Key result
Replacement of Ser1901 by Ala abolished the PKA-mediated enhancement of L-type Ca2+ channel currents by forskolin, but not the negative shift of the activation curve.
Ser1901 is essential for PKA-mediated enhancement of L-type calcium channel currents, while the voltage-dependence of activation is modulated via a different site.
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Ser1901 mutation selectively disrupts PKA current enhancement in animal channels; leaves open distinct sites for voltage shift and human translation.
Cardiac L-type Ca(2+) channel is facilitated by protein kinase A (PKA)-mediated phosphorylation. Here, we investigated the role of Ser(1901), a putative phosphorylation site in the carboxy-terminal of rat brain type-II alpha(1C) subunit (rbCII), in the PKA-mediated regulation. Forskolin (3 microM) enhanced Ca(2+) channel currents (I(Ca)) and shifted the activation curve to negative voltages, which were abolished by protein kinase inhibitor. Replacement of Ser(1901) of rbCII by Ala abolished the enhancement of I(Ca) by forskolin but not the shift of the activation curve. These results indicate that Ser(1901) is required for the PKA-mediated enhancement of I(Ca), and that the voltage-dependence of the activation of I(Ca) appears to be modulated via another PKA phosphorylation site.
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Naguro et al. (2001) studied this question. Ser1901 mutation to Ala / Forskolin was evaluated on Ca2+ channel currents (ICa) and activation curve shift. Replacement of Ser1901 by Ala abolished the PKA-mediated enhancement of L-type Ca2+ channel currents by forskolin, but not the negative shift of the activation curve.
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