CAREER: Interface-induced misfolding and aggregation of intrinsically disordered proteins

University Of New Mexico, Albuquerque NM

Investigators

Abstract

Chi, Eva CBET - 1150855 Intellectual Merit NON-TECHNICAL: Despite the implication of intrinsically disordered proteins (IDPs) in a number of human diseases, the aggregation mechanism of IDP by which the disease develops remains poorly understood. The objective of this proposal is to gain a fundamental understanding of how interfaces in the cellular environment can affect the misfolding and aggregation of IDPs. The PI will investigate the aggregation of two IDPs implicated in Alzheimer¡¦s disease (AD), the amyloid-£] (A£]) peptide and the tau protein. Successful completion of the proposed research will advance current understanding of not only the interfacial effects on the structural dynamics of an important class of proteins, but also of the mechanism and thermodynamic driving forces underlying the pathogenesis of neurodegenerative diseases. TECHNICAL: The PI proposes a novel aggregation mechanism in which an IDP first forms an aggregation-competent intermediate that is partially folded and proceeds through a structurally contracted transition state. This step is followed by the assembly of intermediates to form larger aggregates. The PI hypothesizes that interfaces can induce IDP structural compaction, lowering the activation free energy of aggregation and template nucleation. The PI further hypothesizes that these interfacial effects are significantly amplified under conditions that mimic the cell milieu, namely, macromolecular crowding and the presence of osmolytes. The PI hypothesizes that attenuating the binding of A£]'n peptide and tau protein to biological interfaces can inhibit their aggregation and toxicity. To test these hypotheses, the PI proposes the following three objectives that build on her research group¡¦s unique strengths in thermodynamics of protein aggregation, biophysical analysis of proteins in solution and at interfaces, and biochemistry. The PI proposes to accomplish the following three research objectives: 1) to evaluate the likelihood and affinity of four tau proteins to partition to two interfaces, the air/water interface and the lipid membrane interface, and characterize changes in tau structure and aggregation kinetics accompanying the binding of the proteins to the interfaces; 2) to study the effect of molecular crowding and osmolytes on A£]'nand tau¡¦s surface activity, membrane interaction, and aggregation to test if interfacial forces stemming from excluded volume and preferential exclusion can modulate interface-templated IDP aggregation; 3) to investigate whether attenuation of the binding of A£]'nand tau to lipid membranes can ameliorate their aggregation and toxicity. Broader Impacts The proposed research, deeply rooted in molecular thermodynamics and interface science, represents a novel approach to studying the aggregation of IDPs. The analysis of intermolecular interactions and interfacial forces that govern the assembly of IDPs represents a fundamental scientific challenge that is of great importance in biology and medicine. Understanding of the mechanism and thermodynamic driving forces of IDP aggregation gained from the proposed study is of paramount importance in advancing the current knowledge of the molecular mechanism underlying the pathogenesis of Alzheimer¡¦s disease. Determining the aggregation mechanism of IDPs could potentially lead to therapeutic strategies for treating such neurodegenerative diseases. In terms of education, the PI is committed to furthering her contribution to the establishment of New Mexico¡¦s first Biomedical Engineering undergraduate and graduate degree programs through new course development and student recruitment. The PI is also strongly dedicated to expanding and augmenting the existing outreach efforts at the University of New Mexico to rural Native American elementary schools and introducing a new hands-on demonstration module focusing on the molecular aspects of protein structure and denaturation to Albuquerque High School students. The PI will continue mentoring efforts to Native American students from the Southwest Indian Polytechnic Institute helping them make a successful transition to the University of New Mexico. The cumulative and long-term impact of the proposed educational and outreach efforts will be increased enrollment and retention of students in bioengineering, particularly underrepresented minorities and women, which will spark economic vitality and meet future work force demands in New Mexico and beyond.