A nuclear localization signal is required for the nuclear translocation of Fign and its microtubule‑severing function

Abstract

It is commonly known that the specific function of a given ATPase associated with diverse cellular activities protein (i.e., a member of the AAA superfamily of proteins) depends primarily on its subcellular location. The microtubule-severing protein fidgetin (Fign) possesses a nuclear localization signal (NLS) that facilitates its translocation to the nucleus, where its assembly is finalized; here, Fign contributes to the regulation of microtubule configuration by cutting and trimming microtubule polymers. In the present study, Fign was found to be a nuclear protein, whose N-terminal sequence (SSLKRKAFYM; residues 314-323) acts as an NLS. Following substitution (KR to NN; 317-318) or deletion (NT; 314-323) mutations within the NLS, Fign, which is predominantly expressed in the nucleus, was found to reside in the cytoplasm of transfected cells. Furthermore, Fign was found to have an essential role in microtubule severing by preferentially targeting highly-tyrosinated microtubules (tyr-MTs). Mutation of the Fign NLS did not affect its microtubule-severing function or the cleavage of tyr-MTs, but did affect the cellular distribution of the Fign protein itself. Taken altogether, an NLS for Fign was identified, and it was demonstrated that the basic amino acids K317 and R318 are necessary for regulating its entry into the nucleus, whereas an increase in Fign in the cytosol due to mutations of the NLS did not affect its cleavage function.

Fidgetin as a potential prognostic biomarker for hepatocellular carcinoma

“…FIGN, a member of the AAA (ATPase associate with diverse cellular activities) family [16], is predominantly localized in the nucleus via its bipartite nuclear localization signal in the central region [7,17,18]. In concordance with previous studies, we observed that FIGN was positively overexpressed in nucleus in human HCC tissues.…”

Protein Delivery to Insect Epithelial Cells In Vivo: Potential Application to Functional Molecular Analysis of Proteins in Butterfly Wing Development

“…Among the antibodies used in this study, anti-tubulin antibodies may have interacted with α-tubulin molecules. Higher-resolution fluorescent images of anti-tubulin antibodies in other studies suggest perinuclear and mesh-like intracellular structures [ 58 , 59 ].…”

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

“…Two other family members were also identified as fidgetin‐like 1 (FL1) and fidgetin‐like 2 (FL2) (Bailey et al, 2016; Cox et al, 2000). The fidgetins generally share the same structure: an N‐terminal NLS (Li et al, 2020; Onitake et al, 2012; Yang et al, 2005), an MIT domain that binds to the microtubule lattice (L'Hôte et al, 2011; Li et al, 2020), a AAA+ ATPase domain (Atkins et al, 2019; Cox et al, 2000; L'Hôte et al, 2011; Li et al, 2020; Yakushiji et al, 2006), and a C‐terminal Vps4 insertion of largely unknown function (L'Hôte et al, 2011; Yuan & Chen, 2013).…”