Document Type
Conference Proceeding
Publication Date
5-1-2026
Journal / Book Title
Journal of Biological Chemistry
Abstract
Phase separation is a process of molecular segregation in space. Increasing evidence suggests that spatial organization of biochemical molecules in cells is governed by the principle of phase separation. Multivalent binder proteins tend to form fluidic protein condensate and plasma membrane lipid composition tend to form lipid raft domain. On plasma membranes, the two types of phase separation is known to collaboratively segregate membrane cargo molecules leading to phase separation clustering. More evidence is being found that poly Ubiquitin (polyUB) proteins under certain circumstances have potency to phase separate into condensates. polyUB tagging of membrane proteins is often a first step leading to the downstremp vesicle trafficking process such as lysosomal degradation, thus phase separation clustering may play a role in efficient cargo sorting and catalyzing the recruitment of downstream trafficking proteins. However, the role of polyUB cargo molecules in clustering has been underexplored. We used epi fluorescence microscopy and synthetic giant unilamellar vesicles to study polyUB cargo clustering on the membranes. E.Coli protein expression and synthetic crosslinking of short peptides were used to come up with model proteins to quantitatively study their clustering behavior on the membranes. polyUB cargo on ternary mixture membranes of saturated chain lipids, unsaturated chain lipids, and cholesterol collaboratively clustered when interacted with multivalent UB binding proteins. Multi-valency, structure, cargo density, and membrane composition affected the final outcome. Our current model is that lipid raft segregation and protein condensate formation collaboratively promote phase separation clustering of polyUB cargo and the degree of interaction may be affected or even reversed by the nature of lipid environment, how the proteins are anchored to the membranes, and protein density. This implies that polyUB cargos interacting with multivalent downstream trafficking proteins may play an important roles in physiological cargo sorting process to initiate the vesicle trafficking.
DOI
10.1016/j.jbc.2026.112248
Montclair State University Digital Commons Citation
Lee, Il-Hyung, "Phase separation clustering of poly Ubiquitylated cargos in plasma membrane vesicle trafficking" (2026). Department of Chemistry and Biochemistry Faculty Scholarship and Creative Works. 662.
https://digitalcommons.montclair.edu/chem-biochem-facpubs/662
Published Citation
Lee, I. H. (2026). Phase separation clustering of poly Ubiquitylated cargos in plasma membrane vesicle trafficking. Journal of Biological Chemistry, 302(5).