Lindahl Lab

All eukaryotic cells, from yeast to humans, require transition metals such as iron, copper, manganese, and zinc. In fact, metals bind to nearly half of all proteins in cells. Transition metals have unique catalytic properties that make them essential for cellular survival. Ironically, these same properties also make them dangerous to cells; thus, the “trafficking” of metals within cells must be tightly regulated. Dysregulation of metal ion trafficking is associated with certain diseases, often involving oxidative damage and perhaps aging. Our lab is interested in the cell biology of such metal ions. Our primary focus is iron, but we are also interested in copper (and currently nickel) trafficking. Most of our studies involve budding yeast, Saccharomyces cerevisiae, as it is the “workhorse” of eukaryotic cells in which molecular-level mechanisms can be most readily probed. However, we also study or have recently studied bacteria (mainly Escherichia coli), archaea (Pyrococcus furiosus), human Jurkat cells, as well as blood and tissues from various genetic strains of mice – and even pigs.

Rather than focus on a single iron-containing protein, we take a “systems’ level” approach to understanding iron trafficking. Iron is at the active site of nearly 100 proteins in a yeast cell. Iron plays important roles in cellular energetics, metabolism, and DNA replication and repair. When iron enters a cell, it is trafficked through the cytosol to various organelles, such as mitochondria, nuclei, vacuoles, endoplasmic reticula, and the Golgi. How can we hope to understand such a complicated process as a unified system?

Mössbauer Spectroscopy of whole cells and organelles

We use many standard biochemical and molecular-biological methods for studying these processes, but Mössbauer spectroscopy stands out because it is the most powerful spectroscopic probe of iron. Like NMR, Mössbauer measures the energies of nuclear transitions involving 57Fe (I = ½); it can distinguish different oxidation states and spin states of iron, as well as identify various types of iron-sulfur clusters, heme centers, and nonheme iron centers. There are very few Mössbauer spectrometers world-wide, and we have 4 instruments in the lab. Using Mössbauer we analyze various genetic strains of yeast, grown under various conditions. We compare the iron content of such cells to that of wild-type cells. Typically, we isolate organelles and identify their iron contents. We have previously isolated cytosol, mitochondria, and vacuoles, and are currently focused on nuclei and endoplasmic reticula. We aim to assemble the “pieces of the puzzle” to characterize the entire iron-ome of the cell. No one does this.

Copper Trafficking

Although most of our studies involve iron, we are also probing the means by which copper is trafficked from the site at which it enters the cell to the mitochondria where it is installed in Respiratory Complex IV, cytochrome c oxidase. We are attempting to solve this 50-year-old puzzle using our LC-ICP-MS system in conjunction with ESI-MS, selected genetic strains of yeast, and various copper isotopes. We have identified a copper-containing species that is found in both cytosol and mitochondria and are probing whether it might be the sought-after trafficking species. We have also detected some low-intensity low-molecular-mass copper species in the cytosol that have not been observed previously and are investigating whether they may be involved in inter-organelle trafficking.