M. Rousset et al., Functional roles of gamma(2), gamma(3) and gamma(4), three new Ca2+ channel subunits, in P/Q-type Ca2+ channel expressed in Xenopus oocytes, J PHYSL LON, 532(3), 2001, pp. 583-593
1. Stargazin or gamma (2), the product of the gene mutated, in the stargaze
r mouse, is a homologue of the gamma (1) protein, an accessory subunit of t
he skeletal muscle L-type Ca2+ channel. gamma (2) is selectively-expressed
in the brain, and considered to be a putative neuronal Ca2+ channel subunit
based mainly on homology to gamma (1). Two new members of the gamma family
expressed in the brain have recently been identified: gamma (3) and gamma
(4).
2. We have co-expressed, in Xenopus oocytes, the human gamma (2), gamma (3)
and gamma (4) subunits with the P/Q-type (Ca(V)2.1) Ca2+ channel and diffe
r ent regulatory subunits (alpha (2)-delta; beta (1), beta (2), beta (3) or
beta (4)).
3. Subcellular distribution of the gamma subunits confirmed their membrane
localization.
4. Ba2+ currents, recorded using two-electrode voltage clamp, showed that t
he effects of the gamma subunits on the electrophysiological properties of
the channel are, most of the time, minor. However, a fraction of the oocyte
s expressing beta subunits displayed an unusual slow-inactivating Ba2+ curr
ent. Expression of both beta and gamma subunits increased the appearance of
the slow-inactivating current.
5. Our data support a role for the gamma subunit as a brain Ca2+ channel mo
dulatory subunit and suggest that beta and gamma subunits are involved in a
switch between two regulatory modes of the P/Q-type channel inactivation.