Deglycosylation of Shaker KV channels affects voltage sensing and the open–closed transition

Abstract

Most membrane proteins are subject to posttranslational glycosylation, which influences protein function, folding, solubility, stability, and trafficking. This modification has been proposed to protect proteins from proteolysis and modify protein-protein interactions. Voltage-activated ion channels are heavily glycosylated, which can result in up to 30% of the mature molecular mass being contributed by glycans. Normally, the functional consequences of glycosylation are assessed by comparing the function of fully glycosylated proteins with those in which glycosylation sites have been mutated or by expressing proteins in model cells lacking glycosylation enzymes. Here, we study the functional consequences of deglycosylation by PNGase F within the same population of voltage-activated potassium (K) channels. We find that removal of sugar moieties has a small, but direct, influence on the voltage-sensing properties and final opening-closing transition of Shaker K channels. Yet, we observe that the interactions of various ligands with different domains of the protein are not affected by deglycosylation. These results imply that the sugar mass attached to the voltage sensor neither represents a cargo for the dynamics of this domain nor imposes obstacles to the access of interacting molecules.

Cell glycosaminoglycans content modulates human voltage‐gated proton channel (HV1) gating

“…The activity of these enzymes does not differ on both CHO cell lines [62]. N ‐ and O ‐glycosylation can modulate voltage‐gated Na + , K +, and Ca 2+ channels function and trafficking [39,85,86]. (b) Using NetOGlyc 4.0 [87], YinOYang 1.2 [88], and DictyOGlyc‐1.1 [89] servers we identified three putative O ‐glycosylation sites located in the N‐terminal domain (threonine 10 and 60, and serine 63) of the full‐length hH V 1.…”

Potassium Channels, Glucose Metabolism and Glycosylation in Cancer Cells

“…The same study also found that N-glycosylation of at least one (any) of the glycosylation sites is required for the expression of the Kv12.2 channel on the cell surface [171]. Similarly, the attachment of a sugar chain within the S1-S2 linker promotes the surface expression and stability of ion channels and directly affects their gating and voltage sensitivity [174]. Studies conducted on wild-type and mutant (lacking N-glycosylation sites) Kv3.1 channels suggest that glycosylation is essential for proper folding and expression of this channel on the cell surface and also affects the opening of the voltage-dependent gate of the Kv3.1 channel [175].…”