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Regulation of Selective autophagy by sulfide through persulfidation of protein targets.

Periodic Reporting for period 1 - SSHelectPhagy (Regulation of Selective autophagy by sulfide through persulfidation of protein targets.)

Reporting period: 2019-06-15 to 2020-06-14

SSHelectphagy project aims at gaining a solid understanding of autophagy regulation in plants, since the regulation of selective autophagy by sulfide has not been previously addressed. In plants, autophagy is critically important in many aspects of plant life, including seedling establishment, plant development, stress resistance, metabolism and reproduction. Autophagy was initially characterized as a bulk degradation pathway with a role in nutrient recycling, but it also contributes to intracellular homeostasis in cells by selectively degrading aggregated proteins, damaged mitochondria, ribosomes, toxic macromolecules, excess peroxisomes, and pathogens to prevent toxicity. This selective autophagy is mediated by the binding of adaptor proteins, which links a cargo targeted for degradation to the autophagosome machinery. ATG18a is a core autophagy component required for reticulophagy during ER stress, and recently it was published its susceptibility to be modified by persulfidation. We, therefore, hypothesize that persulfidation of ATG18a regulates ER stress–induced autophagy in Arabidopsis. So, the overall aim of this project is to shed light to the role of sulfide in the regulation of selective autophagy under ER stress.
To test this hypothesis, we propose the following objectives:
O1.1. Study the role of sulfide in ER stress. Functional analysis of ATG18a in vitro.
O1.2. Study of the physiological effects of sulfide under ER stress conditions in Arabidopsis.
O1.3. Functional analysis of persulfidation of ATG18a in ER stress
Within the field of the plant, the research developed may have an impact on improvement of crop productivity and adaptation mechanisms of plants against adverse environmental conditions. Although this project has focused on plants, this research has a strong influence not only in plant systems but also in other eukaryotic systems.
Most of the tasks described in the proposal have been accomplished. As a summary, the role of sulfide in the regulation of ATG18a by persulfidation has been deciphered (milestone 1, M-1) and the effect of sulfide in autophagy under ER stress has been determined (M-2). Results obtained have been disseminated in international workshops and other meetings such as outreach activities, and multimedia releases (D-1.2 D-2.2) described in detail in this report. This report includes a description of the identification of cysteine residue modified by persulfidation and the effect of this modification on ATG18a activity (Deliverable1.1 D-1.1) and the physiological effect of sulfide in autophagy during ER stress (D-2.1). This report also includes preliminary results for the functional effect of persulfidation on ATG18a in ER stress in vivo (D-3.1) but further microscopy experiments are needed for a robust conclusion. Due to pandemic concerns, milestone-3 and Deliverables-3.1 and D-3.2 have been delayed, which is also described in this report.
Task achieved and results dissemination is further detailed in the Technical report.
Sulfide has been proposed in several publications to regulate autophagy in mammals, while in plants it has been recently suggested to be involved in autophagy regulation. Nevertheless, no previous experiments have been performed to reveal this regulation through persulfidation. Besides, no previous research has been focused on regulation of selective autophagy through sulfide.
We will highlight for the first time in plant systems the regulation of selective autophagy, reticulophagy and mitophagy, by sulfide as a signaling molecule.
The front-line knowledge generated in SSHelectPhagy will be used for further research via horizontal transfer, since this innovative research can be of great importance in other eukaryotic systems such as mammals, where this regulation will determine new targets for further studies, including several important human diseases, such as neurodegenerative diseases and cancer.
SSHelectPhagy will contribute to advancing our knowledge of autophagy signaling in response to external stresses, which will allow improving crop yields, which may potentially save billions of Euros worldwide. Overall, the proposed project will create new knowledge leading to a great advancement of this field and will enhance the attractiveness of this signaling mechanism to the scientific community.