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A cytosolic juxtamembrane interface modulates plexin A3 oligomerization and signal transduction.

ABSTRACT: Plexins (plxns) are transmembrane (TM) receptors involved in the guidance of vascular, lymphatic vessel, and neuron growth as well as cancer metastasis. Plxn signaling results in cytosolic GTPase-activating protein activity, and previous research implicates dimerization as important for activation of plxn signaling. Purified, soluble plxn extracellular and cytosolic domains exhibit only weak homomeric interactions, suggesting a role for the plxn TM and juxtamembrane regions in homooligomerization. In this study, we consider a heptad repeat in the Danio rerio PlxnA3 cytosolic juxtamembrane domain (JM) for its ability to influence PlxnA3 homooligomerization in TM-domain containing constructs. Site-directed mutagenesis in conjunction with the AraTM assay and bioluminescent energy transfer (BRET²) suggest an interface involving a JM heptad repeat, in particular residue M1281, regulates PlxnA3 homomeric interactions when examined in constructs containing an ectodomain, TM and JM domain. In the presence of a neuropilin-2a co-receptor and semaphorin 3F ligand, disruption to PlxnA3 homodimerization caused by an M1281F mutation is eliminated, suggesting destabilization of the PlxnA3 homodimer in the JM is not sufficient to disrupt co-receptor complex formation. In contrast, enhanced homodimerization of PlxnA3 caused by mutation M1281L remains even in the presence of ligand semaphorin 3F and co-receptor neuropilin-2a. Consistent with this pattern of PlxnA3 dimerization in the presence of ligand and co-receptor, destabilizing mutations to PlxnA3 homodimerization (M1281F) are able to rescue motor patterning defects in sidetracked zebrafish embryos, whereas mutations that enhance PlxnA3 homodimerization (M1281L) are not. Collectively, our results indicate the JM heptad repeat, in particular residue M1281, forms a switchable interface that modulates both PlxnA3 homomeric interactions and signal transduction.

SUBMITTER: Barton R

PROVIDER: S-EPMC4286236 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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A cytosolic juxtamembrane interface modulates plexin A3 oligomerization and signal transduction.

Barton Rachael R Palacio Danica D Iovine M Kathryn MK Berger Bryan W BW

PloS one 20150107 1

Plexins (plxns) are transmembrane (TM) receptors involved in the guidance of vascular, lymphatic vessel, and neuron growth as well as cancer metastasis. Plxn signaling results in cytosolic GTPase-activating protein activity, and previous research implicates dimerization as important for activation of plxn signaling. Purified, soluble plxn extracellular and cytosolic domains exhibit only weak homomeric interactions, suggesting a role for the plxn TM and juxtamembrane regions in homooligomerizatio ...[more]

PMID: 25565389

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Project description:During embryogenesis motor axons navigate to their target muscles, where individual motor axons develop complex branch morphologies. The mechanisms that control axonal branching morphogenesis have been studied intensively, yet it still remains unclear when branches begin to form or how branch locations are determined. Live cell imaging of individual zebrafish motor axons reveals that the first axonal branches are generated at the ventral extent of the myotome via bifurcation of the growth cone. Subsequent branches are generated by collateral branching restricted to their synaptic target field along the distal portion of the axon. This precisely timed and spatially restricted branching process is disrupted in turnout mutants we identified in a forward genetic screen. Molecular genetic mapping positioned the turnout mutation within a 300 kb region encompassing eight annotated genes, however sequence analysis of all eight open reading frames failed to unambiguously identify the turnout mutation. Chimeric analysis and single cell labeling reveal that turnout function is required cell non-autonomously for intraspinal motor axon guidance and peripheral branch formation. turnout mutant motor axons form the first branch on time via growth cone bifurcation, but unlike wild-type they form collateral branches precociously, when the growth cone is still navigating towards the ventral myotome. These precocious collateral branches emerge along the proximal region of the axon shaft typically devoid of branches, and they develop into stable, permanent branches. Furthermore, we find that null mutants of the guidance receptor plexin A3 display identical motor axon branching defects, and time lapse analysis reveals that precocious branch formation in turnout and plexin A3 mutants is due to increased stability of otherwise short-lived axonal protrusions. Thus, plexin A3 dependent intrinsic and turnout dependent extrinsic mechanisms suppress collateral branch morphogenesis by destabilizing membrane protrusions before the growth cone completes navigation into the synaptic target field.

Dataset Information

A cytosolic juxtamembrane interface modulates plexin A3 oligomerization and signal transduction.

Publications

A cytosolic juxtamembrane interface modulates plexin A3 oligomerization and signal transduction.

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