The effect of hypusine modification on the intracellular localization of eIF5A

Abstract

Eukaryotic translation initiation factor 5A (eIF5A) is a highly conserved protein essential for eukaryotic cell proliferation and is the only protein containing hypusine, [N ε -(4-amino-2-hydroxybutyl)lysine]. eIF5A is activated by the posttranslational synthesis of hypusine. eIF5A also undergoes an acetylation at specific Lys residue(s). In this study, we have investigated the effect of hypusine modification and acetylation on the subcellular localization of eIF5A. Immunocytochemical analyses showed differences in the distribution of non-hypusinated eIF5A precursor and the hypusine-containing mature eIF5A. While the precursor is found in both cytoplasm and nucleus, the hypusinated eIF5A is primarily localized in cytoplasm. eIF5A mutant proteins, defective in hypusine modification (K50A, K50R) were localized in a similar manner to the eIF5A precursor, whereas hypusine-modified mutant proteins (K47A, K47R, K68A) were localized mainly in the cytoplasm. These findings provide strong evidence that the hypusine modification of eIF5A dictates its localization in the cytoplasmic compartment where it is required for protein synthesis.

Deoxyhypusine synthase haploinsufficiency attenuates acute cytokine signaling

“…With regard to the islet β cell, hypusination may be an especially attractive target for several reasons: (1) hypusinated eIF5A has a very short half-life in islets (~6 h), 22 compared to other cell types (>20 h), 22,[34][35][36] a finding supporting an acute regulatory role for the protein in islets; (2) eIF5A and DHS exhibit rapid and reciprocal nucleo-cytoplasmic shuttling in β cells in response to cytokines or ER stress, 14,22 whereas in other cell types specific compartmentation is less clear or controversial; 20,37 and (3) the islet β cell has a very slow replicative rate and therefore is less susceptible acutely to agents (such as DHS inhibitors) that affect cellular proliferation. Because our data suggest that Dhps +/-mice can maintain normal growth and glucose homeostasis, with evidence that their cells maintain more robust responses to inflammation, we feel that pharmacologic approaches to inhibiting DHS could be successful in mitigating diabetes progression in an intact animal.…”

Rapid proteomic responses to a near-lethal heat stress in the salt marsh musselGeukensia demissa

“…8), are more difficult to categorize. Although the function of eIF5A is not completely understood, the protein either is found in the cytosol, where its activity as an elongation factor is required for cell proliferation, or it localizes to the nucleus and helps regulate apoptosis, depending on the presence or absence of a unique hypusine PTM (Caraglia et al, 2001;Lee et al, 2009). Interestingly, decreased levels of active (hypusinated) eIF5A inhibit cell growth (Nishimura et al, 2005), and we propose that the changes in eIF5A we have found in G. demissa at 24 h may indicate a relief of that inhibition as gill recovers from heat stress.…”

Cloning and expression analysis ofeIF-5Agene inApocynum venetum

“…Hypusine eIF-5A is known to interact with components of the 80S ribosome and translation elongation factors 2 in a hypusine-dependent manner. [1,2] eIF-5A was originally isolated from immature red blood cells and was identified as a translation initiation factor, [3] but recent research suggests that the activity of eIF-5A is not absolutely essential for general protein biosynthesis. The role of eIF-5A in translation is to act as a nucleocytoplasmic shuttle protein that selectively translocates specific subsets of mRNAs from the nucleus to the cytoplasm.…”