Determining the Role of Heme Metabolism in Muscle Function

Heme is an essential component for oxygen dependent life. I am fascinated by the diverse needs for heme and heme-proteins for different cellular mechanisms. My research program is focused on understanding how heme-associated mechanisms are coordinated. Cells either make heme or extract it from the environment. Heme is a substrate, ligand, and essential iron store. Heme is essential to cellular respiration and the formation of cytochromes, globins and nuclear hormone receptors. Heme-proteins are important for many cell functions including metabolism, and communication inside and between cells (from hormones to gases). Heme is clearly an important molecule. Yet, we still do not fully grasp how heme synthesis, storage, degradation or transport is balanced with the biological demands of cells, especially the unique demands in muscle cells (myocytes). The purpose of my research is to understand how heme metabolism is coordinated with the complex biological needs of myocytes. The synthesis of heme is dependent on the mitochondria, specialized organelles where oxygen is used to make energy. Mitochondria are variable in size, shape, content and turnover in different cells and organisms. In myocytes, balancing mitochondrial respiration (for energy) with calcium regulation (for contraction) is very complex and essential for sustaining life. Calcium release inside cells causes myocytes to contraction. Energy is consumed for calcium-induced contractions and calcium regulation is also energy dependent. Myocytes have an abundance of mitochondria and significant heme-protein requirements (myoglobin) to help transport oxygen to feed the mitochondria and supply energy. In myocytes, the mitochondria are uniquely co-localized with the endoplasmic reticulum, where calcium stores are regulated. These unique needs and proximity require the mitochondria and endoplasmic reticulum to work co-operatively to match calcium-contraction with the energy needed for contraction. My research program seeks to understand: 1) how mitochondrial function affects the production of heme, 2) how heme, or the need for heme, affects contractility and vice versa, 3) what the key mechanisms and proteins are that regulate a myocytes complex demands for heme, energy, and tightly regulated calcium stores. Using chemical and genetic methods, we will manipulate the amount of heme formed in myocytes under different biological states including: sympathetic drive, stretch and hypoxia. We will determine how heme synthesis impacts calcium stores in the mitochondria and endoplasmic reticulum. Then we will seek out the molecular mechanisms, such as DNA binding transcription factors that regulate heme homeostasis in myocytes. The research we will conduct will help train new HQP in many techniques like: cell culture, protein chemistry, muscle physiology and genetics. Students and technicians will learn many new techniques such as western blotting, gel and liquid chromatography, polymerase chain reaction, flow cytometry, whole muscle function analysis, calcium measurements and intracellular organelle labeling. These studies will be important for understanding how heme metabolism and biological demands are coordinated. These findings would provide important new information for textbooks and have a significant impact in our understanding basic cell functions.