Role of Glutamine Metabolism During Osteoblast Differentiation and Bone Formation

PROJECT SUMMARY Glutamine is a conditionally essential amino acid that has myriad uses in the cell. Aside from direct incorporation into protein, glutamine can be metabolized to generate nucleotides, other amino acids, the Krebs cycle intermediate α-ketoglutarate (αKG) which is important for energy production and anabolic reactions, and glutathione (GSH) to protect against oxidative stress. We recently determined that αKG and GSH are particularly important glutamine derived metabolites that are required at distinct stages of osteoblast differentiation. For example, our data indicates that αKG is required early in skeletal stem and progenitor cells to regulate proliferation and osteoblast specification. GSH is required later in specified pre-osteoblasts to govern osteoblast differentiation by neutralizing reactive oxygen species (ROS). Mechanistically, how αKG and ROS regulate proliferation, specification and differentiation remains enigmatic. Moreover, the enzymes that generate αKG from glutamine in osteoblasts have not been described. In this proposal, we will 1) establish the necessity of glutamate oxaloacetate transaminase 2 (GOT2) dependent αKG synthesis to regulate osteoblast differentiation and bone formation, 2) define the contribution of αKG to osteoblast energetics and intermediate metabolism, 3) elucidate the molecular regulation of osteoblast differentiation by ROS, and 4) evaluate the efficacy of antioxidants to rescue bone formation in a mouse model of human cleidocranial dysplasia. Our findings will have broad implications in bone development, maintenance of bone mass, skeletal repair and regeneration.