Biology subjects

Suttapitugsakul, S.

Publications and source records attributed to Suttapitugsakul, S..

3 recordsLinked to original sources

bioRxiv2024

O-GalNAc glycans enrich in white matter tracts and regulate nodes of Ranvier

Protein O-glycosylation is a critical modification in the brain, as genetic variants in the pathway are associated with both common and severe neuropsychiatric phenotypes. However, little is known about the most abundant type of O-glycan in the mammalian brain, which are O-GalNAc linked. Here, we determined the spatial localization, protein carriers, and cellular function of O-GalNAc glycans in mouse brain. We observed striking spatial enrichment of O-GalNAc glycans in white matter tracts and at nodes of Ranvier. Glycoproteomic analysis revealed that more than half of the identified O-GalNAc glycans were present on chondroitin sulfate proteoglycans termed lecticans, and display both domain enrichment and site-specific heterogeneity. Though genetic ablation in a single cell type failed to replicate the severe phenotypes seen in congenital disorders, inhibition of O-GalNAc synthesis in neurons reduced binding of Siglec-4, a known regulator neurite growth, and shortened the length of nodes of Ranvier. This work highlights a new function of O-GalNAc glycans in the brain and will inform future studies on their role in development and disease.

neuroscience↗

bioRxiv2019

Cutting in-line with iron: ribosomal function and non-oxidative RNA cleavage

Divalent metal cations are essential to the structure and function of the ribosome. Previous characterizations of the ribosome performed under standard laboratory conditions have implicated Mg2+ as a primary mediator of ribosomal structure and function. Possible contributions of Fe2+ as a ribosomal cofactor have been largely overlooked, despite the ribosomes early evolution in a high Fe2+ environment, and its continued use by obligate anaerobes inhabiting high Fe2+ niches. Here we show that (i) Fe2+ cleaves RNA by in-line cleavage, a non-oxidative mechanism that has not previously been shown experimentally for this metal, (ii) the first-order rate constant with respect to divalent cations is more than 200 times greater with Fe2+ than with Mg2+, (iii) functional ribosomes are associated with Fe2+ after purification from cells grown under low O2 and high Fe2+, and (iv) a small fraction of Fe2+ that is associated with the ribosome is not exchangeable with surrounding divalent cations, presumably because it is tightly coordinated by rRNA and buried in the ribosome. In total, these results expand the ancient role of iron in biochemistry and highlight a possible new mechanism of iron toxicity. Key PointsO_LIFe2+ cleaves rRNA by a non-oxidative in-line cleavage mechanism that is more than 200 times faster than in-line cleavage with Mg2+; C_LIO_LIribosomes purified from cells grown under low O2 and high Fe2+ retain ~10 Fe2+ ions per ribosome and produce as much protein as low O2, high Mg2+-grown ribosomes; C_LIO_LIa small fraction (~2%) of Fe2+ that is associated with the ribosome is not exchangeable. C_LI

molecular biology↗

bioRxiv2018

Dynamic G-quadruplexes on the surface of the human ribosome

Profound similarities and critical differences mark ribosomes across phylogeny. The ribosomal core, approximated by the prokaryotic ribosome, is universal, yet mammalian ribosomes are nearly twice as large as those of prokaryotes. Differences in size are due in part to rRNA expansion segments. Here we show rRNA tentacles of Expansion Segment 7 (ES7) of Homo sapiens can form G-quadruplexes in vitro. G-quadruplex-forming regions are located on the most surface-exposed regions of the ribosome, near the termini of rRNA tentacles. We characterized rRNA of the large ribosomal subunit by computation, circular dichroism, gel mobility, fluorescent probes, nuclease accessibility, electrophoretic mobility shifts and blotting. We investigated ES7 and oligomers derived from ES7, intact 28S rRNA, and 80S ribosomes and polysomes. We used mass spectrometry to identify proteins that bind to rRNA G-quadruplexes in cell lysates. Proteins that associate with rRNA G-quadruplexes include helicases (DDX3, CNBP, DDX21, DDX17) and heterogeneous nuclear ribonucleoproteins (hnRNPs). And finally, by multiple sequence alignments, we observed that G-quadruplex-forming sequences appear to be a general feature LSU rRNA of the phylum Chordata but not in other phyla. It is known that G-quadruplexes form in telomeres, promoters, and untranslated regions of mRNA but, to our knowledge, they have not been reported previously in ribosomes.

biochemistry↗