Chemistry Colloquium: Dr. Galia Debelouchina

The Department of Chemistry in the College of Arts and Sciences is pleased to welcome Dr. Galia Debelouchina, an associate professor at the University of California San Diego.

Title: Capturing the Interactions of Small Heat Shock Proteins and Their Clients with Advanced NMR Spectroscopic Tools

Abstract

Cells regulate condensate formation and aberrant protein aggregation through the action of chaperones, including the ATP-independent small heat shock protein HSPB1/Hsp27. The HSPB1 monomer consists of a central α-crystallin domain (ACD) flanked by an N-terminal domain (NTD) and a C-terminal domain (CTD). In the absence of client proteins, HSPB1 assembles into polydisperse oligomers that have presented a significant challenge for structural characterization due to their heterogenous and dynamic nature. While the interactions of several client proteins and HSPB1 dimers stabilized by mutations have been described by solution NMR spectroscopy, how the wild-type HSPB1 oligomers regulate proteins in the context of biological condensates and protein aggregation is still unknown. Here, we use magic angle spinning (MAS) NMR spectroscopy to capture the structure and dynamics of HSPB1 oligomers in the presence and absence of the low complexity domain (LC) of the fused in sarcoma (FUS) protein. Our work has significantly benefited from recent advances in the field that have allowed us to record high resolution ¹H-based correlations of just 50 μg of fully protonated 250 – 500 kDa HSPB1 oligomers. We have combined this methodology with intein-mediated segmental labeling and coarse-grained molecular dynamics simulations to paint a comprehensive picture of the interactions of each HSPB1 domain in the context of oligomers and in the presence of FUS LC. Our results point to the importance of the NTD domain in mediating interactions with aggregating client proteins and condensate regulation.