Molecular and cellular mechanisms in elastic nanofiber formation

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The formation of elastic fibers, termed elastogenesis, is a fundamental process in biology, conferring elasticity to several vital organs, such as blood vessels, lung, and skin. It is a process that depends on hierarchical assembly mechanisms of many individual components. The overarching long-term goal of the Discovery program is to decipher the properties of essential components in this process and their functional relationships with each other and with cells. It aims to determine how these mechanisms lead to formation of fully functional elastic fibers on the nanoscale level. Despite some important advances in understanding the functional relationships between elastogenic proteins, the critical underlying protein-protein and protein-cell interactions that drive elastic nanofiber assembly are still elusive. The short-term goals for the next five-year grant cycle focus on determining the role of three accessory proteins in elastic nanofiber formation, microfibrillar associated glycoprotein 4 (MFAP4), fibulin-4, and latent transforming growth factor binding protein 4 (LTBP4). MFAP4 localizes to and is associated with elastic fibers, but its role in elastic fiber biogenesis remains unclear. Fibulin-4 and LTBP4 are critical accessory proteins in elastogenesis, and we have recently identified key functional relationships between these proteins necessary for proper elastogenesis. We identified that multimerization of fibulin-4 is essential for cell interaction and determined cell surface proteoglycans as receptors for both proteins. Using a series of biophysical and cell culture methods, we aim to reveal important mechanistic information on complex formation of these three proteins, how these complexes interact with other elastogenic proteins, the cellular consequences, and the role in elastic nanofiber formation. In aim 1, we propose to define the structure, self-association, and oligomerization of MFAP4, and determine its significance in elastogenesis. In aim 2, we aim to study the functional relationship of protein complex formation of MFAP4, fibulin-4 and LTBP4. We also will analyze the functional consequences of complex formation on cell interactions, elastic nanofiber formation, cell function and contractility, and on extracellular matrix remodeling. We expect that this Discovery research program will provide novel fundamental knowledge and molecular mechanisms on the hierarchical processes in elastogenesis. The program will provide graduate students and postdoctoral fellows with skill sets needed for positions in academia and in the Canadian biotechnology sector. We predict that it will reveal new avenues to produce synthetic elastic nanofibers and advanced nanomaterials.