Ca(V)1.2 and Ca(V)1.3 L-type calcium channels regulate the resting membrane potential but not the expression of calcium transporters in differentiated PC12 cells.

PC12 cells differentiated under the influence of the neuronal growth factor (NGF) serve as a model of both sympathetic neurons and chromaffin cells. NGF-induced differentiation critically depends on elevated intracellular calcium concentration. Main pathway for Ca²⁺ entry in excitable cells is represented by voltage-dependent calcium channels including L-type calcium channels (LTCC). We investigated role of Ca(V)1.2 and Ca(V)1.3 LTCC subtypes in NGF-differentiated PC12 cells. The expression of LTCC subtypes was downregulated by transfection of NGF-differentiated PC12 cells with siRNA for either CACNA1C or CACNA1D gene. Efficiency of gene silencing was verified by RT-PCR and by functional essay. The dominant LTCC subtype in PC12 cells was Ca(V)1.2. Downregulation of either LTCC significantly hyperpolarized the resting membrane potential. Expression of mRNA for intracellular calcium transporters inositol trisphosphate receptor type 1, 2 and 3, ryanodine receptor type 1 and 2 and sarco/endoplasmic reticulum Ca²⁺ ATPase type 2 as well as plasma membrane transporters Na⁺-Ca²⁺ exchanger type 1 and 2 was not altered in the absence of either LTCC subtype. In conclusion, Ca²⁺ influx through Ca(V)1.2 or to Ca(V)1.3 channel subtypes contributes to maintenance of the resting membrane potentials of NGF-differentiated PC12 cells but is not required for regulation of expression of genes for calcium-transporting proteins.