Surface expression and function of Ca3.2 T-type calcium channels are controlled by asparagine-linked glycosylation

Low-voltage-activated T-type calcium channels play important roles in neuronal physiology where they control cellular excitability and synaptic transmission. Alteration in T-type channel expression has been linked to various pathophysiological conditions such as pain arising from diabetic neuropathy. In the present study, we looked at the role of asparagine (N)-linked glycosylation on human Ca3.2 T-type channel expression and function. Manipulation of N-glycans on cells expressing a recombinant Ca3.2 channel revealed that N-linked glycosylation is critical for proper functional expression of the channel. Using site-directed mutagenesis to disrupt the canonical N-linked glycosylation sites of Ca3.2 channel, we show that glycosylation at asparagine N192 is critical for channel expression at the surface, whereas glycosylation at asparagine N1466 controls channel activity. Moreover, we demonstrate that N-linked glycosylation of Ca3.2 not only controls surface expression and activity of the channel but also underlies glucose-dependent potentiation of T-type Ca current. Our data suggest that N-linked glycosylation of T-type channels may play an important role in aberrant upregulation of T-type channel activity in response to glucose elevations.