Summary- paper 55:
Dynamic movement of the Golgi unit and its glycosylation enzyme zones
Akihiro Harada, Masataka Kunii, Kazuo Kurokawa, Takuya Sumi, Satoshi Kanda, Yu Zhang, Satomi Nadanaka, Koichiro M. Hirosawa, Kazuaki Tokunaga, Takuro Tojima, Manabu Taniguchi, Kenta Moriwaki, Shin-ichiro Yoshimura, Miki Yamamoto-Hino, Satoshi Goto, Toyomasa Katagiri, Satoshi Kume, Mitsuko Hayashi-Nishino, Miyako Nakano, Eiji Miyoshi, Kenichi G. N. Suzuki, Hiroshi Kitagawa & Akihiko Nakano
Nature Communications, 2024
Questions/gaps addressed:
- The distribution of glycosylation enzymes in the Golgi apparatus has been well examined for cis-trans distribution but where do they localise within a single cisterna?
Key methods:
- CRISPR-Cas9 knock-in for endogenous tagging
- super-resolution confocal live imaging microscopy SCLIM, immunoelectron microscopy.
- Enzymes studied:
Early stage:
- N-glycosylation enzyme, MGAT1 (Alpha-1,3-Mannosyl-Glycoprotein 2-Beta-N-Acetylglucosaminyltransferase),
- O-glycosylation enzyme, GALNT6 (Polypeptide N-Acetylgalactosaminyltransferase 6)
- GAG synthesising enzyme, XYLT2 (Xylosyltransferase 2)
Late stage:
- β4GalT1 (beta4-galactosyl transferase 1), an enzyme synthesising polylactosamine on both N- and O-glycans
- NDST1 (N-Deacetylase And N-Sulfotransferase 1), which catalyses the transfer of sulphate to the nitrogen of glucosamine in a GAG molecule, heparan sulphate
- Golgi discs as the Golgi ‘units’: dispersed the Golgi by nocodazole, which dissociates the large Golgi apparatus into smaller Golgi discs, or ‘mini-stacks’ surrounded by giantin or other golgins (golgin-84 and TMF1).
- RUSH construct of syndecan2 (SDC2), a substrate protein for GAG modification to look at kinetic signature of colocalization with early and late glycoslation enzymes.
Major takeaways:
- Mainly observational. Glysocylation enzymes loaclize to specific ‘zones’. Treatment with or not with nocodazole does not change the observed zones. The glycosylation substrates enter the glycosylation zones according to the order of the glycosylation reaction.