Roles and Cellular Localization of GBP2 and NAB2 During the Blood Stage of Malaria Parasites.

Mamoru Niikura,Jiro Mitobe,Toshiyuki Fukutomi,Fumie Kobayashi

doi:10.3389/fcimb.2021.737457

Mamoru Niikura, Jiro Mitobe + Show 2 more

Open Access

https://doi.org/10.3389/fcimb.2021.737457

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Abstract

The quality control and export of mRNA by RNA-binding proteins are necessary for the survival of malaria parasites, which have complex life cycles. Nuclear poly(A) binding protein 2 (NAB2), THO complex subunit 4 (THO4), nucleolar protein 3 (NPL3), G-strand binding protein 2 (GBP2) and serine/arginine-rich splicing factor 1 (SR1) are involved in nuclear mRNA export in malaria parasites. However, their roles in asexual and sexual development, and in cellular localization, are not fully understood. In this study using the rodent malaria parasite, Plasmodium berghei, we found that NAB2 and SR1, but not THO4, NPL3 or GBP2, played essential roles in the asexual development of malaria parasites. By contrast, GBP2 but not NPL3 was involved in male and female gametocyte production. THO4 was involved in female gametocyte production, but had a lower impact than GBP2. In this study, we focused on GBP2 and NAB2, which play important roles in the sexual and asexual development of malaria parasites, respectively, and examined their cellular localization. GBP2 localized to both the nucleus and cytoplasm of malaria parasites. Using immunoprecipitation coupled to mass spectrometry (IP-MS), GBP2 interacted with the proteins ALBA4, DOZI, and CITH, which play roles in translational repression. IP-MS also revealed that phosphorylated adapter RNA export protein (PHAX) domain-containing protein, an adaptor protein for exportin-1, also interacted with GBP2, implying that mRNA export occurs via the PHAX domain-containing protein pathway in malaria parasites. Live-cell fluorescence imaging revealed that NAB2 localized at the nuclear periphery. Moreover, IP-MS indicated that NAB2 interacted with transportin. RNA immunoprecipitation coupled to RNA sequencing revealed that NAB2 bound directly to 143 mRNAs, including those encoding 40S and 60S ribosomal proteins. Our findings imply that malaria parasites use an evolutionarily ancient mechanism conserved throughout eukaryotic evolution.

Highlights

Malaria parasites are unicellular eukaryotes that belong to the genus Plasmodium in the phylum Apicomplexa
We first investigated the effects of nab2, tho4, npl3, gbp2 and sr1 deletion on the asexual development of malaria parasites
The courses of parasitemia in mice infected with Dtho4 or Dnpl3 were comparable with those in mice infected with the control or Dgbp2 parasites (Figure 1A)

Summary

Introduction

Malaria parasites are unicellular eukaryotes that belong to the genus Plasmodium in the phylum Apicomplexa. Malaria parasites have complex life cycles, alternating between female Anopheles mosquitoes and vertebrate hosts. The quality control and export of mRNA, as well as the post-transcriptional regulation of gene expression by RNA-binding proteins, play important roles in the life cycles of malaria parasites (Mair et al, 2006; Guerreiro et al, 2014). In Opisthokonta, such as yeast, the mRNA export receptor Mex67/Mtr interacts with nuclear pore complex proteins and plays a pivotal role during the terminal step of nuclear mRNA export (Katahira, 2015; Wickramasinghe and Laskey, 2015; Xie and Ren, 2019). Malaria parasites possess genes encoding all of the adaptor proteins required for Mex67/Mtr recruitment (Tuteja and Mehta, 2010)

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