Deconstruction of the beaten Path-Sidestep interaction network provides insights into neuromuscular system development.

Hanqing Li,Siamak K Sorooshyari,Kai Zinn,Engin Özkan,Agnieszka Olechwier,Hyung-Kook (Peter) Lee,Mario A Fares,Dermott P Harnett,Michael Anaya,Juan-Pablo Labrador,K Christopher Garcia,Jost Vielmetter,Ash Watson

doi:10.7554/elife.28111

Abstract

An 'interactome' screen of all Drosophila cell-surface and secreted proteins containing immunoglobulin superfamily (IgSF) domains discovered a network formed by paralogs of Beaten Path (Beat) and Sidestep (Side), a ligand-receptor pair that is central to motor axon guidance. Here we describe a new method for interactome screening, the Bio-Plex Interactome Assay (BPIA), which allows identification of many interactions in a single sample. Using the BPIA, we 'deorphanized' four more members of the Beat-Side network. We confirmed interactions using surface plasmon resonance. The expression patterns of beat and side genes suggest that Beats are neuronal receptors for Sides expressed on peripheral tissues. side-VI is expressed in muscle fibers targeted by the ISNb nerve, as well as at growth cone choice points and synaptic targets for the ISN and TN nerves. beat-V genes, encoding Side-VI receptors, are expressed in ISNb and ISN motor neurons.

Highlights

Protein-protein interactions (PPIs) control a vast array of processes in metazoans, ranging from signal transduction and gene regulation within cells to signaling between cells via cell surface and secreted proteins (CSSPs)
Side belongs to an immunoglobulin superfamily (IgSF) subfamily whose origin predates drosophilid speciation Gene duplication, a key phenomenon in the expansion of gene families, provides opportunity for the fine-tuning or innovation of protein interactions and functions (Ohno, 1970)
These observations suggest that beats have undergone two levels of specialization: functional specialization after duplication and emergence of the seven major Beaten Path (Beat) branches, followed by individuation of expression patterns and binding specificities for members of the four subclusters (I, II, III, V)

Summary

Introduction

Protein-protein interactions (PPIs) control a vast array of processes in metazoans, ranging from signal transduction and gene regulation within cells to signaling between cells via cell surface and secreted proteins (CSSPs). The strength of PPIs varies widely, from high-affinity interactions that create stable protein complexes to weak transient interactions (Nooren and Thornton, 2003). Defining global PPI patterns (‘interactomes’) has been the focus of much recent research. Progress has been made in generating high-throughput protein interaction data for a variety of organisms, including S. cerevisiae (Tarassov et al, 2008), C. elegans (Li et al, 2004; Simonis et al, 2009) and D. melanogaster

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