imagination, and to come up with new ideas. She strongly encouraged me to present my work at conferences and workshops, as well as interact with other scientists. Aside from that, the team (all MS Lab members) is what motivates you to come to the lab and get right to work. I had the privilege of working with and training incredible IISER students (BS-MS and Integrated PhD program) who encouraged me to learn from my mistakes and actively participate in scientific discussions. Finally, my mother is my inspiration and role model for perseverance, patience, and, most importantly, never giving up.

How do you intend to help Indian science improve?

In my opinion, India is doing well in science, but in order to improve research quality even further, we need to promote collaborative research from interdisciplinary fields not only within India but around the world, which will allow for the exchange of ideas and technical skills. If given the opportunity, I would also like to volunteer for public outreach programs that communicate with high school and undergraduate students about research opportunities and foster scientific curiosity.

Apart from these, I will be very much willing to actively engage in promoting scientific collaboration between industries and academia, which, in my opinion, will improve Indian science by presenting a broader career prospect to young scientists and by ensuring larger funding opportunities. I believe a collective and persistent endeavor in this direction will make a positive change in our science.

Reference

Shalini Rawat, Dhruba Chatterjee, Rituraj Marwaha, Gitanjali Charak, Gaurav Kumar, Shrestha Shaw, Divya Khatter, Sheetal Sharma, Cecilia de Heus, Nalan Liv, Judith Klumperman, Amit Tuli, Mahak Sharma; RUFY1 binds Arl8b and mediates endosome-to-TGN CI-M6PR retrieval for cargo sorting to lysosomes. J Cell Biol 2 January 2023; 222 (1): e202108001. doi: https://doi.org/10.1083/jcb.202108001

Copy Editor

Ritvi Shah

Postgraduate at Vikram Sarabhai Institute

Postgraduate at Vikram Sarabhai Institute of Cell and Molecular Biology, Gujarat. She is a neuroscience enthusiast. Apart from that, she enjoys reading and trying her hand at sciart.

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