NETWORKED 3B: a novel protein in the actin cytoskeleton-endoplasmic reticulum interaction.

Pengwei Wang,Patrick J Hussey

doi:10.1093/jxb/erx047

Pengwei Wang, Patrick J Hussey

Open Access

https://doi.org/10.1093/jxb/erx047

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Abstract

In plants movement of the endoplasmic reticulum (ER) is dependent on the actin cytoskeleton. However little is known about proteins that link the ER membrane and the actin cytoskeleton. Here we identified a novel protein, NETWORKED 3B (NET3B), which is associated with the ER and actin cytoskeleton in vivo. NET3B belongs to a superfamily of plant specific actin binding proteins, the NETWORKED family. NET3B associates with the actin cytoskeleton in vivo through an N-terminal NET actin binding (NAB) domain, which has been well-characterized in other members of the NET family. A three amino acid insertion, Val-Glu-Asp, in the NAB domain of NET3B appears to lower its ability to localize to the actin cytoskeleton compared with NET1A, the founding member of the NET family. The C-terminal domain of NET3B links the protein to the ER. Overexpression of NET3B enhanced the association between the ER and the actin cytoskeleton, and the extent of this association was dependent on the amount of NET3B available. Another effect of NET3B overexpression was a reduction in ER membrane diffusion. In conclusion, our results revealed that NET3B modulates ER and actin cytoskeleton interactions in higher plants.

Highlights

Remodelling of the endoplasmic reticulum (ER) in plants is mainly dependent on the actin cytoskeleton (Boevink et al, 1998; Sparkes et al, 2009)
We show that the NET actin binding (NAB) domain of NETWORKED 3B (NET3B) is unique amongst the NET superfamily due to the insertion of three amino acids, ValGlu-Asp (Hawkins et al, 2014), which affects its ability to co-localize with the actin cytoskeleton in vivo
NET3B-green fluorescent protein (GFP) localized to the ER upon treatment with latrunculin B, suggesting that localizeNET3B-GFP has the ability to bind to the ER (Fig. 1d)

Summary

Introduction

Remodelling of the endoplasmic reticulum (ER) in plants is mainly dependent on the actin cytoskeleton (Boevink et al, 1998; Sparkes et al, 2009). When overexpressing NET3B-GFP, the ER network and actin cytoskeleton showed clear co-localization (Fig. 1e). Few ER cisternae were observed when NET3B-GFP was overexpressed and some parts of the ER network appeared to follow the pattern and organization of the NET3B-GFP-labelled actin cytoskeleton (Fig. 1e).

Results

Conclusion