TY - JOUR
T1 - Regulation of human neuronal calcium channels by G protein βγ subunits expressed in human embryonic kidney 293 cells
AU - Shekter, Lee R.
AU - Taussig, Ronald
AU - Gillard, Samantha E.
AU - Miller, Richard J.
PY - 1997/8
Y1 - 1997/8
N2 - We examined the ability of different G protein subunits to inhibit the activity of human α1B and α1E Ca2+ channels stably expressed in human embryonic kidney (HEK) 293 cells together with β1B and α2Bδ Ca2+ channel subunits. Under normal conditions, Ca2+ currents in αlB-expressing cells showed little facilitation after a depolarizing prepulse. However, when we overexpressed the β2γ2 subunits of heterotrimeric G proteins, the time course of activation of the Ca2+ currents was considerably slowed and a depolarizing prepulse produced a large facilitation of the current as well as an acceleration in its time course of activation. Similar effects were not observed when cells were transfected with constitutively active mutants of the G protein α subunits αs, αi1, and αo or with the G protein β2 and γ2 subunits alone. Studies carried out in cells expressing α1E currents showed that overexpression of β2γ2 subunits produced prepulse facilitation, although this was of lesser magnitude than that observed with Ca2+ currents in α1B-expressing cells. The subunits β2 and γ2 alone produced no effects, nor did constitutively active αs, αi1, and αo subunits. Phorbol esters enhanced α1E Ca2+ currents but had no effect on α1B currents, suggesting that protein kinase C activation was not responsible for the observed effects. When α1E Ca2+ currents were expressed without their β subunits, they exhibited prepulse facilitation. These results demonstrate that α1E Ca2+ currents are less susceptible to direct modulation by G proteins than α1B currents and illustrate the antagonistic interactions between Ca2+ channel β subunits and G proteins.
AB - We examined the ability of different G protein subunits to inhibit the activity of human α1B and α1E Ca2+ channels stably expressed in human embryonic kidney (HEK) 293 cells together with β1B and α2Bδ Ca2+ channel subunits. Under normal conditions, Ca2+ currents in αlB-expressing cells showed little facilitation after a depolarizing prepulse. However, when we overexpressed the β2γ2 subunits of heterotrimeric G proteins, the time course of activation of the Ca2+ currents was considerably slowed and a depolarizing prepulse produced a large facilitation of the current as well as an acceleration in its time course of activation. Similar effects were not observed when cells were transfected with constitutively active mutants of the G protein α subunits αs, αi1, and αo or with the G protein β2 and γ2 subunits alone. Studies carried out in cells expressing α1E currents showed that overexpression of β2γ2 subunits produced prepulse facilitation, although this was of lesser magnitude than that observed with Ca2+ currents in α1B-expressing cells. The subunits β2 and γ2 alone produced no effects, nor did constitutively active αs, αi1, and αo subunits. Phorbol esters enhanced α1E Ca2+ currents but had no effect on α1B currents, suggesting that protein kinase C activation was not responsible for the observed effects. When α1E Ca2+ currents were expressed without their β subunits, they exhibited prepulse facilitation. These results demonstrate that α1E Ca2+ currents are less susceptible to direct modulation by G proteins than α1B currents and illustrate the antagonistic interactions between Ca2+ channel β subunits and G proteins.
UR - http://www.scopus.com/inward/record.url?scp=0030751811&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0030751811&partnerID=8YFLogxK
U2 - 10.1124/mol.52.2.282
DO - 10.1124/mol.52.2.282
M3 - Article
C2 - 9271351
AN - SCOPUS:0030751811
SN - 0026-895X
VL - 52
SP - 282
EP - 291
JO - Molecular Pharmacology
JF - Molecular Pharmacology
IS - 2
ER -