Identification of New Potential Interaction Partners for Human Cytoplasmic Copper Chaperone Atox1: Roles in Gene Regulation?

Helena Öhrvik,Pernilla Wittung-Stafshede

doi:10.3390/ijms160816728

Helena Öhrvik, Pernilla Wittung-Stafshede

Open Access

https://doi.org/10.3390/ijms160816728

Copy DOI

Abstract

The human copper (Cu) chaperone Atox1 delivers Cu to P1B type ATPases in the Golgi network, for incorporation into essential Cu-dependent enzymes. Atox1 homologs are found in most organisms; it is a 68-residue ferredoxin-fold protein that binds Cu in a conserved surface-exposed Cys-X-X-Cys (CXXC) motif. In addition to its well-documented cytoplasmic chaperone function, in 2008 Atox1 was suggested to have functionality in the nucleus. To identify new interactions partners of Atox1, we performed a yeast two-hybrid screen with a large human placenta library of cDNA fragments using Atox1 as bait. Among 98 million fragments investigated, 25 proteins were found to be confident interaction partners. Nine of these were uncharacterized proteins, and the remaining 16 proteins were analyzed by bioinformatics with respect to cell localization, tissue distribution, function, sequence motifs, three-dimensional structures and interaction networks. Several of the hits were eukaryotic-specific proteins interacting with DNA or RNA implying that Atox1 may act as a modulator of gene regulation. Notably, because many of the identified proteins contain CXXC motifs, similarly to the Cu transport reactions, interactions between these and Atox1 may be mediated by Cu.

Highlights

Cu is found in the active sites of essential proteins that participate in cellular reactions such as respiration, antioxidant defense, neurotransmitter biosynthesis, connective-tissue biosynthesis and pigment formation [1,2,3]
The 68-residue antioxidant 1 copper chaperone (Atox1) picks up Cu that has entered the cell via the membrane-bound Cu importer Ctr1 and delivers the metal to cytoplasmic metal-binding domains in
Because Atox1 was proposed to have functionality outside of the cytoplasm [18,19,20], and we as well as others have detected it in the nucleus [21,22], we were captivated to explore the cellular interaction network for Atox1

Summary

Introduction

Cu is found in the active sites of essential proteins that participate in cellular reactions such as respiration, antioxidant defense, neurotransmitter biosynthesis, connective-tissue biosynthesis and pigment formation [1,2,3]. The redox ability (switch between Cu+ and Cu2+) of Cu allows Cu-containing proteins to play important roles as electron carriers and redox catalysts in living systems. To avoid toxicity of Cu+, the intracellular concentration of Cu is regulated via dedicated proteins that facilitate its uptake, efflux, as well as distribution to target Cu-dependent proteins and enzymes [4,5,6]. The 68-residue antioxidant 1 copper chaperone (Atox1) picks up Cu that has entered the cell via the membrane-bound Cu importer Ctr and delivers the metal to cytoplasmic metal-binding domains in ATP7A and ATP7B ( called Menke’s and Wilson disease proteins, respectively), two homologous multi-domain P1B-type ATPases located in the trans-Golgi network. Many human copper-dependent enzymes acquire Cu from these ATPases before reaching their final destination in the body [4,5,6]. Atox contains an apparent nuclear localization sequence (NLS) KKTGK within its C-terminal part and, not discussed, in the initial discovery paper of

Methods

Results

Conclusion