Insights into mRNA export-linked molecular mechanisms of human disease through a Gle1 structure–function analysis

Abstract

A critical step during gene expression is the directional export of nuclear messenger (m)RNA through nuclear pore complexes (NPCs) to the cytoplasm. During export, Gle1 in conjunction with inositol hexakisphosphate (IP6) spatially regulates the activity of the DEAD-box protein Dbp5 at the NPC cytoplasmic face. GLE1 mutations are causally linked to the human diseases lethal congenital contracture syndrome 1 (LCCS1) and lethal arthrogryposis with anterior horn cell disease (LAAHD). Here, structure prediction and functional analysis provide strong evidence to suggest that the LCCS1 and LAAHD disease mutations disrupt the function of Gle1 in mRNA export. Strikingly, direct fluorescence microscopy in living cells reveals a dramatic loss of steady-state NPC localization for GFP-gle1 proteins expressed from human gle1 genes harboring LAAHD and LCCS1 mutations. The potential significance of these residues is further clarified by analyses of sequence and predicted structural conservation. This work offers insights into the perturbed mechanisms underlying human LCCS-1 and LAAHD disease states and emphasizes the potential impact of altered mRNA transport and gene expression in human disease.

Structure and Function of the Nuclear Pore Complex Cytoplasmic mRNA Export Platform

“…Our data (Table S3) also indicates that the C-terminus of Nup42 is associated with the C-terminus of Gle1 (Strahm et al, 1999), where the Nup159 N-terminal β-propellers are dynamically associated, with the Nup159 FG regions oriented towards the arms of the Nup84 complex (Figure 6), and Dbp5 physically associated with its ATPase cycle modulators Gle1 and the Nup159 β-propeller (Montpetit et al, 2011; Noble et al, 2011). Strikingly, the residues equivalent to those causing disease states in human Gle1 (Folkmann et al, 2014) all map to sites that anchor the yeast protein to either the Nup82 holo-complex or to Nup42 and Dbp5-Nup159N (Figure 6). These results, taken together with our structural and functional analyses, underscore the importance of the Nup82 complex as a hub for anchoring both the mRNA transport and processing machineries into the heart of the NPC itself, and help explain why this complex is a focus for so many developmental, oncogenic and viral diseases.…”

An amyotrophic lateral sclerosis-linked mutation in GLE1 alters the cellular pool of human Gle1 functional isoforms

“…Mutations that impact the balance in the functional pools of hGle1 or alter the function of both hGle1 isoforms should have far-reaching impact on mRNA metabolism. The lethal inherited diseases LCCS1 and LAAHD are prime examples of this, wherein mutations that decrease hGle1’s ability to homo-oligomerize or destabilize its structural integrity lead to mRNA export defects that are linked to the arrest of proper development (Nousianen et al, 2008; Folkmann et al, 2013, 2014). …”

Upregulation of <i>GLE</i>1 and <i>LCP</i>2 Genes in H5N1 Influenza Virus Infected Patients

“…The multifunctional Gle1 protein plays an important role in nuclear mRNA export and translation, and mutations in the human GLE1 gene are responsible for the autosomal recessive LCCS1 [15]. Structure prediction and functional analysis suggest that the LCCS1 and lethal arthrogryposis with anterior horn cell disease (LAAHD) mutations disrupt the function of Gle1, indicating the potential impact of altered mRNA transport and gene expression in human diseases [16]. The human LCP2 gene (Gene ID: 3937), also known as SLP-76 (SH2 domain-containing leukocyte protein of 76 kilodaltons) gene, encodes a 76-kDa protein, which was originally identified as a substrate of the ZAP-70 (70-kDa zeta-associated protein kinase) protein tyrosine kinase (PTK) following T cell receptor (TCR) ligation in the leukemic T cell line Jurkat [17]- [19].…”