CAREER: Isoform-Dependent Redox Regulation of Actin

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117- 2).Actin is an essential cytoskeletal protein in eukaryotic cells that undergoes reversible monomer-to-polymer transitions. This results in a diverse array of functional configurations, ranging from actin involvement in muscle contraction to synaptic plasticity. To support such variety of functions, actin polymers are continuously disassembled to monomers and reassembled to polymers in a tightly regulated manner. This research is focused on regulation of actin dynamics by a novel reduction/oxidation (redox) mechanism. This mechanism is orchestrated by MICAL enzymes (Molecule Interacting with Cas L) that promote disassembly of actin polymers via targeted oxidation of two conserved amino acids in its sequence which, in turn, can be reversed by Methionine sulfoxide reductases (MsrB/SelR). In its polymer form, actin serves not only as a substrate of Mical but also an activator of a hydrogen peroxide production by these enzymes which potentially can lead to a broader redox signaling in health and disease. Essential cellular processes such as cell division, muscle, heart, and neuronal development require activity of MICAL, however, molecular level understanding of how actin structures in different cell types are impacted by Mical/MsrB redox mechanism is limited and will be addressed by this research. Acquired knowledge will contribute to a more complete understanding of fundamental actin-dependent cellular processes. The Broader Impacts of this work comprise a tight integration of research and education. This project will have a positive impact on development of a competitive STEM workforce, full participation of women, first generation students, and underrepresented minorities in STEM, improved STEM educator development at the level of local increased public scientific literacy via development of a free web resource. American Rescue Plan funding provides support for this investigator at a critical stage in her career.The actin cytoskeleton is indispensable for viability of eukaryotic cell. In mammals, a variety of actin-based structures are built from six different isoforms that are expressed in a cell type-specific manner. How these cytoskeletal structures are differentially regulated based on their actin isoform composition is an open fundamental question. The goal of this project is to understand how dynamics of actin isoforms are differentially regulated by a novel mechanism orchestrated by Mical and MsrB enzymes which involves site-specific oxidation/reduction of two methionines in actin’s sequence. The central hypothesis to be tested is that upon Mical-induced oxidation, actin dynamics, stability, interactions, and activation of Mical-mediated hydrogen peroxide production are actin isoform-dependent. This will be addressed by combining synthetic biology, biochemistry, biophysics, and TIRF imaging, and will allow defining the key features of actin that determine it susceptibility to Mical-induced disassembly and MrsB-driven reassembly. This knowledge will be broadly applicable and allow for prediction of the biological consequences of Mical activation based on the local actin isoform composition. The acquired knowledge will contribute to in-depth understanding of how the Mical/MsrB redox mechanism functions in different cells, tissues, and organisms.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.