Résumé
Voltage-gated calcium channels can be classified into high voltage activated (HVA) and low voltage activated (LVA or T-type) subtypes. The molecular diversity of HVA channels primarily results from different genes encoding their pore-forming
α
1 subunits. These channels share a common structure with an
α
1 subunit associated with at least two regulatory subunits (
β,
α
2–
δ). Any of the six
α
1-related channels identified to date are regulated in their functional properties through an interaction with the ancillary
β-subunit. By contrast, the diversity and the molecular identity of LVA or T-type calcium channels have yet to be defined. Whether LVA channels are modulated by a
β-subunit, like HVA channels, is unknown. To address this issue, we have used an antisense strategy to inhibit
β-subunit expression in the NG 108-15 neuroblastoma cell line. Differentiated NG 108-15 cells express both LVA and HVA channels. We found that LVA currents were unaffected when cells were incubated with
β-antisense, while HVA currents were drastically decreased. Since LVA Ca channel currents in NG 108-15 cells are not regulated by
β-subunits, it is reasonable to postulate that the pore-forming subunit(s) of these channels lacks an interaction domain with a
β-subunit (AID). This molecular feature, which is common to various T-type channels, indicates further that LVA calcium channels belong to a channel family structurally distant from HVA channels.