Different functions of two putative Drosophila α2δ subunits in the same identified motoneurons

Abstract

Voltage gated calcium channels (VGCCs) regulate neuronal excitability and translate activity into calcium dependent signaling. The α1 subunit of high voltage activated (HVA) VGCCs associates with α2δ accessory subunits, which may affect calcium channel biophysical properties, cell surface expression, localization and transport and are thus important players in calcium-dependent signaling. In vertebrates, the functions of the different combinations of the four α2δ and the seven HVA α1 subunits are incompletely understood, in particular with respect to partially redundant or separate functions in neurons. This study capitalizes on the relatively simpler situation in the Drosophila genetic model containing two neuronal putative α2δ subunits, straightjacket and CG4587, and one Cav1 and Cav2 homolog each, both with well-described functions in different compartments of identified motoneurons. Straightjacket is required for normal Cav1 and Cav2 current amplitudes and correct Cav2 channel function in all neuronal compartments. By contrast, CG4587 does not affect Cav1 or Cav2 current amplitudes or presynaptic function, but is required for correct Cav2 channel allocation to the axonal versus the dendritic domain. We suggest that the two different putative α2δ subunits are required in the same neurons to regulate different functions of VGCCs.