Both N- and C-lobes of calmodulin are required for Ca2+-dependent regulations of CaV1.2 Ca2+ channels.
We investigated the concentration- and Ca(2+)-dependent effects of CaM mutants, CaM(12) and CaM(34), in which Ca(2+)-binding to its N- and C-lobes was eliminated, respectively, on the Ca(V)1.2 Ca(2+) channel by inside-out patch clamp in guinea-pig cardiomyocytes. Both CaM(12) and CaM(34) (0.7-10muM) applied with 3mM ATP produced channel activity after "rundown". Concentration-response curves were bell-shaped, similar to that for wild-type CaM. However, there was no obvious leftward shift of the curves by increasing [Ca(2+)], suggesting that both functional lobes of CaM were necessary for the Ca(2+)-dependent shift. However, channel activity induced by the CaM mutants showed Ca(2+)-dependent decrease, implying a Ca(2+) sensor existing besides CaM. These results suggest that both N- and C-lobes of CaM are required for the Ca(2+)-dependent regulations of Ca(V)1.2 Ca(2+) channels.
Guo
Feng
F
Department of Pharmaceutical Toxicology, School of Pharmaceutical Sciences, China Medical University, 92 Beier Road, Shenyang 110001, China.
Minobe
Etsuko
E
Yazawa
Kazuto
K
Asmara
Hadhimulya
H
Bai
Xiao-yan
XY
Han
Dong-yun
DY
Hao
Li-ying
LY
Kameyama
Masaki
M
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002147:Calmodulin / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D006168:Guinea Pigs; D006801:Humans; D018408:Patch-Clamp Techniques; D017434:Protein Structure, Tertiary / Q000235:genetics
D020746:Calcium Channels, L-Type; D002147:Calmodulin; C419385:L-type calcium channel alpha(1C); D002118:Calcium