TBONE and phosphonates in mineralization during aging

Washington University, Saint Louis MO

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Abstract

Mineralization is a process through which an organic substance becomes impregnated by inorganic substances. It is critically important to biology and when disrupted or hyperactivated contributes to wide-ranging effects on human health particularly in aging populations. For example, deficiencies in mineralization contribute to osteoporosis and cancer progression in bone, whereas elevated mineralization contributes to vascular disease such as atherosclerosis and kidney disease. The mechanism of action of the most commonly used drug class for treating several of these conditions, Nitrogenous Bisphosphonates (NBPs), is poorly understood. Through genetic screening in human cells we identified several genes whose loss of function led to resistance to the cytotoxic effects of the NBP, Alendronate (Fosamax®). We named these genes, Targets of BisphOsphonate NitrogEnous (heretofore TBONE1, TBONE2?). We show that TBONE1 is required both for biochemical responses triggered by NBPs as well as for bone function. Endogenous nitrogenous phosphonates (NPs), which are chemically related to NBPs and come from our diet and microbiome, potently regulate mineralization in bone-synthesizing osteoblasts in a TBONE1-dependent manner. Lastly, TBONE1 deficient mice have low body mass, deregulated markers of bone remodeling and reduced lifespan. These findings suggest that phosphonates acting through TBONE1 are critical for tissue mineralization. In this proposal, we will test TBONE genes with the following aims: 1) Dissection of the mechanisms of TBONE molecular interactions; 2) Elucidation of the TBONE1-phosphonate pathway in the bones and vasculature of mice. The identification of novel TBONE genes suggests an unexpected new understanding of and path of investigation for some of the most widely used medications, bisphosphonates. Additionally, that naturally occurring phosphonates stimulate mineralization suggests an important new determinant and safer therapeutic approach for numerous aging-associated conditions.