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  • Isotretinoin We report here a patient with

    2021-09-16

    We report here a patient with a one-base frame-shift deletion in the PURA gene that presented an unusual phenotype including persistent hypoglycorrhachia. We propose a possible link between hypoglycorrhachia and PURA dysfunction postulating PURA as a GLUT1 regulator. We therefore hypothesize that mutations in PURA can decrease GLUT1 expression and in consequence provoke a GLUT1 deficiency-like phenotype.
    Materials and methods
    Results
    Discussion We have presented a patient with a monoallelic defect in the PURA gene that causes the expression of a truncated dysfunctional protein, explaining the phenotype. This patient's clinical setting with marked hypoglycorrhachia and hypertrophic myocardiopathy expands PURA deficiency's phenotype since this has not been previously reported in patients [1], [2], [6] nor in PURA deficient mice models [4], [5]. We did not deepen our research in the cardiomyopathy, but PURA as a transcription regulator of genes such as alpha Isotretinoin [27] and alpha myosin [16] in cardiomyocytes, could be responsible to cause cardiac abnormalities when dysfunctional. We did extend our observations regarding the hypoglycorrhachia and were able to prove a GLUT1 downregulation in the patient's peripheral blood cells. It is reasonable to infer that this decrease of GLUT1 could also be happening in the blood-brain barrier and in this manner explain the detected hypoglycorrhachia. Since mutations in the SLC2A1 gene were discarded, and based on the fact that PURA is known to be a transcriptional/translational regulator, we propose that PURA could be a facilitator of the expression of GLUT1. Therefore, mutations affecting its function would reduce the amount of GLUT1. These findings propose an expansion of the phenotype associated to PURA mutations and presents GLUT1 as a yet unknown PURA target. PURA binds to purine rich single and double-stranded nucleic acids in a sequence specific manner. (GGN)n [28], (CGG)n [14], (CAG)n [29], (G4C2)n [30], [31] repeats and the CCCGGCC [32] sequence are all known PURA binding sites [30]. It binds to Guanines and additionally contacts with the phosphodiester backbone. Apart from its ability to bind RNA and ssDNA, PURA has a dsDNA-destabilizing activity in an ATP-independent fashion [33], [34], important for DNA replication and transcription regulation. As a transcription activator, PURA contacts the purine-rich strand of promoter regions and displaces the pyrimidine-rich strand, allowing the binding of other proteins, transcription factors and therefore transcription activation [34]. PURA also has a role in protein translation binding to non-coding RNAs and mRNAs, as in compartmentalized translation in neurons [15]. Based on PURA's known functions, GLUT1´s regulation could be associated to PURA-dependent transcription activation or translation regulation. The specific PURA-binding sequences mentioned above are all present in the SLC2A1 promoter regions and/or the SLC2A1 mRNA, making GLUT1 a possible PURA target. We consider that hypoglycorrhachia could be added to the PURA syndrome clinical spectrum, and so PURA should be tested in a hypoglycorrhachia setting after GLUT1 mutations are ruled out. The ketogenic diet, known treatment for GLUT1 deficiency [35], did not show any benefit in our patient. This could be due to the many possible PURA targets that are dysregulated in PURA deficiency, making GLUT1 not the only one. Anyhow, ketogenic diet might be useful in some PURA patients when seizures don't respond to antiepileptic drugs, as in other refractory epilepsy settings [36].
    Conflict of interest
    Funding
    Acknowledgements
    Introduction Autophagy, a catabolic process involved in the degradation of cellular constituents and organelles, sustains core metabolic functions and nutritional requirements during starvation or stress. Autophagy also supports the anabolic demands of rapidly proliferating tumor cells; for example, in cancers driven by oncogenic Ras activation, genetic autophagy inhibition leads to multiple defects in mitochondrial metabolism, including decreased production of tricarboxylic acid (TCA) cycle intermediates and reduced oxidative phosphorylation (Guo et al., 2011, Yang et al., 2011). In addition to supporting mitochondrial metabolism, autophagy has been demonstrated to promote glycolysis during oncogenic transformation. Genetic deletion of multiple core autophagy regulators, including ATG3, ATG5, ATG7, and FIP200, impairs oncogenic Ras-driven glycolysis in mouse fibroblasts (Lock et al., 2011, Wei and Guan, 2012). Similar results are observed in human triple-negative breast cancer cells and in a transgenic model of polyoma middle T (PyMT) mammary cancer (Lock et al., 2011, Wei et al., 2011). Moreover, ATG7 knockdown in chronic myeloid leukemia cells impairs glucose uptake and glycolysis, sensitizing cells to tyrosine kinase inhibitor-induced cell death (Karvela et al., 2016). Nevertheless, the precise mechanisms through which the autophagy pathway facilitates glycolysis remain unclear. Here, we uncover that the core autophagy machinery promotes glycolytic metabolism by augmenting intracellular glucose uptake into both normal and oncogenic cells.