Kollipara, L. | bioRxiv Science

bioRxiv2026

Isotopic tracing of scyllo-inositol uncovers its incorporation into phosphatidylinositols in mammalian cells

Inositols are a family of cyclic sugar alcohols comprising nine stereoisomers. Myo-inositol is the most abundant isomer found in humans and has been studied most extensively. It plays an important role in osmoregulation and is incorporated into membrane-anchored phosphatidylinositols. Scyllo-inositol is the second most abundant inositol isomer in the human brain and aberrant concentrations are associated with various diseases; however, its biological functions remain poorly understood. Here, the development and application of [13C6]scyllo-inositol as an isotopic tracer to study its metabolism is reported. A concise and robust synthetic route was established to obtain [13C6]scyllo-inositol from [13C6]myo-inositol in good yield. The uptake of [13C6]scyllo-inositol and responses of endogenous inositol isomers were measured in multiple cell lines by HILIC-MS/MS, showcasing the advantages of isotopic tracing. [13C6]scyllo-inositol proved to be a versatile isotopic tracer, when coupled with MS-based lipidomics and 2D NMR experiments. These experiments provide evidence that scyllo-inositol is incorporated into phosphatidylinositols in different cell lines. The results suggest a previously underappreciated role of scyllo-inositol in mammalian cells. The utilization of [13C6]scyllo-inositol will help to elucidate the role of scyllo-inositol metabolism in healthy and diseased states. SignificanceScyllo-inositol is a cyclic sugar alcohol found predominantly in the human brain. Changes in its concentration are associated with different diseases, and scyllo-inositol has been investigated as a potential drug against Alzheimers disease in clinical trials. However, its metabolic fate in mammalian cells is not well understood. We report here a synthetic strategy to obtain [13C6]scyllo-inositol and demonstrate, through isotopic tracing, its incorporation into phosphatidylinositols in different human-derived cell lines. This new stable isotopic tracer enables the investigation of the biological role of scyllo-inositol in mammals and beyond. HighlightsO_LIConcise synthesis of [13C6]scyllo-inositol C_LIO_LI[13C6]scyllo-inositol uptake and response of endogenous inositol isomers studied in multiple cell lines C_LIO_LIUse of [13C6]scyllo-inositol as an isotopic tracer in metabolomics and lipidomics experiments C_LIO_LIEvidence for scyllo-inositol incorporation into phosphatidylinositol in mammalian cells C_LI

biochemistry↗

bioRxiv2020

Coordination and assembly of protein complexes encoded across mitochondrial and nuclear genomes is assisted by CLPP2 in Arabidopsis thaliana

Protein homeostasis in eukaryotic organelles and their progenitor prokaryotes is regulated by a series of proteases including the caseinolytic protease (CLPP). CLPP has essential roles in chloroplast biogenesis and maintenance, but the significance of the plant mitochondrial CLPP remains unknown and factors that aid coordination of nuclear and mitochondrial encoded subunits for complex assembly in mitochondria await discovery. We generated knock-out lines of the single gene for the mitochondrial CLP protease subunit, CLPP2, in Arabidopsis thaliana. Mutants had higher abundance of transcripts from mitochondrial genes encoding OXPHOS protein complexes, while transcripts for nuclear genes encoding other subunits of the same complexes showed no change in abundance. In contrast, the protein abundance of specific nuclear-encoded subunits in OXPHOS complexes I and V increased in CLPP2 knockouts, without accumulation of mitochondrial-encoded counterparts in the same complex. Protein complexes mainly or entirely encoded in the nucleus were unaffected. Analysis of protein import, assembly and function of Complex I revealed that while function was retained, protein homeostasis was disrupted through decreased assembly, leading to accumulation of soluble subcomplexes of nuclear-encoded subunits. Therefore, CLPP2 contributes to the mitochondrial protein degradation network through supporting coordination and assembly of protein complexes encoded across mitochondrial and nuclear genomes. One sentence summaryCLPP contributes to the mitochondrial protein degradation network through supporting coordination and assembly of protein complexes encoded across mitochondrial and nuclear genomes.

plant biology↗