mRNA Localization and Local Translation of the Microtubule Severing Enzyme, Fidgetin-Like 2, in Polarization, Migration and Outgrowth

Abstract

Cell motility requires strict spatiotemporal control of protein expression. During cell migration, mRNA localization and local translation in subcellular areas like the leading edge and protrusions are particularly advantageous for regulating the reorganization of the cytoskeleton. Fidgetin-Like 2 (FL2), a microtubule severing enzyme (MSE) that restricts migration and outgrowth, localizes to the leading edge of protrusions where it severs dynamic microtubules. FL2 is primarily expressed during development but in adulthood, is spatially upregulated at the leading edge minutes after injury. Here, we show mRNA localization and local translation in protrusions of polarized cells are responsible for FL2 leading edge expression after injury. The data suggests that the RNA binding protein IMP1 is involved in the translational regulation and stabilization of FL2 mRNA, in competition with the miRNA let-7. These data exemplify the role of local translation in microtubule network reorganization during migration and elucidate an unexplored MSE protein localization mechanism.

The fidgetin family: Shaking things up among the microtubule‐severing enzymes

“…Translational regulation is another area that has provided insight into why some MSEs are only expressed under certain conditions. Our lab has found that wild‐type levels of FL2 protein in many adult cells under static conditions is low (R. L. Birnbaum, 2023); however, FL2 protein expression locally increases at the cell edge after injury to a monolayer, which was shown to be mediated by local translation in cells on the wound periphery (R. Birnbaum et al, 2023; R. L. Birnbaum, 2023). FL2 mRNA similarly localized to the leading edge of cells, suggesting the involvement of local protein synthesis in response to the injury.…”

“…Investigation into the RNA‐binding proteins (RBP) that mediated this mRNA localization suggests that the RBPs IMP1 and IMP2 are involved in this process. RBPs bind mRNAs to control their subcellular localization, local translation, and degradation, thereby tightly regulating their local and temporal expression (R. Birnbaum et al, 2023; R. L. Birnbaum, 2023).…”

“…Regulation of local FL2 mRNA translation may thus be due to a tight balance between IMP‐mediated transport to the leading edge, let‐7 miRNA‐mediated FL2 mRNA degradation, and Lin28A inhibition of let‐7 activity (R. Birnbaum et al, 2023; R. L. Birnbaum, 2023). Potential binding sites for IMP1 and IMP2 were also found in fidgetin and FL1, as well as katanin and spastin (R. Birnbaum et al, 2023; R. L. Birnbaum, 2023), indicating that spatial and temporal control of protein expression is an unexplored regulatory mechanism across the MSE families. Altogether, these findings warrant further investigation into the role of translational regulation in the activity and localization of the fidgetin family members and indeed even the other MSEs.…”

“…Our lab has found that wild-type levels of FL2 protein in many adult cells under static conditions is low (R. L. Birnbaum, 2023); however, FL2 protein expression locally increases at the cell edge after injury to a monolayer, which was shown to be mediated by local translation in cells on the wound periphery (R. Birnbaum et al, 2023;R. L. Birnbaum, 2023).…”

“…Regulation of local FL2 mRNA translation may thus be due to a tight balance between IMP-mediated transport to the leading edge, let-7 miRNA-mediated FL2 mRNA degradation, and Lin28A inhibition of let-7 activity (R. Birnbaum et al, 2023;R. L. Birnbaum, 2023).…”