To live or Die: Dissecting the role of Liquid- Liquid Phase Separation in Membrane Protein Triage.

Correct protein localisation is vital for cell function and health. However, the sorting process is not always efficient, with failure rates of 5-10% for endoplasmic reticulum (ER)-bound proteins, rising to over 40% for some precursors. Cells employ energy-intensive mechanisms to identify and target mislocalised proteins for degradation. However, these defences can be overwhelmed due to mutations, stress, or aging; leading to misfolding and aggregation, linked to cancer and neurodegenerative diseases. The SGTA/BAG6 complex plays a pivotal role in degradation of mislocalised membrane proteins and targeting tail-anchored membrane proteins to the ER. However, the mechanisms of discrimination between seemingly similar proteins remains unclear. Our project aims to uncover how this machinery distinguishes "healthy" tail-anchored membrane proteins en-route to the ER from "faulty" mislocalised proteins destined for degradation. In our pilot studies, we have identified liquid-liquid phase separation (LLPS) as a potential discriminating mechanism. Using a multidisciplinary approach, we will investigate the role of LLPS in membrane protein triage within the SGTA/BAG6 complex. Objectives: 1.    Investigate how LLPS influences membrane protein triage. 2.    Identify key proteins that govern the discrimination process via LLPS. 3.    Determine how LLPS impacts fate and dynamics of membrane proteins. 4. Develop high-throughput microfluidics to study LLPS