Membrane-localized ?-subunits alter the PIP2 regulation of high-voltage activated Ca2+ channels.

ABSTRACT: The ?-subunits of voltage-gated Ca(2+) (Ca(V)) channels regulate the functional expression and several biophysical properties of high-voltage-activated Ca(V) channels. We find that Ca(V) ?-subunits also determine channel regulation by the membrane phospholipid phosphatidylinositol 4,5-bisphosphate (PIP(2)). When Ca(V)1.3, -2.1, or -2.2 channels are cotransfected with the ?3-subunit, a cytosolic protein, they can be inhibited by activating a voltage-sensitive lipid phosphatase to deplete PIP(2). When these channels are coexpressed with a ?2a-subunit, a palmitoylated peripheral membrane protein, the inhibition is much smaller. PIP(2) sensitivity could be increased by disabling the two palmitoylation sites in the ?2a-subunit. To further test effects of membrane targeting of Ca(V) ?-subunits on PIP(2) regulation, the N terminus of Lyn was ligated onto the cytosolic ?3-subunit to confer lipidation. This chimera, like the Ca(V) ?2a-subunit, displayed plasma membrane localization, slowed the inactivation of Ca(V)2.2 channels, and increased the current density. In addition, the Lyn-?3 subunit significantly decreased Ca(V) channel inhibition by PIP(2) depletion. Evidently lipidation and membrane anchoring of Ca(V) ?-subunits compete with the PIP(2) regulation of high-voltage-activated Ca(V) channels. Compared with expression with Ca(V) ?3-subunits alone, inhibition of Ca(V)2.2 channels by PIP(2) depletion could be significantly attenuated when ?2a was coexpressed with ?3. Our data suggest that the Ca(V) currents in neurons would be regulated by membrane PIP(2) to a degree that depends on their endogenous ?-subunit combinations.

SUBMITTER: Suh BC 

PROVIDER: S-EPMC3287006 | biostudies-literature | 2012 Feb

REPOSITORIES: biostudies-literature