Asparagine-linked glycosylation modifies voltage-dependent gating properties of Ca_V3.1-T-type Ca²⁺ channel

T-type channels are low-voltage-activated channels that play a role in the cardiovascular system particularly for pacemaker activity. Glycosylation is one of the most prevalent post-translational modifications in protein. Among various glycosylation types, the most common one is asparagine-linked (N-linked) glycosylation. The aim of this study was to elucidate the roles of N-linked glycosylation for the gating properties of the Ca_V3.1-T-type Ca²⁺ channel. N-linked glycosylation synthesis inhibitor tunicamycin causes a reduction of Ca_V3.1-T-type Ca²⁺ channel current (Ca_V3.1-I_Ca.T) when applied for 12 h or longer. Tunicamycin (24 h) significantly shifted the activation curve to the depolarization potentials, whereas the steady-state inactivation curve was unaffected. Use-dependent inactivation of Ca_V3.1-I_Ca.T was accelerated, and recovery from inactivation was prolonged by tunicamycin (24 h). Ca_V3.1-I_Ca.T was insensitive to a glycosidase PNGase F when the channels were expressed on the plasma membrane. These findings suggest that N-glycosylation contributes not only to the cell surface expression of the Ca_V3.1-T-type Ca²⁺ channel but to the regulation of the gating properties of the channel when the channel proteins were processed during the folding and trafficking steps in the cell.