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Blue light-excited LOV1 and LOV2 domains cooperatively regulate the kinase activity of full-length phototropin2 from Arabidopsis.

ABSTRACT: Phototropin2 (phot2) is a blue-light (BL) receptor that regulates BL-dependent activities for efficient photosynthesis in plants. phot2 comprises two BL-receiving light-oxygen-voltage-sensing domains (LOV1 and LOV2) and a kinase domain. BL-excited LOV2 is thought to be primarily responsible for the BL-dependent activation of the kinase. However, the molecular mechanisms by which small BL-induced conformational changes in the LOV2 domain are transmitted to the kinase remain unclear. Here, we used full-length wild-type and mutant phot2 proteins from Arabidopsis to study their molecular properties in the dark and under BL irradiation. Phosphorylation assays and absorption measurements indicated that the LOV1 domain assists the thermal relaxation of BL-excited LOV2 and vice versa. Using small-angle X-ray scattering and electron microscopy, we observed that phot2 forms a dimer and has a rod shape with a maximum length of 188 Å and a radius of gyration of 44 Å. Under BL, phot2 displayed large conformational changes that bent the rod shape. By superimposing the crystal structures of the LOV1 dimer, LOV2, and a homology model of the kinase to the observed changes, we inferred that the BL-dependent change consisted of positional shifts of both LOV2 and the kinase relative to LOV1. Furthermore, phot2 mutants lacking the photocycle in LOV1 or LOV2 still exhibited conformational changes under BL, suggesting that LOV1 and LOV2 cooperatively contribute to the conformational changes that activate the kinase. These results suggest that BL-activated LOV1 contributes to the kinase activity of phot2. We discuss the possible intramolecular interactions and signaling mechanisms in phot2.

SUBMITTER: Oide M

PROVIDER: S-EPMC5777267 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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Blue light-excited LOV1 and LOV2 domains cooperatively regulate the kinase activity of full-length phototropin2 from <i>Arabidopsis</i>.

Oide Mao M Okajima Koji K Nakagami Hirofumi H Kato Takayuki T Sekiguchi Yuki Y Oroguchi Tomotaka T Hikima Takaaki T Yamamoto Masaki M Nakasako Masayoshi M

The Journal of biological chemistry 20171201 3

Phototropin2 (phot2) is a blue-light (BL) receptor that regulates BL-dependent activities for efficient photosynthesis in plants. phot2 comprises two BL-receiving light-oxygen-voltage-sensing domains (LOV1 and LOV2) and a kinase domain. BL-excited LOV2 is thought to be primarily responsible for the BL-dependent activation of the kinase. However, the molecular mechanisms by which small BL-induced conformational changes in the LOV2 domain are transmitted to the kinase remain unclear. Here, we used ...[more]

PMID: 29196607

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Project description:IntroductionNeurofibrillary tangles (NFT) composed of Tau are hallmarks of neurodegeneration in Alzheimer disease. Transgenic mice expressing full-length pro-aggregant human Tau (2N4R Tau-ΔK280, termed Tau(ΔK)) or its repeat domain (TauRD-ΔK280, TauRD(ΔK)) develop a progressive Tau pathology with missorting, phosphorylation, aggregation of Tau, loss of synapses and functional deficits. Whereas TauRD(ΔK) assembles into NFT concomitant with neuronal death, Tau(ΔK) accumulates into Tau pretangles without overt neuronal loss. Both forms cause a comparable cognitive decline (with onset at 10mo and 12mo, respectively), which is rescued upon switch-off of transgene expression. Since methylene blue (MB) is able to inhibit Tau aggregation in vitro, we investigated whether MB can prevent or rescue Tau-induced cognitive impairments in our mouse models. Both types of mice received MB orally using different preventive and therapeutic treatment protocols, initiated either before or after disease onset. The cognitive status of the mice was assessed by behavior tasks (open field, Morris water maze) to determine the most successful conditions for therapeutic intervention.ResultsPreventive and therapeutic MB application failed to avert or recover learning and memory deficits of TauRD(ΔK) mice. Similarly, therapeutic MB treatment initiated after onset of cognitive impairments was ineffective in Tau(ΔK) mice. In contrast, preventive MB application starting before onset of functional deficits preserved cognition of Tau(ΔK) mice. Beside improved learning and memory, MB-treated Tau(ΔK) mice showed a strong decrease of insoluble Tau, a reduction of conformationally changed (MC1) and phosphorylated Tau species (AT180, PHF1) as well as an upregulation of protein degradation systems (autophagy and proteasome). This argues for additional pleiotropic effects of MB beyond its properties as Tau aggregation inhibitor.ConclusionsOur data support the use of Tau aggregation inhibitors as potential drugs for the treatment of AD and other tauopathies and highlights the need for preventive treatment before onset of cognitive impairments.

Dataset Information

Blue light-excited LOV1 and LOV2 domains cooperatively regulate the kinase activity of full-length phototropin2 from Arabidopsis.

Publications

Blue light-excited LOV1 and LOV2 domains cooperatively regulate the kinase activity of full-length phototropin2 from <i>Arabidopsis</i>.

Similar Datasets

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