CAREER: The molecular interplay between integrin adhesion, allostery and shape-shifting

Adhesion molecules are proteins on cell surfaces that facilitate cellular adhesion, migration, and interactions with the external environment. These adhesion molecules, specifically called integrins, share an almost identical topology and are highly proficient, precise, and specific at ambient conditions. Moreover, they are highly evolvable and easily adapt to new mechanisms. Integrin α/β heterodimers are expressed in all animals (from sponges to vertebrates), bind different ligands, and at least one integrin is expressed in each human cell type. Exactly how each integrin has been diverged to play a particular role is largely unknown due to the lack of quantitative studies characterizing their structural changes and adhesion properties on cell surfaces. This research will focus on defining the structural and adhesive properties of a white blood cell-specific integrin receptor, which is only present in vertebrate animals. This research will employ biophysics, biochemistry, structural biology, and chemistry approaches to relate the changes in this leukocyte integrin’s conformation and adhesion. The biotechnology summer workshop, designed for K–12 STEM students and undergraduates who are training to be future STEM teachers, will provide insight into the fundamental understanding of biomolecular structures and how alterations in these structures are related to protein function. Leukocyte integrins allosterically communicate mechanical and biochemical information and regulate many cellular events that involve leukocyte migration, diapedesis towards the site of tissue damage or infection, and phagocytosis. How do leukocyte integrins achieve such diverse functions while allosterically regulating their affinities and structures? The overarching objective of this proposal is to quantify its conformational kinetics that are thermodynamically equilibrated between different integrin conformations, measure the occupancy and intrinsic affinities, and determine cryo-EM structures of each leukocyte integrin conformational state. Quantitative characterization of the integrin dynamic allostery events would greatly advance our understanding of integrin biology, open new doors to elaborate integrin evolutionary adaptations to different functions and would be powerful in enabling both more efficient protein engineering with multiple functional outputs and effector design. This project is funded by the Molecular Biophysics Cluster in the Division of Molecular and Cellular Biosciences. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.