Distribution of voltage gated calcium channel β subunits in the mouse retina

Abstract

Voltage gated calcium channels (VGCCs) are essential to neuronal excitation and signal transduction. They are multimeric in structure and comprised of an alpha subunit that functions as a calcium pore and two additional subunits: an alpha2delta subunit and a cytoplasmic beta subunit. To better understand the role of VGCCs in the retina we used immunohistochemical methods to determine the distribution of VGCC β subunits in normal and mutant mice. To verify the specificity of each antibody and to examine the potential for subunit redistribution when beta subunit expression is perturbed, we used 4 mutant mouse lines that each lack a specific β subunit isoform (β 1–β 4). We found the β 1 subunit distributed on cell bodies in the inner nuclear layer (INL) and on processes within both the inner and outer limiting membrane; the β 2 subunit localized to the outer plexiform layer (OPL) and inner plexiform layer (IPL); the β 3 subunit was localized to three narrow and distinct bands within the IPL; the β 4 subunit was localized to three diffuse bands within the IPL. Loss of one β subunit affected labeling intensity but not general distribution patterns of other β subunits. It is likely that VGCCs critical for retinal signal transmission are comprised of the β 2 subunit in the OPL and any of the 4 β subunits in the IPL. Our results suggest that within the OPL the α 1F subunit pairs predominantly with the β 2 subunit while within the IPL it may pair with either any β subunit.