Tubulin modifications and cytoskeletal alterations in aging - Project Summary Remarkably, our understanding of the mechanisms that lead to cytoskeletal alterations and the phenotypic impact of these alterations in aging cells remains very limited. We have identified and begun characterizing key proteins required to maintain normal nuclear morphology, including two novel proteins (LRRC49 and C11orf49) that assemble into a tubulin poly-glutamylase (TPG) complex. We have recently shown that each protein regulates both tubulin glutamylation and nuclear morphology, and ablation of these genes alters post- translational modifications (PTM) of tubulin, cytoskeletal networks, and nuclear shape. Since similar cytoskeletal and nuclear defects are also observed in cells obtained from patients with the premature aging syndrome, Hutchinson-Gilford progeria syndrome (HGPS), this prompted us to hypothesize that specific defects in PTMs and microtubule networks could be associated with aging. Furthermore, it is known that levels of SUN1, a component of the LINC (Linkers of Nucleoskeleton and Cytoskeleton) complex that connects the cytoskeleton and the nucleoskeleton, are altered during normal and premature aging. However, it is unknown whether altered SUN1 levels are a cause or consequence of aging. We will pursue two Aims that combine biochemical and cell biological approaches to (1) investigate a global role for defects in microtubule networks and alterations in tubulin glutamylation and SUN1 levels during physiological aging and in progeroid cells, and (2) identify how defects associated with normal and premature aging are translated into genome-wide changes in chromatin topology. Here, we will specifically focus on how the TPG and SUN1 protein globally regulate microtubule networks and nuclear assembly during aging. Our studies will address fundamental questions related to the role of SUN1 and tubulin modifications in nuclear shape changes and in physiological and pathological models of aging, and our studies will determine whether these alterations are a cause or consequence of aging. Our studies will also provide insights into the changes in chromatin topology sustained by cells that age through normal or pathological mechanisms.
