Hui Sun

Professor, Physiology, University of California Los Angeles

Professor, Ophthalmology, University of California Los Angeles


Laboratory Address:
CHS 53-140

Work Address:
CHS 53-140A

Office Phone Number:

Dr. Sun's lab has focused on the discovery, mechanistic study and identifying small molecule modulators of novel membrane receptors that play important roles in physiology and diseases. To achieve these goals, several new techniques have been developed by his lab. The first major discovery is the membrane receptor that mediates cellular uptake of vitamin A, a chemical essential for human survival. This receptor is expressed in blood-organ barriers and eluded identification for more than 30 years. Another discovery is the signaling receptor for the most potent endogenous inhibitor of angiogenesis. This receptor is highly specifically expressed in pathogenic blood vessels including tumor blood vessels. By developing a novel fluorescence-based technique, his team and collaborators identified potent chemical compounds that target this receptor to specifically kill tumor blood vessels to lead to effective tumor killing in vivo. In the past few years, his lab also developed a novel technique to screen for receptor-activating antibodies and successfully identified antibody drug candidates of this receptor after large-scale screening 10 billion human antibody clones in collaboration with scientists within and outside of UCLA.


Member, Biochemistry, Biophysics & Structural Biology GPB Home AreaBrain Research InstituteMolecular, Cellular & Integrative Physiology GPB Home Area

Research Interests

Receptors are among the most successful therapeutic targets in medicine. We are interested in the discovery and mechanistic study of new membrane receptors that play critical roles in physiology and diseases and to target these receptors to develop novel small molecule-based therapeutics. In 2007, we solved a three decades-old scientific problem by identifying a new type of receptor using a new technical strategy. This multitransmembrane receptor mediates cellular uptake of vitamin A, a chemical compound that has diverse biological functions in different organs and is essential for human vision and human survival. Using sensitive real-time monitoring techniques that we developed, we revealed that the transmembrane transport mechanism of this receptor/transporter is unlike any known receptor or transporter and further identified small molecules the potently modulate its activity. Another long-standing scientific problem that we tackled was to identify the transmembrane receptor for the most potent endogenous antiangiogenic factor that is known to suppress the pathogenesis of several major diseases. This was previously an insurmountable hurdle that prevented the development of small molecule-based medicines directed at this natural therapeutic pathway. We recently identified the receptors for this factor as a new type of transmembrane receptors with a new signaling mechanism. We further developed an innovative cell-based technique to identify chemical compounds that specifically target these receptors, and we identified the first chemical compounds that mimic the factor’s function in vitro and in vivo. These novel chemical compounds are potential first-in-class drugs to treat devastating blinding diseases and cancer.


Dr. Sun is Professor of Physiology and Ophthalmology in the Department of Physiology and Stein Eye Institute, David Geffen School of Medicine at UCLA. He is also a member of the Jonsson Comprehensive Cancer Center. He received his Ph.D. from Johns Hopkins University in 1998. He came to UCLA in 2003 as an Assistant Professor and received the prestigious Early Career Scientist Award from the Howard Hughes Medical Institute in 2009. He has taught in a variety of courses related to physiology and human diseases at UCLA Medical School, UCLA Dental School and UCLA Graduate School.


A selected list of publications:
  • Kawaguchi, R., Yu, J., Honda, J., Hu, J., Whitelegge, J., Ping, P., Wiita, P., Bok, D., and Sun, H.   A membrane receptor for retinol binding protein mediates cellular uptake of vitamin A, Science, 2007; 315: 820-825.
  • Yang, Z., Camp, N., Sun, H., Tong, Z., Gibbs, D., Cameron, J., Chen, H., Zhao, Y., Pearson, E., Li, X., Chien, J., DeWan, A., Harmon, J., Bernstein, P., Shridhar, V., Zabriskie, N., Hoh, J., Howes, K., and Zhang, K.   A variant of the HTRA1 gene increases susceptibility to age-related macular degeneration, Science, 2006; 314: 992-993.
  • Jin, M., Li, S., Moghrabi, W.N., Sun, H., and Travis, G.H.   RPE65 is the retinoid isomerase in bovine retinal pigment epithelium, Cell, 2005; 122: 449-459.
  • Sun, H., and Kawaguchi, R.   The Membrane Receptor for Plasma Retinol Binding Protein, a New Type of Cell-Surface Receptor, Int Rev Cell Mol Biol. , 2011; 288(1-41): .
  • Kawaguchi, R., Yu, J., Ter-Stepanian, M., Zhong, M., Guo, C., Yuan, Q., Jin, M., Travis, G.H., Ong, D., and Sun, H.   Receptor-Mediated Cellular Uptake Mechanism that is Coupled to Intracellular Storage, ACS Chemical Biology , 2011; 6: 1041-51.
  • Cheng, G., Zhong, M., Kawaguchi, R., Kassai, M., Al-Ubaidi, M., Deng, J., Ter-Stepanian, M., and Sun, H.   Identification of PLXDC1 and PLXDC2 as the Transmembrane Receptors for the Multifunctional Factor PEDF. , eLIFE, 2014; 3: e05401.
  • Zhong, M., and Sun, H.   A Genetic Clog in the Vitamin A Transport Machinery, Cell, 2015; 161 (3): 435-437.

Awards and Honors

  • E. Matilda Ziegler Foundation Award, E. Matilda Ziegler Foundation, 2005-2008.
  • Alicia Showalter Reynolds Research Prize, Johns Hopkins University, 1998.
  • Ellison Medical Foundation New Scholar Award, Ellison Medical Foundation, 2006-2010.
  • Gerald Oppenheimer Family Foundation Award, UCLA, 2005.
  • Howard Hughes Medical Institute Early Career Scientist Award, Howard Hughes Medical Institute, 2009-2015.
  • Karl Kirchgessner Foundation Award, Karl Kirchgessner Foundation, 2003.
  • Ruth and Milton Steinbach Award, Ruth and Milton Steinbach Foundation, 2004-2007.
  • Stein-Oppenheimer Endowment Award, UCLA, 2004.