Antisense depletion of beta‐subunits modulates the biophysical and pharmacological properties of neuronal calcium channels.

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Abstract
1. The role of the voltage‐dependent calcium channel (VDCC) beta‐subunit has been examined in cultured rat dorsal root ganglion neurones (DRGs). An antipeptide antibody was raised and this recognized proteins corresponding to beta‐subunits in a number of preparations. Immunoreactivity for the VDCC beta‐subunit in DRGs was concentrated on the internal side of the plasma membrane but was also present in the cytoplasm. 2. A twenty‐six‐mer antisense oligonucleotide with homology to all published VDCC beta‐subunit sequences was microinjected into individual cells, and maximal depletion of VDCC beta‐subunit immunoreactivity was observed after 108 h suggesting a half‐life for the turnover of the beta‐subunit greater than 50 h. No depletion was obtained with nonsense oligonucleotide. 3. The effect of depletion of VDCC beta‐subunit immunoreactivity on calcium channel currents in these cells was a reduction in amplitude of the maximum current of about 47%, and a shift in the voltage dependence of current activation of about +7 mV. These effects are the converse of those observed following co‐expression of cloned beta‐ with alpha 1‐subunits in oocytes and other expression systems. 4. The ability of the 1,4‐dihydropyridine (DHP) agonist Bay K 8644 to enhance calcium channel currents was greatly reduced following depletion of beta‐subunit immunoreactivity. This result is in agreement with the finding in several systems that co‐expression of the beta‐subunit with alpha 1‐subunits results in an increased number of DHP binding sites. 5. These results show that calcium channel beta‐subunits form part of native neuronal calcium channels and modify their biophysical and pharmacological properties.