N-Glycosylation of the voltage-gated sodium channel ?2 subunit is required for efficient trafficking of NaV1.5/?2 to the plasma membrane.

ABSTRACT: The voltage-gated sodium channel is critical for cardiomyocyte function and consists of a protein complex comprising a pore-forming ? subunit and two associated ? subunits. It has been shown previously that the associated ?2 subunits promote cell surface expression of the ? subunit. The major ? isoform in the adult human heart is NaV1.5, and germline mutations in the NaV1.5-encoding gene, sodium voltage-gated channel ? subunit 5 (SCN5A), often cause inherited arrhythmias. Here, we investigated the mechanisms that regulate ?2 trafficking and how they may determine proper NaV1.5 cell surface localization. Using heterologous expression in polarized Madin-Darby canine kidney cells, we show that ?2 is N-glycosylated in vivo and in vitro at residues 42, 66, and 74, becoming sialylated only at Asn-42. We found that fully nonglycosylated ?2 was mostly retained in the endoplasmic reticulum, indicating that N-linked glycosylation is required for efficient ?2 trafficking to the apical plasma membrane. The nonglycosylated variant reached the cell surface by bypassing the Golgi compartment at a rate of only approximately one-third of that of WT ?2. YFP-tagged, nonglycosylated ?2 displayed mobility kinetics in the plane of the membrane similar to that of WT ?2. However, it was defective in promoting surface localization of NaV1.5. Interestingly, ?2 with a single intact glycosylation site was as effective as the WT in promoting NaV1.5 surface localization. In conclusion, our results indicate that N-linked glycosylation of ?2 is required for surface localization of NaV1.5, a property that is often defective in inherited cardiac arrhythmias.

SUBMITTER: Cortada E 

PROVIDER: S-EPMC6827310 | biostudies-literature | 2019 Nov

REPOSITORIES: biostudies-literature