C-Mannosylation: Previous Studies and Future Research Perspectives

C-linked glycosylation, one of the protein glycosylations, is a unique type of glycosylation in which an α-mannose is attached to the indole C2 carbon of a tryptophan residue via a C–C linkage and is so named C-mannosylation. C-mannosylation is enzymatically catalyzed in the endoplasmic reticulum (ER) lumen, and the N-terminal side Trp residue of the consensus amino acid sequence Trp-Xaa-Xaa-Trp/Cys (Xaa represents any amino acid) is often C-mannosylated. It has been reported that about 30 proteins are C-mannosylated, and the functions of C-mannosylation are becoming clear. In 2013, C. elegans dumpy-19 (dpy-19) was identified as a C-mannosyltransferase, and we revealed that DPY19L3, one of the human homologs of dpy-19, has similar activity in 2016. In this review, we describe previous studies about C-mannosylation, including our results and future research perspectives.