RRC ID 11393
Author Vanhee C, Guillon S, Masquelier D, Degand H, Deleu M, Morsomme P, Batoko H.
Title A TSPO-related protein localizes to the early secretory pathway in Arabidopsis, but is targeted to mitochondria when expressed in yeast.
Journal J Exp Bot
Abstract AtTSPO is a TspO/MBR domain-protein potentially involved in multiple stress regulation in Arabidopsis. As in most angiosperms, AtTSPO is encoded by a single, intronless gene. Expression of AtTSPO is tightly regulated both at the transcriptional and post-translational levels. It has been shown previously that overexpression of AtTSPO in plant cell can be detrimental, and the protein was detected in the endoplasmic reticulum (ER) and Golgi stacks, contrasting with previous findings and suggesting a mitochondrial subcellular localization for this protein. To ascertain these findings, immunocytochemistry and ABA induction were used to demonstrate that, in plant cells, physiological levels of AtTSPO colocalized with AtArf1, a mainly Golgi-localized protein in plant cells. In addition, fluorescent protein-tagged AtTSPO was targeted to the secretory pathway and did not colocalize with MitoTracker-labelled mitochondria. These results suggest that the polytopic membrane protein AtTSPO is cotranslationally targeted to the ER in plant cells and accumulates in the Trans-Golgi Network. Heterologous expression of AtTSPO in Saccharomyces cerevisiae, yeast devoid of TSPO-related protein, resulted in growth defects. However, subcellular fractionation and immunoprecipitation experiments showed that AtTSPO was targeted to mitochondria where it colocalized and interacted with the outer mitochondrial membrane porin VDAC1p, reminiscent of the subcellular localization and activity of mammalian translocator protein 18 kDa TSPO. The evolutionarily divergent AtTSPO appears therefore to be switching its sorting mode in a species-dependent manner, an uncommon peculiarity for a polytopic membrane protein in eukaryotic cells. These results are discussed in relation to the recognition and organelle targeting mechanisms of polytopic membrane proteins in eukaryotic cells.
Volume 62(2)
Pages 497-508
Published 2011-1-1
DOI 10.1093/jxb/erq283
PII erq283
PMID 20847098
PMC PMC3003801
MeSH Arabidopsis / genetics Arabidopsis / metabolism* Arabidopsis Proteins / genetics Arabidopsis Proteins / metabolism* Endoplasmic Reticulum / genetics Endoplasmic Reticulum / metabolism Gene Expression* Membrane Proteins / genetics Membrane Proteins / metabolism* Mitochondria / genetics Mitochondria / metabolism* Protein Transport Saccharomyces cerevisiae / genetics* Saccharomyces cerevisiae / metabolism Secretory Pathway* trans-Golgi Network / genetics trans-Golgi Network / metabolism
IF 5.908
Times Cited 13
Arabidopsis / Cultured plant cells, genes pda06617 pda02760