Mapping Binding Domains between HAX1, HSP90, and PLN

• Julia Serjantova, Applied Molecular Biology & Biotechnology, University of Delaware

• Chi Keung Lam, Biological Sciences, University of Delaware

Heat Shock Protein 90 (HSP90) is a chaperone protein relevant in a number of pathways in the body, by being involved in the quality control of its client protein folding status. HSP90 has been shown to be involved in calcium kinetics in the cardiomyocytes through its ability to modulate the HAX1/PLN/SERCA2a regulatory complex which plays a key role in cardiac contractility. Previous work done by Dr. Lam has shown that overexpression of HAX1 pulls HSP90 away from the IRE1 pathway and instead towards the PLN/SERCA2a complex. Interestingly, IRE1, an HSP90 client protein, has been shown in prior studies to be linked to increased cardiac stress and cell apoptosis in IR injury models. Because impaired contractility and increased cell death are hallmarks of most cardiac diseases, directing studies towards PLN/SERCA2a presents a feasible approach in addressing cardiac disease therapeutically by targeting molecular and cellular pathways, particularly the calcium signaling pathway. The research presented here is focused on studying the specificity of these interactions between the HAX1 protein and HSP90 by expressing fragments of these proteins through the use of expression vectors and bacterial cultures and using binding assays to determine what fragments of these proteins are interacting and how. From this study, we were able to confirm that HAX1 and HSP90 interact with each other through the use of protein binding assays and western blots. Next steps would be to verify interactions between PLN and HSP90 and ultimately study the specificity of these interactions by expressing fragments of these proteins and performing binding assays.