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ARS Home » Midwest Area » Urbana, Illinois » Global Change and Photosynthesis Research » Research » Publications at this Location » Publication #208051

Title: Sucrose synthase interaction with voltage-dependent anion channel suggests a potential role for the enzyme in inter-organellar signaling

item Huber, Steven
item Sachs, Martin

Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 1/2/2007
Publication Date: 7/1/2007
Citation: Chalivendra, S., Huber, S.C., Sachs, M.M., Rhoads, D. 2007. Sucrose synthase interaction with voltage-dependent anion channel suggests a potential role for the enzyme in inter-organellar signaling [abstract]. American Society of Plant Biologists Annual Meeting. 824.7

Interpretive Summary:

Technical Abstract: Sucrose synthase (SUS) is a key enzyme in plant sucrose catabolism and uniquely able to mobilize sucrose into multiple pathways involved in metabolic, structural, and storage functions. SUS is encoded by three genes in maize: sh1, sus1 and sus2 and the active enzyme is a homo or hetero-tetramer. Our recent work indicates that the biological function of SUS extends beyond its biochemical activity (Subbaiah et al., 2006). This inference is based on the following observations: a) tissue-specific, isoform-dependent and metabolically-regulated association of SUS with mitochondria and b) isoform-specific and anoxia-responsive interaction of SUS with the voltage-dependent anion channel (VDAC), the major outer mitochondrial membrane protein. Here we show that both VDAC and SUS are also localized to the nucleus in maize seedling tissues and present evidence for their inverse regulation in these two cellular compartments under oxygen-deprivation stress. SUS localizes to nuclei in a tissue- & isoform-specific, phosphorylation-dependent and anoxia-enhanced manner. Unlike in mitochondria where the protein is predominantly a monomer, SUS occurs mostly as an oligomer in the nuclei, as indicated by glycerol velocity gradient analysis. Further, VDAC exists in a dynamic equilibrium of mono-& oligomers in mitochondria as well as nuclei and is de-oligomerized under anoxia, indicating that oligomerization may be needed for its normal function (under aerobic conditions). VDAC also forms supramolecular complexes both in mitochondria and nuclei. Co-immunoprecipitation and immuno-affinity chromatography analysis indicate that the composition of these complexes is altered under anoxia. The de-oligomerization of VDAC induced under prolonged anoxia seems to cause a movement of VDAC and SUS out of mitochondria into the nucleus. This shuttling of the proteins to nuclei temporally coincides with the initiation of cell death in anoxic maize tissues. We propose that the inter-compartmental movement of SUS and VDAC may report the energy crisis to the nuclei and signal the activation of the cell death pathway