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Diversity of oligomerization in Drosophila semaphorins suggests a mechanism of functional fine-tuning.

ABSTRACT: Semaphorin ligands and their plexin receptors are one of the major cell guidance factors that trigger localised changes in the cytoskeleton. Binding of semaphorin homodimer to plexin brings two plexins in close proximity which is a prerequisite for plexin signalling. This model appears to be too simplistic to explain the complexity and functional versatility of these molecules. Here, we determine crystal structures for all members of Drosophila class 1 and 2 semaphorins. Unlike previously reported semaphorin structures, Sema1a, Sema2a and Sema2b show stabilisation of sema domain dimer formation via a disulfide bond. Unexpectedly, our structural and biophysical data show Sema1b is a monomer suggesting that semaphorin function may not be restricted to dimers. We demonstrate that semaphorins can form heterodimers with members of the same semaphorin class. This heterodimerization provides a potential mechanism for cross-talk between different plexins and co-receptors to allow fine-tuning of cell signalling.

SUBMITTER: Rozbesky D

PROVIDER: S-EPMC6695400 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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Diversity of oligomerization in Drosophila semaphorins suggests a mechanism of functional fine-tuning.

Rozbesky Daniel D Robinson Ross A RA Jain Vitul V Renner Max M Malinauskas Tomas T Harlos Karl K Siebold Christian C Jones E Yvonne EY

Nature communications 20190815 1

Semaphorin ligands and their plexin receptors are one of the major cell guidance factors that trigger localised changes in the cytoskeleton. Binding of semaphorin homodimer to plexin brings two plexins in close proximity which is a prerequisite for plexin signalling. This model appears to be too simplistic to explain the complexity and functional versatility of these molecules. Here, we determine crystal structures for all members of Drosophila class 1 and 2 semaphorins. Unlike previously report ...[more]

PMID: 31417095

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Project description:The roles of SUMOylation and the related enzymes in autophagic regulation are unclear. Based on our previous studies that identified the SUMO2/3-specific peptidase SENP3 as an oxidative stress-responsive molecule, we investigated the correlation between SUMOylation and macroautophagy/autophagy. We found that Senp3± mice showed increased autophagy in the liver under basal and fasting conditions, compared to Senp3+/+ mice. We constructed a liver-specific senp3 knockout mouse; these Senp3-deficient liver tissues showed increased autophagy as well. Autophagic flux was accelerated in hepatic and other cell lines following knockdown of SENP3, both before and after the cells underwent starvation in the form of the serum and amino acid deprivation. We demonstrated that BECN1/beclin 1, the core molecule of the BECN1-PIK3C3 complex, could be SUMO3-conjugated by PIAS3 predominantly at K380 and deSUMOylated by SENP3. The basal SUMOylation of BECN1 was increased upon cellular starvation, which enhanced autophagosome formation by facilitating BECN1 interaction with other complex components UVRAG, PIK3C3 and ATG14, thus promoting PIK3C3 activity. In contrast, SENP3 deSUMOylated BECN1, which impaired BECN1-PIK3C3 complex formation or stability to suppress the PIK3C3 activity. DeSUMOylation of BECN1 restrained autophagy induction under basal conditions and especially upon starvation when SENP3 had accumulated in response to the increased generation of reactive oxygen species. Thus, while reversible SUMOylation regulated the degree of autophagy, SENP3 provided an intrinsic overflow valve for fine-tuning autophagy induction.AbbreviationsAL: autolysosome; AP: autophagosome; ATG: autophagy related; ATG14: autophagy related 14; BECN1: beclin 1, autophagy related; cKO: conditional knockout; co-IP: co-immunoprecipitation; CQ: chloroquine; EBSS: Earle's balanced salt solution; GFP: green fluorescent protein; MAP1LC3/LC3: microtubule-associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; NAC: N-acetyl-L-cysteine; PIK3C3: phosphatidylinositol 3-kinase catalytic subunit type 3; PTM: post-translational modification; RFP: red fluorescent protein; ROS: reactive oxygen species; RUBCN/rubicon: RUN domain and cysteine-rich domain containing, BECN1-interacting protein; SENP3: SUMO specific peptidase 3; shRNA: small hairpin RNA; siRNA: small interfering RNA; SQSTM1: sequestosome 1; SUMO: small ubiquitin-like modifier; UVRAG: UV radiation resistance associated gene.

Dataset Information

Diversity of oligomerization in Drosophila semaphorins suggests a mechanism of functional fine-tuning.

Publications

Diversity of oligomerization in Drosophila semaphorins suggests a mechanism of functional fine-tuning.

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