Identification of a novel lipin homologue from the parasitic protozoan Trypanosoma brucei

Michel Pelletier,Jeff J Sattora,Dominic N Munini,Jenna M Wiemer,Alyssa S Frainier,Amber R Karpie

doi:10.1186/1471-2180-13-101

Abstract

BackgroundArginine methylation is a post-translational modification that expands the functional diversity of proteins. Kinetoplastid parasites contain a relatively large group of protein arginine methyltransferases (PRMTs) compared to other single celled eukaryotes. Several T. brucei proteins have been shown to serve as TbPRMT substrates in vitro, and a great number of proteins likely to undergo methylation are predicted by the T. brucei genome. This indicates that a large number of proteins whose functions are modulated by arginine methylation await discovery in trypanosomes. Here, we employed a yeast two-hybrid screen using as bait the major T. brucei type I PRMT, TbPRMT1, to identify potential substrates of this enzyme.ResultsWe identified a protein containing N-LIP and C-LIP domains that we term TbLpn. These domains are usually present in a family of proteins known as lipins, and involved in phospholipid biosynthesis and gene regulation. Far western and co-immunoprecipitation assays confirmed the TbPRMT1-TbLpn interaction. We also demonstrated that TbLpn is localized mainly to the cytosol, and is methylated in vivo. In addition, we showed that, similar to mammalian and yeast proteins with N-LIP and C-LIP domains, recombinant TbLpn exhibits phosphatidic acid phosphatase activity, and that two conserved aspartic acid residues present in the C-LIP domain are critical for its enzymatic activity.ConclusionsThis study reports the characterization of a novel trypanosome protein and provides insight into its enzymatic activity and function in phospholipid biosynthesis. It also indicates that TbLpn functions may be modulated by arginine methylation.

Highlights

Arginine methylation is a post-translational modification that expands the functional diversity of proteins
Consistent with the yeast-two-hybrid data, we show that TbLpn interacts in vivo with TbPRMT1, and that it is methylated on arginine residues in vivo
Identification of TbLpn as a TbPRMT1-interacting protein To begin to understand the functions of protein arginine methylation in trypanosomes, we sought to identify proteins that interact with the major type I protein arginine methyltransferases (PRMTs) in T. brucei, TbPRMT1

Summary

Introduction

Arginine methylation is a post-translational modification that expands the functional diversity of proteins. Several T. brucei proteins have been shown to serve as TbPRMT substrates in vitro, and a great number of proteins likely to undergo methylation are predicted by the T. brucei genome This indicates that a large number of proteins whose functions are modulated by arginine methylation await discovery in trypanosomes. Catalysis of arginine methylation is carried out by a family of enzymes termed protein arginine methyltransferases [PRMTs). While these enzymes are apparently absent from prokaryotes, putative PRMTs have been identified in the genomes of all eukaryotes examined with the exception of Giardia lamblia [1,25,26]

Methods

Results

Conclusion