Regulatory functions of a plant TSPO-related protein during abiotic stress
(2018)
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- Authors
- Supervisors
- Batoko, Henri
- Abstract
- Translocator proteins (TSPO) are evolutionarily conserved polytopic membrane proteins. Structurally, they share a core transmembrane domain made of five α-helices. However, the length and structure of their termini appear to be kingdom-specific. After more than forty years of extensive studies, the biological role of TSPO is still highly discussed. It seems that, from bacteria to humans, these nonessential proteins are upregulated during cellular stresses to sense and regulate redox homeostasis through tetrapyrrole metabolism. The molecular mechanism of this ancient regulatory role persists nowadays with variations from species to species. In addition, recent evidences in animal cells suggest that TSPO may modulate lipid metabolism. The Arabidopsis thaliana TSPO (AtTSPO) is an abiotic stress-induced membrane protein with a plant-specific polybasic N-terminal extension. In particular, AtTSPO is highly induced by osmotic stress. The presence of AtTSPO in the cell is tightly regulated and the degradation of AtTSPO requires heme binding and an active autophagy pathway. AtTSPO physically interacts with the plasma membrane aquaporin PIP2;7 in vivo and targets the aquaporin for autophagic degradation during osmotic stress. In this work, we present evidence supporting a role for plant TSPO in the cell energy homeostasis in a tissue-specific manner. We showed that AtTSPO can enhance fatty acids and lipid droplets (LD) accumulation in mature seeds but limiting LD levels in seedlings. Moreover, we show that AtTSPO binds the signaling lipid PI(4,5)P2 through its N-terminal polybasic extension. The N-terminus extension of AtTSPO can also mistarget a PI(4,5)P2 biosensor from the plasma membrane to the Golgi membranes where AtTSPO is localized in the plant cell. Deletion of the N-terminus, or defined point mutations within, prevented AtTSPO-PIP2;7 interaction in vivo. These findings support a functional divergence of plant TSPO from their bacterial and animal counterparts, through the evolutionary acquisition of a lipid-interacting N-terminal extension.
- Affiliations
Citations
Jurkiewicz, P. K. (2018). Regulatory functions of a plant TSPO-related protein during abiotic stress. https://hdl.handle.net/2078.5/125398