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- An endoribonuclease of the YicC-like family delays sporulation via sRNA degradation in Clostridioides difficilePublication . Martins, Diogo; Salgueiro, Bruno; Sobral, Daniel; Gragera, Marcos; Hensel, Zach; Henriques, Adriano O.; Romão, Célia V.; Serrano, MónicaClostridioides difficile CD25890 is a YicC-like endoribonuclease involved in regulating sporulation initiation, a process critical for the host-host transmission of this anaerobic pathogen. Using comparative transcriptomics we identified a small RNA, SQ528, that accumulates at higher levels in a CD25890 deletion mutant and we show that purified CD25890 cleaves SQ528 in a metal-dependent manner. Moreover, the overexpression of SQ528 increases sporulation under certain nutritional conditions phenocopying a CD25890 deletion mutant. CD25890 is an hexamer in solution and in vivo. An N-terminal domain, which self-interacts as assessed by size exclusion chromatography and a two hybrid assay, is essential for oligomerization of CD25890. A C-terminal domain harbours residues H230, E254, and E258, conserved among orthologues, important for catalysis. AlphaFold2 modelling and cryo-EM suggest an elongated barrel-like structure with an internal cavity lined with basic residues that may aid in RNA binding. We show that CD25890 forms a complex with polynucleotide phosphorylase which combines the endoribonuclease activity of the first with the exonucleolytic activity of the latter and leads to the complete degradation of SQ528. This study identifies a native substrate for the YicC-family of ribonucleases and advances our understanding of the role of CD25890 in sporulation initiation in C. difficile.
- LIMP-2 deficiency-associated glycolipid abnormalities in micePublication . da Silva Gaspar, Paulo Jorge Miranda; Marques, André R.A.; Ferraz, Maria J.; Damme, Markus; Krame, Gertjan; Mirzaian, Mina; Gijbels, Marion; Ottenhoff, Roelef; van Roomen, Cindy; Overkleeft, Herman S.; Schwake, Michael; Heybrock, Saskia; Macário, Maria Carmo; Saftig, Paul; Aerts, Johannes M.Glucocerebrosidase (GCase) catalyzes the lysosomal degradation of glucosylceramide (GlcCer). GCase deficiency results in Gaucher disease (GD), a lysosomal storage disorder with characteristic hepatosplenomegaly. Transport of GCase to lysosomes is mediated by the lysosomal integral membrane protein type 2 (LIMP-2). Deficiency of LIMP-2 leads to reduced cellular GCase levels and manifests as Action Myoclonic Renal Failure Syndrome (AMRF). We investigated the cause for the markedly different symptomatology of GD and AMRF. In tissues of Limp2 − /− mice no prominent abnormalities in lysosomal enzymes were noted except for variable deficiency of GCase, as measured with enzymatic activity assay and detection of active GCase molecules with an activity-based probe. Noteworthy, in LIMP-2-deficient mice, residual GCase is remarkably high in leukocytes. GCase deficiency in tissues does not correlate with increases in GlcCer, but rather with increases in glucosylsphingosine (GlcSph) and glucosylated cholesterol (GlcChol), both glucosylated metabolites derived from GlcCer. Isolated lysosomes from hepatocytes of Limp2 − /− mice revealed no prominent abnormalities in lysosomal matrix proteins except GCase. The Limp2 − /− tritosomes showed clear increases in GlcSph and GlcChol but not in GlcCer. In conclusion, our data imply a critical role of LIMP-2 in glycosphingolipid homeostasis. Despite low GCase levels striking GlcCer accumulation is avoided in tissues of LIMP-2 deficient mice.