XB-ART-11374
Neuron
2000 Jan 01;251:177-90. doi: 10.1016/s0896-6273(00)80881-8.
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The I-II loop of the Ca2+ channel alpha1 subunit contains an endoplasmic reticulum retention signal antagonized by the beta subunit.
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The auxiliary beta subunit is essential for functional expression of high voltage-activated Ca2+ channels. This effect is partly mediated by a facilitation of the intracellular trafficking of alpha1 subunit toward the plasma membrane. Here, we demonstrate that the I-II loop of the alpha1 subunit contains an endoplasmic reticulum (ER) retention signal that severely restricts the plasma membrane incorporation of alpha1 subunit. Coimmunolabeling reveals that the I-II loop restricts expression of a chimera CD8-I-II protein to the ER. The beta subunit reverses the inhibition imposed by the retention signal. Extensive deletion of this retention signal in full-length alpha1 subunit facilitates the cell surface expression of the channel in the absence of beta subunit. Our data suggest that the beta subunit favors Ca2+ channel plasma membrane expression by inhibiting an expression brake contained in beta-binding alpha1 sequences.
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