[2015 Spring Life Sciences & IBB Regular Seminar]
          
            
        ▶Subject: Lysosome related compartments in trace metal homeostasis
          
        ▶Speaker: Prof. Sabeeha S Merchant   (University of California, Los Angeles)
                  
        ▶Date: 4:00PM/May/29(Fri.)/2015
           
        ▶Place: Auditorium(1F), Postech Biotech Center
          
                *Abctract
               Trace elements like Cu, Fe and Zn are critical for life because they enable chemistries that are not readily possible with the functional groups found on proteins and nucleic acids. Their reactivity, which makes them useful in biology, also gives them the potential to be toxic intracellular if the chemistry is not controlled. Accordingly, there are mechanisms in every organism to regulate the uptake, distribution and storage of these elements. We have developed Chlamydomonas, a green alga in the green plant lineage, as a reference organism for understanding trace metal homeostasis, especially in the context of the biogenesis and maintenance of the bioenergetics membranes of respiration and photosynthesis. Each organism has an elemental quota based on the metabolic requirement for these elements in cellular constituents. However, we can disrupt the metal quota either genetically or by physiological manipulation of Chlamydomonas cells. For instance, during Zn limitation, Chlamydomonas hyperaccumulates Cu, dependent on the nutritional Cu sensor Crr1, but is functionally Cu-deficient. In this situation, the metal is in chemical excess but biologically invisible because it accumulates in an intracellular compartment. We have used fluorescence probes for Cu(I) as well as nano-secondary ion mass spectrometry to visualize these structures, which based on staining for pH and polyphosphate, appear to be lysosome-related compartments. X-ray absorption spectroscopy (XAS) is consistent with Cu(I) accumulation in an ordered structure. Cu isotope labeling demonstrates that cuprosome-sequestered Cu(I) becomes bioavailable with priority over extracellular Cu when homeostasis is restored, indicative of the cuprosome being a dynamic metal-storing structure in the cell. When Fe is over-supplied to cells, Fe will hyper-accumulate in this compartment rather than in chloroplast ferritin. Instead ferritin appears to hold Fe only while it is en route to the compartment. We have used isotope labelling studies in wild-type and compartment-deficient vtc mutants to establish the role of chloroplast ferritin in iron homeostasis

        ▶Inquiry: Prof. Lee, Youngsook(279-2296)
                
          
          * This seminar will be given in English.
      please refrain from taking photos during seminars. *