Illustration of a neural network

Hong Kong researchers gain new insights into cell biology

28 May 2024

Living cells contain numerous membraneless organelles. Unlike traditional organelles that are enclosed by lipid bilayers, membraneless organelles form through liquid-liquid phase separation, creating distinct compartments within the cell without the need for a surrounding membrane.

These organelles must be separated as distinct cellular subcompartments to carry out specific cellular functions. Despite this, the precise molecular mechanisms responsible for maintaining this segregation are not well understood.

Within neuronal synapses, the postsynaptic cytomatrices of excitatory (ePSDs) and inhibitory (iPSDs) synapses are examples of membraneless organelles that remain segregated even within small spine protrusions.

A research team led by Professor Mingjie Zhang at the Hong Kong University of Science and Technology has now shown that ePSD and iPSD condensates each form a percolated network through specific molecular interactions and are naturally segregated from each other. Forced interaction between ePSD and iPSD proteins with a nanomolar binding affinity cannot mix ePSD and iPSD condensates together, indicating that demixing is a default process for biomolecules in membraneless organelles formed by phase separation.

Their findings, recently published in Science, shed important light on the fundamental mechanisms that govern the organisation of cellular structures.

Professor Mingjie Zhang is the recipient of two Croucher Senior Research Fellowships (2003 and 2018).