In situ investigation of mammalian inorganic polyphosphate localization using novel selective fluorescent probes JC-D7 and JC-D8.

Inorganic polyphosphate (polyP) is a polymer composed of many orthophosphates linked together by phosphoanhydride bonds. Recent studies demonstrate that in addition to its important role in the function of microorganisms, polyP plays multiple important roles in the pathological and physiological function of higher eukaryotes, including mammalians. However, due to the dramatically lower abundance of polyP in mammalian cells when comparing to microorganisms, its investigation poses an experimental challenge. Here, we present the identification of novel fluorescent probes that allow for specific labeling of synthetic polyP in vitro as well as endogenous polyP in living cells. These probes demonstrate high selectivity for the labeling of polyP that was not sensitive to a number of ubiquitous organic polyphosphates, notably RNA. Use of these probes allowed us to demonstrate the real time detection of polyP release from lysosomes in live cells. Furthermore, we have been able to detect the increased levels of polyP in cells with Parkinson's disease related mutations.