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Ca2+ current enhancement by alpha 2/delta and beta subunits in Xenopus oocytes: contribution of changes in channel gating and alpha 1 protein level.
Author(s) -
Shistik E,
Ivanina T,
Puri T,
Hosey M,
Dascal N
Publication year - 1995
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1995.sp021029
Subject(s) - beta (programming language) , alpha (finance) , xenopus , gating , membrane potential , g alpha subunit , biophysics , electrophysiology , protein subunit , chemistry , physics , microbiology and biotechnology , biology , biochemistry , medicine , neuroscience , gene , construct validity , nursing , computer science , patient satisfaction , programming language
1. A combined biochemical and electrophysiological approach was used to determine the mechanism by which the auxiliary subunits of Ca2+ channel enhance the macroscopic Ca2+ currents. Xenopus oocytes were injected with RNA of the main pore‐forming subunit (cardiac: alpha 1C), and various combinations of RNAs of the auxiliary subunits (alpha 2/delta and beta 2A). 2. The single channel open probability (Po; measured at 0 mV) was increased approximately 3‐, approximately 8‐ and approximately 35‐fold by alpha 2/delta, beta 2A and alpha 2/delta+beta 2A, respectively. The whole‐cell Ca2+ channel current was increased approximately 8‐ to 10‐fold by either alpha 2/delta or beta 2A, and synergistically > 100‐fold by alpha 2/delta+beta 2A. The amount of 35S‐labelled alpha 1 protein in the plasma membrane was not changed by coexpression of beta 2A, but was tripled by coexpression of alpha 2/delta (either with or without beta). 3. We conclude that the increase in macroscopic current by alpha 2/delta is equally due to changes in amount of alpha 1 in the plasma membrane and an increase in Po, whereas all of the effect of beta 2A is due to an increase in Po. The synergy between alpha 2/delta and beta in increasing the macroscopic current is due mainly to synergistic changes in channel gating.