Reduction of insulin secretion in the insulinoma cell line INS-1 by overexpression of a Cav23 (α1E) calcium channel antisense cassette

Objective: Multiple types of voltage-activated Ca2+ channels (T, L, N, P, Q and R type) coordinate a variety of Ca2+-dependent processes in neurons and neuroendocrine cells. in insulinoma cell lines as well as in endocrine tissues, the non-L-type alpha1E (Ca(v)2.3) subunit is expressed as the tissue-specific splice variant alpha1Ee. Design and Methods: To understand the functional role of alpha1E-containing Ca2+ channels, antisense alpha1E mRNA was overexpressed in INS-1 cells by stable transfection of an antisense alpha1E cassette cDNA. As controls, either a sense alpha1E cassette or a control vector containing enhanced green fluorescent protein as an unrelated gene was stably transfected. The overexpression of each transfected cassette cDNA was recorded by RT-PCR. Results: In three independent antisense a alpha1E INS-1 clones, the glucose-induced insulin release was significantly reduced as compared with wild-type INS-1 cells and with a sense alpha1E INS-1 clone. However, in the antisense INS-1 clones, the KCl-induced insulin release was less impaired by overexpressing the antisense alpha1E cassette than the glucose-induced insulin release, leading to the assumption that glucose (15 mmol/1) and KCl (2 5 mmol/l) finally depolarize the membrane potential to a different extent. Conclusion: alpha1E is involved in glucose-induced insulin secretion probably by influencing the excitability of INS-1 cells.