Stable Isotopomers of <i>myo-</i>Inositol Uncover a Complex MINPP1-Dependent Inositol Phosphate Network
Minh Nguyen Trung, Stefanie Kieninger, Zeinab Fandi, Danye Qiu, Guizhen Liu, Neelay K. Mehendale, Adolfo Saiardi, Henning J. Jessen, Bettina G. Keller, Dorothea Fiedler
Abstract
-inositol and inositol phosphates. These probes were utilized in combination with nuclear magnetic resonance spectroscopy (NMR) and capillary electrophoresis mass spectrometry (CE-MS) to investigate InsP metabolism in human cells. The labeling strategy provided detailed structural information via NMR-down to individual enantiomers-which overcomes a crucial blind spot in the analysis of InsPs. We uncovered a novel branch of InsP dephosphorylation in human cells which is dependent on MINPP1, a phytase-like enzyme contributing to cellular homeostasis. Detailed characterization of MINPP1 activity in vitro and in cells showcased the unique reactivity of this phosphatase. Our results demonstrate that metabolic labeling with stable isotopomers in conjunction with NMR spectroscopy and CE-MS constitutes a powerful tool to annotate InsP networks in a variety of biological contexts.