Neuronal T-Type Calcium Channels: Pharmacology and Investigation of Subunit Composition

摘要: Native Ca2+ channel currents in many cell types have been subdivided into two major categories depending upon their kinetics and voltage-dependent properties, high voltage-activated (HVA) low (LVA) or T-type (Carbone Lux 1984; Fedulova et al. 1985; Nilius 1985). HVA calcium channels are generated by hetero-oligomers consisting of (at least) a pore-forming al subunit auxiliary subunits termed α2-δ s. The cDNAs for nine cloned expressed: αlA, B, C, D, E, G, H, I S (Tanabe 1987; Ellis 1988; Dubel 1992; Perez-Reyes Schneider 1994; 1998)’, there four genes the s (Pragnell 1991; 1994). However, these subunits, any combination with different accessory only αlG αlH gives rise to current properties rapidly inactivating LVA current, although αlE also shows certain requisite characteristics (Bourinet 1996; Stephens 1997). In particular, alA, produce single external Ba2+ 12–25 pS 1996), rather than 5–7 pS, as reported systems (Huguenard, recently alG (Perez-Reyes 1998). Furthermore, more rapid inactivation (Huguenard 1996). expression Members this subfamily therefore likely underlie classical currents, slowly neuronal T may represent activation mixture αl including αlG, predicted previously (Chen Hess 1990).