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  • Title: Both N- and C-lobes of calmodulin are required for Ca2+-dependent regulations of CaV1.2 Ca2+ channels.
    Author: Guo F, Minobe E, Yazawa K, Asmara H, Bai XY, Han DY, Hao LY, Kameyama M.
    Journal: Biochem Biophys Res Commun; 2010 Jan 08; 391(2):1170-6. PubMed ID: 20006578.
    Abstract:
    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.
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