A group from Translational Research Unit, Chulabhorn Research Institute, Bangkok, Thailand, etc. has reported about O-glycosylation of PD-1.
https://www.nature.com/articles/s41598-023-36203-3#Abs1
It was found that the stalk region of PD-1 at T153, S157, S159, and T168 are modified by sialylated O-glycan with core 1–and core 2–based structures.
The most likely function of these modifications would forming a rod-like structure and stretching the receptor on the cell surface with the steric interaction between O-glycans and the peptide backbone in the stalk region.
