Testing the roles of motoneuron membrane currents for behaviorally adequate motor output by targeted genetic manipulations of an identified flight motoneuron in Drosophila

• Applicant: Dr. Stefanie Ryglewski
• Subject Area: Molecular Biology and Physiology of Neurons and Glial Cells
• Term: from 2009 to 2011
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 133714411

• Final Report Year: 2012

Final Report Abstract

Different blends of membrane currents underlie distinct functions of neurons in the brain. A major step towards understanding neuronal function, therefore, is to identify the genes that encode different ionic currents. This study combined in situ patch clamp recordings of somatodendritic calcium currents in an identified adult Drosophila motoneuron with targeted genetic manipulation. Voltage clamp recordings revealed transient LVA currents with activation between -60 mV and -70 mV as well as HVA current with an activation voltage around -30 mV. LVA could be fully inactivated by prepulses to -50 mV and was partially amiloride-sensitive. Recordings from newly generated mutant flies demonstrated that Dm alphaG (Cav3 homolog) encoded the amiloride-sensitive portion of the transient LVA calcium current. We further demonstrated that the Cav2 homolog, Dmca1A, mediated the amiloride-insensitive component of LVA current. This novel role of Cav2 channels was substantiated by patch clamp recordings from conditional mutants, RNAi knock-downs, and following Dmca1A overexpression. In addition, we show that Dmca1A underlies the HVA somatodendritic calcium currents in vivo. Therefore, the Drosophila Cav2 homolog, Dmca1A, underlies HVA and LVA somatodendritic calcium currents in the same neuron. Interestingly, DmαG is required for regulating LVA and HVA derived from Dmca1A in vivo. In sum, each vertebrate gene family for voltage gated calcium channels is represented by a single gene in Drosophila, namely Dmca1D (Cav1), Dmca1A (Cav2), and Dm alphaG (Cav3), but the commonly held view that LVA calcium currents are usually mediated by Cav3 rather than Cav2 channels may require reconsideration.

Publications

• (2009) Shaker and Shal mediate transient calcium-independent potassium current in a Drosophila flight motoneuron. J Neurophysiol 102(6):3673-88
  Ryglewski S, Duch C
  
• (2011) Cav2 Channels Mediate LVA and HVA Calcium Currents in Drosophila Motoneurons. J Physiol Dec 19
  Ryglewski S, Lance K, Levine RB, Duch C