A novel proteomic approach reveals a role for Mg‐protoporphyrin IX in response to oxidative stress

Abstract

The presence of genes encoding organellar proteins in different cellular compartments necessitates a tight coordination of expression by the different genomes of the eukaryotic cell. This coordination of gene expression is achieved by organelle-to-nucleus communication. Stress-induced perturbations of the tetrapyrrole pathway trigger large changes in nuclear gene expression. In order to investigate whether the tetrapyrrole Mg-ProtoIX itself is an important part of plastid-to-nucleus communication, we used an affinity column containing Mg-ProtoIX covalently linked to an Affi-Gel matrix. The proteins that bound to Mg-ProtoIX were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis combined with nano liquid chromatography-mass spectrometry (MS)/MS. Thus, we present a novel proteomic approach to address the mechanisms involved in cellular signaling and we identified interactions between Mg-ProtoIX and a large number of proteins associated with oxidative stress responses. Our approach revealed an interaction between Mg-ProtoIX and the heat shock protein 90-type protein, HSP81-2 suggesting that a regulatory complex including HSP90 proteins and tetrapyrroles controlling gene expression is evolutionarily conserved between yeast and plants. In addition, our list of putative Mg-ProtoIX-binding proteins demonstrated that binding of tetrapyrroles does not depend on a specific amino acid motif but possibly on a specific fold of the protein.

HSP90, ZTL, PRR5 and HY5 integrate circadian and plastid signaling pathways to regulate CBF and COR expression.

“…Oxidative stress results in reduced flux through the tetrapyrrole biosynthetic pathway and a significant accumulation of the chlorophyll intermediates Mg-ProtoIX and Mg-ProtoIX-ME (Stenbaek et al, 2008;Kindgren et al, 2011;Zhang et al, 2011). Reduced flux through the tetrapyrrole pathway and the accumulation of Mg-ProtoIX were shown to inhibit the ATPase activity of HSP90, which in turn resulted in reduced expression of PhANGs via HY5 (Kindgren et al, 2012).…”

“…As a result of this lesion, the crd mutant overaccumulates Mg-ProtoIX-ME and the upstream intermediate magnesium protoporphyrin IX (Mg-ProtoIX) that, in turn, triggers a plastid signal regulating nucleus-encoded genes (Tottey et al, 2003;Bang et al, 2008). In the wild type, MgProtoIX and Mg-ProtoIX-ME were shown to accumulate transiently when plants were exposed to oxidative stress (Stenbaek et al, 2008;Kindgren et al, 2011;Zhang et al, 2011), and in response to the tetrapyrrole accumulation, the ATPase activity of cytosolic HEAT SHOCK PROTEIN90 (HSP90) proteins is inhibited, which leads to a change in nuclear gene expression (Kindgren et al, 2012). HSP90 is a molecular chaperone that interacts with proteins in their near-native state and is essential for maintaining the activity of signaling proteins (Young et al, 2001) as well as preventing the protein aggregation of freshly translated chloroplast preproteins (Fellerer et al, 2011).…”

Increased expression of Fe-chelatase leads to increased metabolic flux into heme and confers protection against photodynamically induced oxidative stress

“…7,9). It has been suggested that the peroxidases APX1 and PER22 are involved in the degradation of Proto IX and MgProto IX (ME) into non-toxic compounds (Dayan et al 1999;Kindgren et al 2011). HO is associated with heme degradation and suggested as the antioxidant machinery of the cell through the role of its product biliverdin IXα in preventing oxidative cell damage in animal systems (Otterbein et al 2003).…”

Evidence for a SAL1-PAP Chloroplast Retrograde Pathway That Functions in Drought and High Light Signaling in Arabidopsis

“…Examples of biogenic control mutants include the snowy cotyledon (Albrecht et al, 2010) and genomes uncoupled (gun) mutants (Susek et al, 1993;Larkin et al, 2003;Strand et al, 2003;Koussevitzky et al, 2007;Ruckle et al, 2007). With respect to biogenic control, a tetrapyrrole was proposed to move from the chloroplast to cytosol where it was hypothesized it would interact with cytosolic targets such as HSP90 (Strand et al, 2003;Kindgren et al, 2011). However, this has been actively debated by other groups (Mochizuki et al, 2008;Moulin et al, 2008).…”